University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Gas diffusion

Classification: Manifold process -> Gas diffusion

Citations 227

"Determination Of Sulfur Dioxide In Wines By Gas-diffusion Flow Injection Analysis Utilizing Modified Electrodes With Electrostatically Assembled Films Of Tetraruthenated Porphyrin"
Anal. Chim. Acta 1999 Volume 387, Issue 2 Pages 175-180
Carla M. N. Azevedo, Koiti Araki, Henrique E. Toma and Lúcio Angnes

Abstract: Reported is a new method for the determination of both Gee and total SO2 in wine, specially designed for FIA. The method involves separation of the analyte using a flow-through gas diffusion unit, in line with an amperometric detector consisting of a glassy carbon electrode modified with electrostatically assembled films of a tetraruthenated porphyrin. The results demonstrate a good accuracy, comparable with those obtained using the conventional iodometric method. In addition, the method can be readily applied to red, white and rose wines; it is free from interference of the other compounds of wine, consumes small amounts of sample and is faster than the iodometric method.
Sulfur dioxide Wine Red Wine White Wine Rose Electrode

"Determination Of Sulfur Dioxide And Ascorbic Acid In Beverages Using A Dual Channel Flow Injection Electrochemical Detection System"
Anal. Chim. Acta 2000 Volume 416, Issue 1 Pages 105-110
Terence J. Cardwell and Melinda J. Christophersen

Abstract: A new flow injection method is described for the simultaneous determination of ascorbic acid (AA) and sulfur dioxide in red and white wines and various fruit juices. The flow injection manifold consists of a dual channel amperometric detection system, where AA is detected at a glassy carbon electrode set at +0.42 V (versus Ag/AgCl) and sulfur dioxide is detected at a platinum electrode at +0.90 V (versus Ag/AgCl) after separation by a gas diffusion unit. In the application of this method to the analysis of both analytes in wines and fruit juices, the results for white wines, fruit juices and juice concentrates agree well with data obtained by ion-exclusion chromatography. However, in the case of red wines and a sweet white wine, it is necessary to extract the analytes using solid phase extraction on a quaternary amine SAX cartridge before acceptable results are achieved by the new flow injection method. The linear dynamic range for AA is 3-50 mg/l with a detection limit of 1.5 mg/l and for sulfur dioxide the linear range is 0.25-15 mg/l with a detection limit of 0.05 mg/l. The sampling frequency for both analytes is 30/h.
Ascorbic acid Sulfur dioxide Wine Red Wine White Amperometry Electrode Electrode

"Flow Injection Analysis Of Kjeldahl Nitrogen In Milk And Dairy Products By Potentiometric Detection"
Anal. Chim. Acta 1999 Volume 385, Issue 1-3 Pages 437-441
José F. C. C. Lima, Cristina Delerue-Matos and M. Carmo Vaz

Abstract: A flow injection analysis (FIA) system with a potentiometric tubular detector and a gas diffusion unit was developed for the determination of Kjeldahl nitrogen in milk and dairy products. The samples were digested by the Kjeldahl method and afterwards injected into the RA system without prior treatment. NaOH solution was introduced into the system to promote the conversion of ammonium ions to ammonia gas. The gas produced diffused through a gas-permeable membrane towards an acceptor channel (Tris-HCl, pH=7.5). When in contact with this solution, ammonia gas was reconverted to ammonium cation and carried to a tubular electrode sensitive to this species. Therefore, a PVC tubular ammonium ion-selective electrode was prepared without inner reference solution and with the sensor system based on nonactine and monactine dissolved in Tris-(2-ethylhexyl) phosphate. The results obtained with the developed FIA system were in good agreement with those of the reference method the relative deviations being less than 4%. Reproducibility of the method was assessed by the relative standard deviation, which was always less than 0.5% for 12 consecutive injections of sample digests. A sampling rate of 100 samples h-1 was obtained.
Ammonia Dairy Products Potentiometry Electrode

"Studies Of Selectivity In The Amaranth Method For Chlorine Dioxide"
Talanta 2000 Volume 51, Issue 5 Pages 879-888
Gary L. Emmert, David E. Coutant, Deborah L. Sweetin, Gilbert Gordon and Bernard Bubnis

Abstract: Studies were designed to evaluate the amaranth method for measuring chlorine dioxide in water. Specifically, the effects of pH and temperature are examined for the amaranth method. The results of interference studies are reported for free available chlorine species, chlorite ion, chlorate ion, iron (III) ion, oxidized manganese, and monochloramine. Additional research focused on selectivity enhancement for chlorine dioxide over free available chlorine using ammonia/ammonium chloride buffer and gas diffusion-flow injection analysis. The results of method detection Emit and accuracy and precision studies are reported for measuring chlorine dioxide in the presence of free available chlorine.

"Ozone And Chlorine Dioxide: Similar Chemistry And Measurement Issues"
Ozone Sci. Eng. 1999 Volume 21, Issue 5 Pages 447-464
Gilbert Gordon; Bernard Bubnis

Abstract: The chemical reactions associated with ozone and chlorine dioxide can be complicated and involve numerous intermediates. When ozone is applied, the presence of reactive intermediate species (O-2(-), O-3(-), OH, HO2, HO2-, and H2O2) influence the extent of oxidation that takes place and determines the amount and types of by-products formed. Similarly, when chlorine dioxide is applied the amount of intermediate (Cl2O2) formed determines whether chlorine dioxide producing reactions or chlorate ion forming reactions occur. Ozone and chlorine dioxide are excellent agents for inactivating Cryptosporidium and Giardia. Microbiologically, each of the agents are very reactive. In the case of ozone, typically each molecule undergoes a one-electron change. The mechanism of chlorine dioxide inactivation involves a recycling process whereby chlorine dioxide is reduced to chlorite ion followed by the regeneration of chlorine dioxide that continues to react within the cell over and over again. Chlorite ion also has oxidizing power and in some cases, is a biocide. When ozone and chlorine dioxide are used in combination, it is important that the chlorine dioxide application follow the ozone treatment to prevent the formation of unwanted by-products such as ClO3-.
Ozone

"Gas Diffusion Flow Injection Determination Of Ammonium Ions In River And Waste Waters By Conductometry"
Collect. Czech. Chem. Commun. 1999 Volume 64, Issue 12 Pages 1966-1974
Jiri VLCEK and Vlastimil KUBAN

Abstract: An FIA conductometric method for monitoring of ammonium ions in river and waste waters is proposed. A very good detection limit (x(D) 5.6 µmol l-1) was obtained at 100/20 s pre-concentration/rinsing times and 2 mL sample consumption per analysis at the flow rate 0.8 mL min-1. The detection limit x(D) can be further improved at longer pre-concentration/rinsing times. Precipitation of polyvalent metal ions (mainly Fe(III)) was eliminated by addition of 0.5 mmol L-1 EDTA prior to injection. The results are comparable with those obtained by spectrophotometry (Nesslers reagent).

"Sequential Determination Of Free And Total Cyanide By Flow Injection"
J. Autom. Methods Manag. Chem. 1999 Volume 21, Issue 1 Pages 23-26
Maria Angélica Bonadiman Martin, Edgard Moreira Ganzarolli, Arilson Lehmkuhl, Ivan Gonçalves de Souza, and Roldão Roosevelt Urzêdo de Queiróz

Abstract: This study presents a flow injection system for the sequential determination of free (CN-) and total (CN-+ HCN) cyanide using a potentiometric method which employs two different processes for the determination of these two chemical species. The first process is based on direct detection of CN-using an ion-selective electrode for cyanide. In the second process, the sample is mixed with acid, and the released HCN is transferred across a PTFE membrane. The flow system employs three solenoid valves, a gas diffusion chamber, an ion-selective electrode, a potentiometer, and a computer with an AID conversion card. A Turbo Pascal(R) computer program automatically performs all the steps involved in data acquisition and processing. The standard deviation far the results obtained with the proposed method was 0.5%.
Cyanide, free Cyanide, total Electrode

"Determination Of Ethanol In Wines By Flow Injection Spectrophotometry Using Gas-diffusion And An Immobilized Enzyme Reactor"
Am. J. Enol. Vitic. 1999 Volume 50, Issue 3 Pages 259-263
António O. S. S. Rangel and Ildikó V. Tóth

Abstract: A flow injection analysis (FIA) system for the spectrophotometric determination of ethanol in wines using an immobilized alcohol dehydrogenase reactor was developed. A gas diffusion unit was used to achieve a large dilution and to separate ethanol from the matrix. This way, the contact of the sample with the reactor was avoided and possible interferences in the spectrophotometric measurements were significantly reduced. The alcohol dehydrogenase enzyme was immobilized on alkylaminated controlled pore glass, and the consumption of the NAD cofactor was minimized (0.6 µmol per assay) by using the merging zone technique. The detection limit was 0.4% (v/v). Good precision was achieved, with relative standard deviations less than 2.2% (n = 9). For 20 samples of different types of table and Port wines, the results showed good agreement with the OIV usual procedure, the relative deviation being less than 4.4%. Thirty determinations per hour can be carried out within the ethanol concentration range of 5% to 25% (v/v), without any sample pretreatment.
Ethanol Port Spectrophotometry

"Multisyringe Flow System: Determination Of Sulfur Dioxide In Wines"
Analyst 2000 Volume 125, Issue 8 Pages 1501-1505
Marcela A. Segundo, António O. S. S. Rangel, Andreu Cladera and Víctor Cerdà

Abstract: A multisyringe flow system for the spectrophotometric determination of sulfur dioxide in wines is described. The methodology is based on the well-known reaction among SO2, formaldehyde and pararosaniline. The proposed manifold also includes a gas diffusion unit in order to prevent the color interference of red wines in the spectrophotometric measurement. The proposed method was successfully applied to the determination of free SO2 (2-75 mg l-1) and total SO2 (10-250 mg l-1) in wines, just by changing a few operating parameters in the controlling software. A sampling-rate of 25-30 samples per hour was achieved with good repeatability for 10 consecutive injections of wine samples (RSD < 3.2%). The results obtained from 10 wine samples for each determination were statistically comparable to those obtained by the recommended procedure.
Sulfur dioxide Wine Red Spectrophotometry

"Potentiometric Determination Of Glucose By Enzymatic Oxidation In A Flow System"
Anal. Chim. Acta 1979 Volume 105, Issue 1 Pages 43-52
Lo Gorton and Khan M. Bhatti

Abstract: A potentiometric determination is described for glucose based on oxidation by 1,4-benzoquinone with immobilized glucose oxidase as catalyst in an enzyme reactor. The electrode is preceded by an analytical dialysis unit to remove proteins. The ratio of quinone to hydroquinone was measured with a flow-through gold electrode. Another gold electrode preceded the enzyme reactor to correct for serum components (e.g. ascorbic acid) which can also reduce quinone. The operating range is 0.04-10 x 10^-3 M β-D-glucose. The dialysis proceeds with a linear dependence on glucose concentration, and the dialysis ratio can be adjusted by changing the buffer flow rate.
Glucose Clinical analysis Electrode Electrode Potentiometry

"Continuous Removal Of Oxygen From Flowing Solutions"
Anal. Chim. Acta 1980 Volume 121, Issue 1 Pages 23-28
A. Troj&aacute;nek and K. Holub

Abstract: An apparatus for continuous removal of oxygen or other dissolved gases from liquid samples is described; it is useful in continuous analyzes. The gas diffuses through a semipermeable membrane into a space with a lower partial pressure of the particular gas. The separation unit consists of two concentric tubes and is practical and efficient. The mathematical model for transport under conditions of stationary gas diffusion with laminar flow of the liquid in the tube did not correspond satisfactorily to the experimental relationship, probably because of turbulence in the flow.
Potentiometry

"Determination Of Oxidized Ketone Bodies In Milk By Flow Injection Analysis"
Anal. Chim. Acta 1983 Volume 149, Issue 1 Pages 281-289
Peter Marstorp, Torbj&ouml;rn Anf&auml;ltLennart Andersson

Abstract: A flow injection method is described for the determination of oxidized ketone bodies in milk. Acetoacetate is decarboxylated to acetone at 100°C. Acetone is separated from the sample by gas diffusion through a teflon membrane and measured spectrophotometrically. The detection limit is 0.1 mM. Accuracy and reproducibility are good up to 5 mM. The sample capacity is up to 100 samples/h.
Acetone Ketones Milk Spectrophotometry

"Membrane Separation In Flow Injection Analysis. Gas Diffusion"
Anal. Chim. Acta 1983 Volume 151, Issue 1 Pages 359-369
W. E. Van Der Linden

Abstract: A general expression is derived for the membrane transport process in a flow-through unit as commonly used in flow injection systems. The validity of the formulae was tested for gas-diffusion membranes by using compounds with different volatilities such as ammonia, carbon dioxide and acetic acid. Several microporous hydrophobic membranes were tested. A new module design is proposed.
Acetic acid Ammonia Carbon dioxide Water Spectrophotometry

"Determination Of Total Ammoniacal Nitrogen In Water By Flow Injection Analysis And A Gas Diffusion Membrane"
Anal. Chim. Acta 1983 Volume 153, Issue 1 Pages 271-275
M. van Son, R. C. Schothorst and G. den Boef

Abstract: The sample (29 µL) is injected into a 10 mM NaOH carrier stream (0.72 mL min-1) and passes to a dialyser module fitted with a PTFE gas-permeable membrane. The NH3 released diffuses through the membrane and is absorbed in a parallel stream of 0.1 mM bromothymol blue (pH 6.5), and the absorbance of the resulting solution is measured at 620 nm. The change in absorbance of the indicator solution varies rectilinearly with the concentration. of NH3 in the sample within the range 1 µM to 0.1 mM, and the limit of detection is ~1 µM. Results for canal water (~65 µM-NH3) agreed well with those by the Nessler method. The sampling rate is 100 h-1. Carbon dioxide interferes seriously, but the method has the advantage that clarification of turbid samples is unnecessary.
Ammonium, nitrogen Canal Spectrophotometry

"The Optimum Composition Of PH-sensitive Acceptor Solutions For Membrane Separation In Flow Injection Analysis"
Anal. Chim. Acta 1983 Volume 155, Issue 1 Pages 273-277
W. E. van der Linden

Abstract: A theoretical study is presented of factors governing the choice of indicator and buffer systems for the spectrophotometric determination of volatile analytes (e.g., NH3 and CO2) by transfer across a gas-permeable membrane into a suitable acceptor solution Application of the derived equations is illustrated by the choice of optimum conditions for the measurement of 0.1 to 10 mM NH3
Ammonia Carbon dioxide Spectrophotometry

"Polymer-membrane PH Electrodes As Internal Elements For Potentiometric Gas-sensing Systems"
Anal. Chim. Acta 1983 Volume 155, Issue 1 Pages 11-20
W. N. Opdycke, S. J. Parks and M. E. Meyerhoff

Abstract: The use of a pH-responsive polymer, based on tridodecylamine incorporated in a PVC matrix, was studied for the fabrication of low-cost NH3- and CO2-sensing electrodes for, e.g., detection in biochemical analysis. Miniature static gas sensors were constructed either (i) with or (ii) without internal reference solution In (i) an earlier design (cf. Meyerhoff et al., Anal. Abstr., 1983, 44, 3D29) was used, and in (ii) the membrane was coated directly on to a graphite rod. Under optimum conditions such static sensors exhibited rectilinear responses with slopes of 48 to 62 mV per decade, and potentials were reproducible to within ±1.5 mV at gas concentration. >1 mM. For automated continuous-flow systems, tubular forms of the polymer-membrane electrodes and a simple flow-through gas-dialysis arrangement were used (cf. Anal. Chem., 1981, 53, 992). The polymer-based sensors provide an attractive alternative to gas-sensing devices based on conventional glass pH electrodes.
Ammonia Carbon dioxide Biochemical analysis Electrode Electrode Potentiometry

"Integrated Microconduits For Flow Injection Analysis"
Anal. Chim. Acta 1984 Volume 161, Issue 1 Pages 1-25
Jaromir Rika and Elo H. Hansen

Abstract: The novel continuous-flow arrangement described is little larger than a credit card, and the channels linking the injection unit, mixing coils, dialysis or diffusion units and detectors are fabricated by impression or engraving into a block (7 cm x 4.5 cm x 1.0 cm) of transparent PVC. Connections to one or more detectors are provided. The versatility of the arrangement is demonstrated for a number of flow injection systems with integrated potentiometric or optical detectors and with integrated gas diffusion or ion-exchange units.
Calcium pH Ion exchange Potentiometry Spectrophotometry

"Rapid Determination Of Sulfide In Waste Waters By Continuous-flow Analysis And Gas Diffusion And A Potentiometric Detector"
Anal. Chim. Acta 1984 Volume 163, Issue 1 Pages 293-297
K. Brunt

Abstract: The system is based on a flow-through gaseous diffusion unit and potentiometric determination with a S2--selective electrode. In the range 0.5 to 600 ppm of S2-, the mean response is 30.2 mV per decade. The sampling rate is ~15 h-1, and the efficiency of transfer across the PTFE membrane is 48%. At S2- concentration. <50 ppm, the results obtained agreed well with those by a distillation method. Apparent losses at higher concentration. in the proposed method are ascribed to incorrect sample storage, problems of which are discussed.
Sulfide Waste Electrode Potentiometry

"Optosensing At Active Surfaces - A New Detection Principle In Flow Injection Analysis"
Anal. Chim. Acta 1985 Volume 173, Issue 1 Pages 3-21
Jaromir Rika and Elo H. Hansen

Abstract: Detection in micro-channel flow injection analysis by the interaction of radiation with a surface situated in the flowing stream has been explored by the initial application of reflectance spectrophotometry, the principles of which are discussed. For pH measurement, a plug of fibrous cellulose to which an acid - base indicator was covalently bound (Merck Universal, Neutralit and Spezial non-bleeding indicator papers) was mounted in the integrated flow-through optosensor (cf. Ibid., 1984, 161, 1) adjacent to the end of the optical fiber. A standard deviation (n = 7) of 0.004 at pH 7.2 and a sampling rate of 120 h-1 could be attained. For the determination of NH3, and of urea after reaction with urease, a white opaque porous hydrophobic membrane is mounted transversely adjacent to the end of the optical fiber; the NH3 diffuses through the membrane and meets a stream of bromothymol blue solution. A new injection technique is also described.
Ammonia pH Urea Spectrophotometry

"Selectivity Enhancement By Flow Injection Analysis"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 259-267
G. E. Spacey, D. A. Hollowell, K. G. Miller, M. R. Straka and G. Gordon

Abstract: Flow injection analysis was used to improve the selectivity of several existing methods. By kinetic discrimination, O3 is determined by the decolorization of indigo blue at 600 nm with a coefficient of variation of <1%, and ClO2 is determined by chemiluminescence with luminol, each in the presence of Cl. Chlorate can be determined by its reaction with I- in 12 M HCl, the absorbance being measured at 370 nm. The detection limit is 1 µM and the coefficient of variation are <5%. Chlorite and ClO3- are determined by injecting 12 M HCl in front of the sample and a carrier solution of pH 4.0 after it, thus forming two peaks, the first of which corresponds to total ClO3- and ClO2- and the second to ClO2- only. A dual-phase gas diffusion system for hydride generation provides a significant decrease in interference by transition metals.
Arsenic Chlorite Ozone Chlorate ion Chlorine dioxide Chemiluminescence Spectrophotometry Spectrophotometry Sample preparation

"Determination Of Sulfur Dioxide By Flow Injection Analysis With Amperometric Detection"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 445-451
M. Granados, S. Maspoch and M. Blanco

Abstract: The SO2 is determined by direct injection or after separation in a diffusion cell with a PTFE membrane. The detection cell is of wall-jet type with vitreous-carbon working and auxiliary electrodes and silver - AgCl reference electrode. With the diffusion cell at 25°C the response shows two rectilinear ranges between 0.06 and 6 mg L-1 and 12 and 110 mg l-1, and at 50°C the range is from 0.04 to 5 mg l-1. The coefficient of variation at 3 mg L-1 are 1.7 and 2.3% (n = 7) with detection limits of 0.03 and 0.02 mg L-1 at 25°C and 50°C, respectively. Sulfide and NO2- interfere at mg L-1 levels. The method is applied to the determination of free SO2 in wine.
Sulfur dioxide Wine Amperometry Electrode Electrode

"Flow Injection Determination Of Ammonia In Kjeldahl Digests By Gas Diffusion And Conductometry"
Anal. Chim. Acta 1987 Volume 193, Issue 1 Pages 19-27
Celio Pasquini and Lourival Cardoso de Faria

Abstract: The digest (100 µL) was injected into a stream of water (1.6 mL min-1) and mixed with a stream of 2 M or 3 M NaOH containing 1% of EDTA (1.6 mL min-1) at ambient temperature The resulting stream was passed (3.2 mL min-1) to a diffusion cell and the NH3 was allowed to diffuse through a PTFE membrane into a second water stream, which was passed into a flow cell for conductometric determination of NH3. The manifold was constructed from polyethylene tubing (0.8 mm i.d.). There was no interference from 1.25 M H2SO4, 7 to 30 g L-1 of K2SO4, 6 mM Ca(II), Fe(III), Al(III), Mg, Zn(II), Cu(II) or Se(IV) or 3 mM Hg(II) in the determination of 2 mM or 3 mM NH3. The method was applied to samples of vegetables, animal feeds and fertilizers, and results agreed with those by a distillation - titration method. In the determination of 1 to 4% of N the coefficient of variation (n = 5) was 1%. The sampling rate was ~100 h-1.
Ammonia Feed Commercial product Vegetable Conductometry

"Spectrophotometric Determination Of Total Cyanide In Waste Waters In A Flow Injection System With Gas Diffusion Separation And Preconcentration"
Anal. Chim. Acta 1987 Volume 198, Issue 1 Pages 25-36
Zhaohai Zhu and Zhaolun Fang

Abstract: The rapidity of the cited determination was improved by use of the unstable red intermediate product of the reaction of CN- with isonicotinic acid(I) and 3-methyl-1-phenyl-2-pyrazolin-5-one(II), instead of the blue final product. The pH of waste water samples was adjusted to 11.5 to 13.0 before being merged with HCl containing 1,10-phenanthroline to give a pH of 6.4 to 7.4, and reaction at 60°C in a PTFE coil. The liberated HCN diffused through a PTFE separator membrane and was absorbed by NaOH solution This pre-concentrated solution was injected into NaOH carrier, merged with chloramine T and I - II reagents downstream, and the spectrophotometric peaks were recorded at 548 nm. For a 2 mL sample and a pre-concentration. factor of 3.5, the detection limit was 6 ng mL-1. At 0.5 µg mL-1, the coefficient of variation was 1.4% (n = 22). The phenanthroline minimized the interference from most metal ions except Co(II).
Cyanide, total Waste Spectrophotometry

"Determination Of Ammonium Ion In A Flow Injection System With A Gas Diffusion Membrane. Selection Of Optimal Conditions For The PH Indicator"
Anal. Chim. Acta 1988 Volume 208, Issue 1-2 Pages 81-90
Ryuji Nakata, Takayoshi Kawamura, Hiroyuki Sakashita and Akihiko Nitta

Abstract: Optimum conditions were determined for the spectrophotometric determination of NH4+ by flow injection analysis. A membrane-separation module was constructed from a PTFE membrane filter (80 µm thick; pore size 0.5 µm) tightly held between two PVC sheets acting as spacers, and contained between two clear acrylic plates. The donor solution used was 1 M NaOH. Portions of acceptor stock solution of bromocresol purple(I), bromothymol blue or cresol red, containing NH4Cl buffer if necessary and the pH being adjusted with NaOH, were deaerated to remove CO2 and then injected by using a Rheodyne PTFE rotary valve (type 50) with a loop volume of 132 µL. Maximum sensitivity was achieved by using 15 µM-I at pH 6.8 with a flow rate of 1.0 mL min-1. The effects of donor and acceptor flow rates and of ultrasonic radiation were investigated. A lowering of sensitivity allowed analysis of undiluted urine samples, with a sample rate of 60 h-1 for concentration. >10 µM, and 30 to 40 h-1 for concentration. of 0.3 to 10 µM. The method was more precise than that involving indophenol blue - thymol for the determination of NH4+ in rain and river water.
Ammonium Urine Rain River Spectrophotometry

"Optimization Of Parameters For Gas Diffusion Flow Injection Systems"
Anal. Chim. Acta 1988 Volume 209, Issue 1-2 Pages 157-163
J. S. Canham, G. Gordon and G. E. Pacey

Abstract: Solutions of ClO2 were used in the study. Slow flow rates for both acceptor and donor streams provided efficient transfer of the gas. Use of the counter-current flow mode enhanced signals and the best transport properties were achieved when pressures on both sides of the membrane were equal. Channel depths should be as shallow as possible to achieve optimum results and a spiral-shaped diffusion cell should be used. For reactive systems, stopped-flow, in which the acceptor stream is stopped but the donor stream is continuous, was the best.
Chlorine dioxide

"Automated Spectrophotometric Field Monitor For Water Quality Parameters. Determination Of Ammonia"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 401-407
J. Richard Clinch and Paul J. Worsfold, Frank W. Sweeting

Abstract: A manual flow injection manifold (illustrated) was incorporated into an automated field monitor as described previously (Anal. Abstr., 1988, 50, 6H74). Sample (0.7 mL min-1) and NaOH (0.7 mL min-1) were mixed online in a 50-cm reaction coil before introduction into the water carrier stream (0.7 mL min-1). The carrier stream then passed together with bromothymol blue solution into a gas diffusion cell and the acceptor stream flowed to a solid-state spectrophotometric detector for determination of total NH3 at 635 nm. The calibration graph was rectilinear obtained for up to 5000 µg L-1 of NH3 and the limit of detection was 17 µg l-1. The coefficient of variation (n = 6) were 0.7 to 2.1%. Results are presented for a three-day field trial.
Ammonia Environmental Spectrophotometry

"Flow Injection Determination Of Membrane-selected Organic Compounds"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 299-313
R. G. Melcher

Abstract: A membrane - flow injection system has been developed and optimum conditions established for separation of trace organic compounds in aqueous solution The system comprises a membrane made from Dow Corning Silastic medical-grade silicone rubber tubing, a sample loop and a spectrophotometric detector. A liquid extractant is pumped through the bore of the membrane tube directly to the detector. The membrane is incorporated into a cell (illustrated) connected directly to the extractant stream. The effects were studied of factors, such as membrane size, cell dimensions, extractant composition and carrier flow rate, on peak height and shape. Optimized conditions were evaluated for separation of phenols and neutral organic compounds.
Organic compounds Phenols Spectrophotometry Sample preparation

"Simultaneous Determination Of Cyanide And Thiocyanate By The Pyridine/barbituric Acid Method After Diffusion Through A Microporous Membrane"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 259-269
Akra Tanaka, keiji Mashiba and Toshio Deguchi

Abstract: A membrane module (described and illustrated) comprising microporous PTFE membrane tubing (1 mm i.d., max. pore size 3.5 µm, porosity 70%) inserted into larger PTFE tubing was incorporated into a flow system for simultaneous determination of CN- and SCN-. The CN- and SCN- diffused through the membrane wall from the H3PO4 donor stream to a buffer acceptor stream, which was then mixed with chloramine T and pyridine - barbituric acid solution in a 30-m reaction coil. The absorbance of the solution was measured at 580 nm. Total CN- plus SCN- was determined at pH 6.0 by using 0.5 M phosphate buffer solution and CN- was determined at pH 8.1 with 0.3 M carbonate buffer solution The SCN- was determined by difference. Calibration graphs were rectilinear for up to 500 and 100 µM for CN- and SCN-, respectively; corresponding detection limits and coefficient of variation (n = 5) at the 10 µM level were 0.3 µM and 1.0% and 0.2 µM and 1.5%. Bromine interfered at both pH 6.0 and 8.1; Fe(CN)64- and Fe(CN)63- only interfered at pH 8.1.
Cyanide Thiocyanate ion Spectrophotometry

"Online Separation And Preconcentration In Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 41-55
Zhaolun Fang, Zhaohai Zhu, Suchun Zhang, Shukun Xu, Lei Guo and Lijing Sun

Abstract: A review is presented of developments in flow injection analysis that involve separation and pre-concentration. by gas diffusion, ion exchange or liquid - liquid extraction. Several inorganic illustrations of each principle are given, mainly of their use as a preliminary stage before determination by AAS. (44 references).
Ammonia Beryllium Cerium Cobalt Cyanide Fluoride Mercury Nickel Selenium Vanadium Ion exchange Spectrophotometry Spectrophotometry Spectrophotometry Spectrophotometry Sample preparation

"Different Approaches To The Determination Of Ammonium Ions At Low Levels By Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 121-136
G. Schulze, C. Y. Liu, M. Brodowski and O. Elsholz, W. Frenzel, J. M&ouml;ller

Abstract: For determination of 1 µM-NH3 by flow injection analysis, an optimized gas diffusion system was used, with spectrophotometric or selective-electrode detection. The gas diffusion unit had channels 7.5 cm long, 2 mm wide and 0.2 mm deep. The spectrophotometric detection flow cell had 10 mm pathlength and a capacity of 8 or 18 µL. The selective electrode (0.7 mm diameter, surface area ~20 mm2) consisted of nonactin in PVC and was used with an Orion 90-02 double-junction reference electrode. Spectrophotometric detection with bromocresol purple provided a lower limit of 0.2 µM, but was subject to background interference from, e.g., CO2. The selective electrode provided Nernstian response for 1 to 100 µM, with a detection limit of ~0.1 µM.
Ammonium Potentiometry Spectrophotometry Electrode

"Determination Of Creatinine In Undiluted Blood Serum By Enzymatic Flow Injection Analysis With Optosensing"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 147-159
Mette Tranholm Jeppesen and Elo Harald Hansen

Abstract: For the determination of creatinine in serum, a flow injection system was used that included a packed-bed enzyme reactor containing creatinine deiminase bonded to CPG-10 controlled-pore glass to liberate NH4+, which was converted into NH3 and transferred via a gas-permeable membrane (Celgard 2500 polypropylene; 0.04 µm pores) to an indicator stream containing 0.04% bromothymol blue at pH 6.8 for spectrophotometric detection at 620 nm. Endogenous NH3 was either removed by inclusion of a pre-reactor containing CPG-10-bonded glutamate dehydrogenase [NAD(P)+] or was monitored in a parallel system in which the creatinine deiminase reactor was omitted to obtain a reagent blank. The carrier stream in the pre-reactor system was 50 mM Tris containing 5 mM 2-oxoglutaric acid, 2 mM NADH, 20 mM EDTA and 0.5 mM ADP, with a reagent stream of 0.2 M NaOH to provide pH of 11.9. In the reagent-blank system, the carrier stream contained 20 mM Na2B4O7 to give pH of 9.2. The operating range was up to 1 mM for NH3 and for creatinine. Enzymic conversion efficiency was 91 ± 2%, and within-run reproducibility was ±4%.
Creatinine Blood Serum Clinical analysis Spectrophotometry

"Flow Injection Systems For Sample Introduction In Mass Spectrometry"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 385-390
John S. Canham and Gilbert E. Pacey

Abstract: The applications were studied of flow injection systems either for direct introduction of an analyte into the MS instrument or to convert the analyte to a suitable form for detection. Diagrams of the systems used are presented. A ploy(methyl methacrylate) membrane separator was used with the quadrupole MS flow injection system and a PTFE membrane separator with the single-focusing magnetic-sector MS flow injection system. The selectivity and sensitivity of MS increased the applications of flow injection analysis. The determination of As and CHCl3 are studied as examples.
Arsenic Mass spectrometry

"Sequential Flow Injection Determination Of Cyanide And Weak Metal Cyanide Complexes With Flow-through Heterogeneous Membrane Electrodes"
Anal. Chim. Acta 1988 Volume 215, Issue 1-2 Pages 283-288
E. Figuerola, A. Florido, M. Aguilar and J. De Pablo, S. Alegret

Abstract: Two I--selective heterogeneous epoxy-based membrane flow-through electrodes were placed before and after a gas diffusion unit in a flow injection system for determination of free and total CN-. The CN--containing sample was injected into a KNO3 carrier solution and free CN- was determined by the first flow-through electrode. The solution was then treated with the HCl stream in the reaction coil. The HCN evolved passed through the gas-permeable membrane in the diffusion unit and was collected in an alkaline solution, where the CN- was measured by the second flow-through electrode. Under optimum conditions, the response was rectilinear from 10 µM to 1 mM CN- and the coefficient of variation were ~2% with a sampling rate of 20 h-1. Total CN- could be determined in the presence of Zn, Cu(II) and Cd but results were low in the presence of Ni, Co(II) and Fe(III). Sulfide and SCN- were not tolerated. The reproducibility was worse than that of spectrophotometric detection but the method could be used over a wider concentration. range and was more suitable for an online control monitoring system.
Cyanide Cyanide, complexes, metal Electrode Electrode Potentiometry

"In-situ Ethanol Probe Based On Sample Dilution In A Double Membrane System"
Anal. Chim. Acta 1988 Volume 215, Issue 1 Pages 71-77
Carl Fredrik Mandenius

Abstract: An in-situ probe suitable for monitoring ethanol in fermenters or other bioreactors is described. It is constructed with an ethanol-permeable double membrane covering a solid-state tin(IV) oxide sensor for gas detection. A stream of nitrogen is passed between the two membranes in order to dilute the ethanol vapor from the fermenter that has passed through the first membrane, before it reaches the second membrane covering the detector. A 100-fold dilution was obtained at a flow rate of 30 mL min-1 of the diluent gas. The delay time was less than 5 min to obtain 80% of maximum response.
Ethanol Fermentation broth Biotechnology Conductometry Electrode

"Simultaneous Determination Of Carbon Dioxide And Sulfur Dioxide In Wine By Gas Diffusion - Flow Injection Analysis"
Anal. Chim. Acta 1989 Volume 225, Issue 2 Pages 443-448
P. Linares, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: The analytes were separated from the sample matrix by passage through the PTFE membrane of a gas diffusion cell, trapped by the acceptor stream (H20) and transported to a potentiometric cell containing a glass-calomel electrode for determination of total CO2 plus SO2. The stream was then merged with a p-rosaniline - formaldehyde solution in 0.7 M H2SO4, and a colored compound was produced by SO2 only, which was determined at 578 nm; CO2 was determined by difference. Mixtures of CO2 and SO2 could be analyzed with an average error of 3.9 and 5.9%, respectively. The reproducibility was 7% and the sampling frequency was ~25 h-1. The method was applied to the simultaneous determination of CO2 and SO2 in wine and was as effective as the standard EEC method, but 8 to 10 times faster, used less sample and reagent and was completely free from interference.
Carbon dioxide Sulfur dioxide Wine Potentiometry Electrode Spectrophotometry

"Flow-through PH-ISFET As Detector In The Determination Of Ammonia"
Anal. Chim. Acta 1990 Volume 231, Issue 1 Pages 53-58
S. Alegret, J. Alonso, J. Bartroli and M. del Valle, N. Jaffrezic-Renault and Y. Duvault-Herrera

Abstract: The alumina pH-ISFET with rear-side contacts described by Van den Vlekkert et al. (Sens. Actuators, 1988, 14, 165) was incorporated in a gas-dialysis flow injection system, which is illustrated schematically. Ammonium ions are converted into NH3, which diffuses through a microporous hydrophobic membrane (Millipore GVHP 0950) into a stream of 2 mM NH4Cl (I adjusted to 4 mM with K2SO4) to form a buffer solution, the pH of which is monitored by the ISFET. The range of rectilinear response was 0.1 to 10 mM, the detection limit was 0.05 mM, and the within-day coefficient of variation (n = 12) at 0.7 mM NH4Cl was 1.03%. The system was applied to river water.
Ammonia River Field effect transistor Electrode Electrode

"Enhancement Of Sensor Selectivity By Gas Diffusion Separation. Part 1. Flow Injection Potentiometric Determination Of Cyanide With A Metallic Silver-wire Electrode"
Anal. Chim. Acta 1990 Volume 233, Issue 1 Pages 77-84
W. Frenzel, C. Y. Liu and J. Oleksy-Frenzel

Abstract: The potentiometric response of a metallic silver-wire electrode in the presence of Ag+-complexing agents was theoretically derived on the basis of the Nernst equation and compared with experimental results. The construction of the silver-wire sensor is described and details are given of its application in gas diffusion flow injection analysis. Microporous polypropylene membranes were used to separate the donor and acceptor channels allowing almost specific determination of CN-. Gaseous interferents, e.g., H2S, SO2 and nitrogen oxides, were chemically converted before entering the gas diffusion unit. The lifetime of the sensor was more than several months. The calibration graph was rectilinear from 10 µM to 10 mM CN-, and concentration. of 0.1 M were measured for long periods without alteration of the response. The continuous corrosion process did not dissolve significant amounts of silver, which was a significant advantage over the common AgI membrane electrodes. The apparent selectivity coefficient obtained were significantly better than those reported for common CN--selective membranes.
Cyanide Potentiometry Electrode Sensor

"Reversible Optosensing In Packed Flow-through Detectors: Flow Injection Or Chromatography?"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 31-40
Jaromir Ruzicka and Gary D. Christian

Abstract: A packed thin-layer detector for reversible flow injection spectrophotometric detection is described. It effectively combines the sensing and reacting media by placing a solid reactive surface in the detection field of a detector. The lifetime of the surface is extended either by protecting it from the sample with a suitable barrier or by renewing the surface before each measurement. The detector was tested in the determination of NH3 by gas diffusion and of PO43- by the molybdenum blue method. The flow injection manifold for the latter is described.
Chromatography

"Flow Injection Analysis For Power Plants: Evaluation Of Detectors For The Determination Of Control Parameters In Conditioned Water-steam Cycles"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 167-173
M. L. Balconi and F. Sigon, M. Borgarello and R. Ferraroli, F. Realini

Abstract: Flow injection methods are presented for the analysis of power plant water. Methods involve various spectrophotometric reagents, gas diffusion, ion-selective and other electrodes, and biamperometry. Analytes include NH3, hydrazine, Cu, Fe and Si, and pH is also measured. Reagents, flow manifolds and detectors are presented for each method. The range of application, coefficient of variation and sampling rate are tabulated for each method, and results are discussed.
Ammonia Hydrazine Copper Iron Silicon pH Water Biamperometry Spectrophotometry Electrode Electrode

"Gas Diffusion Dilution Flow Injection Method For The Determination Of Ethanol In Beverages Without Sample Pretreatment"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 213-220
Wolfgang K&uuml;nnecke and Rolf D. Schmid

Abstract: Sample was injected into water as carrier stream and passed to a gas diffusion unit, in which ethanol passed through a membrane into a stream of 0.1 M phosphate buffer (pH 7.5). This solution was passed through a column containing immobilized alcohol oxidase, and the H2O2 produced was detected at a platinum working electrode at 700 mV vs. Ag - AgCl. The limit of detection was 6 ppm or 0.1 mM ethanol (coefficient of variation 5.2%, n = 15 to 20), and up to 60% ethanol could be determined, depending on the membranes used. The coefficient of variation was generally 0.2 to 0.7%. Up to 180 samples h-1 could be analyzed. The operational half-life of the immobilized enzyme was 8000 injections in 44 h. The method was applied to beer, wine, spirits and pharmaceuticals.
Ethanol Beer Wine Spirit Pharmaceutical Electrode

"Determination Of Total Phosphorus In Waters With Amperometric Detection By Coupling Of Flow Injection Analysis With Continuous Microwave Oven Digestion"
Anal. Chim. Acta 1990 Volume 236, Issue 2 Pages 345-350
S. Hinkamp and G. Schwedt

Abstract: In the manifold (illustrated) of a FIAstar 5020 flow injection analyzer., the sample is injected into a carrier stream of 5 mM H2SO4 (pH 2), which is mixed with 0.06 M HClO4 as decomposing solution before passing through a coil within a microwave oven operated at 650 W. The stream is passed through a gas diffusion unit to remove bubbles before merging with acidic molybdate solution [10 g L-1 of (NH4)6Mo7O24.4H2O and 35 mL L-1 of concentrated H2SO4] and reaction in a coil. The product was reduced to molybdenum blue in an amperometric detector incorporating a vitreous-carbon electrode in wall-jet configuration maintained at +0.26 V vs. Ag - AgCl (3 M KCl). Response based on peak height was rectilinear up to 30 mg L-1 of P, and the detection limit was 0.1 mg L-1 in standard solution The coefficient of variation (n = 5) was 3% at 5 mg L-1 of P. The method gave recoveries ranging from ~63% for pyrophosphate to 91 to 98% for various organic P compounds added to domestic waste water.
Phosphorus Waste Amperometry Electrode Sample preparation

"Utilization Of Adsorption-immobilized Urease In Gas Diffusion Flow Injection"
Anal. Chim. Acta 1990 Volume 237, Issue 2 Pages 503-508
T. L. Spinks and G. E. Pacey

Abstract: The enzyme was immobilized by addition of perfluorialkyl chains to the free amine groups of the enzyme and then adsorption on a PTFE gas-permeable microporous membrane. Injections. of 100 µL of urea were made into a carrier stream of 0.02 M Tris - HCl buffer (pH 8.5) at 0.9 mL min-1. This stream was merged with another stream of the same buffer. When the sample plug reached the membrane there was a 1 min stopped-flow period for conversion of the urea to NH3. The indicator on the acceptor side was Tecator NH3 - N mixed indicator (pH 6.4). When the streams were re-started the change in indicator absorbance was measured at 590 nm. The method was applicable in the range 0.1 to 500 mM urea. The method was used for the determination of urea in whole blood serum, with a sample throughput of 50 samples h-1.
Urea Blood Serum Spectrophotometry

"Flow Injection Determination Of Inorganic Forms Of Nitrogen By Gas Diffusion And Conductimetry"
Anal. Chim. Acta 1991 Volume 245, Issue 2 Pages 183-190
Lourival Cardoso de Faria and Celio Pasquini

Abstract: A flow injection conductimetric method was applied to the determination of ammonia, nitrate and nitrite at concentrations down to 5, 20 and 20 ng mL-1, respectively. Ammonia was determined by merging the injected sample with an alkaline solution (NaOH-EDTA) and passing the mixture through a diffusion cell. The ammonia released was collected by a flowing stream of deionized water that passed through a conductance flow cell. Nitrate and nitrite concentrations were determined after reduction to ammonia in alkaline medium using a column filled with metallic zinc. The ammonia produced was then measured as described above. About 60 samples per hour can be processed with a relative standard deviation of about 1%. Satisfactory agreement was observed between results for ammonia in samples of natural water and nitrate in tap and mineral water determined by the proposed method and by standard spectrophotometric procedures. Speciation can be achieved by adding sulfanilic acid to remove nitrite from the sample and determining the ammonia without the use of the column.
Ammonium Nitrate Nitrite Water Mineral Conductometry

"Monitoring Of Substrates And Products During Fed-batch Penicillin Fermentations On Complex Media"
Anal. Chim. Acta 1991 Volume 249, Issue 1 Pages 123-136
Lars H. Christensen, Jens Nielsen and John Villadsen

Abstract: An automated monitoring system is described (with diagrams) comprising a membrane sampling module for fermentation media, flow injection analysis (FIA) systems for ammonium and glucose determination and exhaust gas analysis system for monitoring O and CO2 and a microcomputer for data acquisition. The O is determined paramagnetically and CO2 determined by IR absorbance. The FIA system for glucose contains a mixing chamber for dilution of the sample and a column of immobilized glucose oxidase. Detection is by chemiluminescence. The RIA system for NH4+ contains a mixing chamber and a gas diffusion device. Cresol red is used as pH indicator and spectrophotometric detection is at 565 nm. The monitoring system was applied to penicillin V fermentation broth.
Penicillin V Glucose Fermentation broth Chemiluminescence Spectrophotometry

"Online Monitoring And Control Of Fermentation Processes By Flow Injection Analysis"
Anal. Chim. Acta 1991 Volume 249, Issue 1 Pages 101-111
Lawrence W. Forman, Benjamin D. Thomas and Fredric S. Jacobson

Abstract: An online tangential-flow filtration device is described (with photographs) for particle-free sampling of fermentation media. The device contains a Durapore 0.2 µm membrane filter disc sandwiched between two stainless-steel plates. The plates have grooves in them which form process flow and filtrate channels. The device was applied in conjunction with flow injection systems for online determination of acetate (I) and phosphate (II) in fermentation media. The I system involved the use of a CO2 stripper and a gas diffusion module and detection of I at 500 nm with phenol red as indicator. The II system involved the reaction of II with molybdic and ascorbic acids and detection at 800 nm. Calibration graphs were rectilinear up to 80 mM I and from 0 to 1 and 1 to 20 mM II. Online flow injection determination of I gave results slightly higher than those obtained by ion chromatography due to the presence of formate. The online flow injection method for II was preferred over an ion-chromatographic method.
Acetate ion Phosphate Fermentation broth Spectrophotometry

"Gas Permeation And Preconcentration In The Flow Injection Determination Of Acid-available Cyanide In Waste Water"
Anal. Chim. Acta 1992 Volume 259, Issue 1 Pages 45-52
Vlastimil Kub&aacute;

Abstract: The optimization of a method involving oxidation of CN- to CNCl and chromogenic reaction with isonicotinate - 3-methyl-1-phenyl-2-pyrazoline-5-one (I) is described, and a flow injection system for application to waste water samples is illustrated. The sample is mixed with 0.1 M H3PO4, and the HCN liberated passes through a silicone rubber membrane in a gas permeation unit into a stream of 25 mM NaOH. This solution is sequentially mixed with 0.1% chloramine T solution in 0.25 M phosphate buffer of pH >8 and with 0.24 M Na isonicotinate - 1 mM I, and the absorbance of the blue final product is measured at 544 nm. Most interference, including that of SCN-, is avoided by the gas permeation technique. With pre-concentration. for 2.5 min in the permeation unit, the detection limit was 3 µg L-1 of CN-. A method for the determination of CN- is based on the reaction with Na isonicotinate-3-methyl-1-phenyl-2-pyrazolin-5-one. A reaction mechanism is proposed. The method allows a fast and sensitive determination.
Cyanide Waste Spectrophotometry

"Simultaneous Flow Injection Analysis For Two Components With Online Dialysis And Gas Diffusion In Series. Determination Of Chloride And Ammonia-nitrogen In Industrial Effluent Water"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 453-459
Jacobus F. van Staden

Abstract: A system is described and illustrated for the simultaneous determination of Cl- and ammonia-N. The sample plug (50 µL) from a single injection, in water as carrier, is routed first to the donor channel of a dialyser, where the Cl- diffuses into H2O; the diffusate is mixed with a reagent containing Hg(SCN)2 and Fe(NO3)3 in aqueous methanolic HNO3 before absorbance measurement at 480 nm. The sample plug is then treated with 0.1 M NaOH and passed to a diffusion unit, where the liberated NH3 passes into an indicator stream containing Tecator NH3 mixed indicator buffered at pH 5.0; the absorbance of the resulting solution is measured at 590 nm. Under optimized conditions, coefficient of variation were 0.8% for Cl- and 1.0% for NH3 in samples containing 127 to 2531 and 10 to 1000 mg L-1 of the respective analytes. The sampling rate was 100 h-1. Online dialysis and gas diffusion were combined for the simultaneous determination of >1 components in a single flow injection analysis system. A fast and reliable fully automated 2-component flow injection procedure is described in which a single sample (e.g., 50 µL of industrial effluent water) is injected into a carrier stream and sequentially dialyzed for the determination of Cl- and gas diffused for the determination of NH3. The results obtained for the Cl- and NH3 in industrial effluent water at a sampling rate of 100/h compared well with those obtained by standard methods.
Chloride Ammonia Industrial Spectrophotometry

"Porous-membrane Permeation Of Halogens And Its Application To The Determination Of Halide Ions And Residual Chlorine By Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 461-469
Shoji Motomizu* and Takehiro Yoden

Abstract: Details are given of a gas diffusion unit (diagram given) with an easily constructed tubular microporous PTFE membrane through which halogen molecules can permeate into an acceptor solution. The sample is introduced via a six-way valve with a variable loop into water as carrier, and this stream is mixed with an oxidizing reagent to generate the molecular halogen (e.g., 10 µM-KMnO4 - 1 M H2SO4 to produce I2 from I-; 0.1 M NaCl - 0.1 M H2SO4 to generate Cl2 from ClO-). After passage through a 10-cm mixing coil, the stream passes through the diffusion unit, where the halogen molecules pass into 0.2 mM NN-diethyl-p-phenylenediamine - 0.1 mM H2SO4 for spectrophotometric detection or (for Cl2) into 0.1 mM acetate buffer of pH 4.8 for potentiometric detection with a coated-wire ion-selective electrode. Conditions are described for the determination of I-, Br-, residual Cl and (by the reduction of I2 to I-, thus affording negative peaks) S2O32-. Microporous polytetrafluoroethylene membrane tubing was used to assemble a newly designed gas diffusion unit and was applied to the permeation of halogens. It was found that halogens such as bromine and iodine, which are not gaseous at room temp., permeated through the membrane tubing; the permeability decreased in the order chlorine > bromine > iodine. The permeated halogens react with N,N-diethyl-p-phenylenediamine to produce colored substances. By coupling this chromogenic reaction with the permeation of halogens, the sensitive and selective determination of halogens and halide ions can be achieved. Iodide and bromide ions were determined by spectrophotometric methods coupled with oxidation by permanganate. Thiosulfate was determined on the basis of the reduction of iodine to iodide. Residual chlorine was determined by a flow injection potentiometric method with a coated-wire ion-selective electrode, and by a flow injection spectrophotometric method.
Halides Chlorine, residual Spectrophotometry Potentiometry Electrode

"Sensitive Flow Injection Technique For The Determination Of Dissolved Organic Carbon In Natural And Waste Waters"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 287-294
R. T. Edwards, I. D. McKelvie*, P. C. Ferrett, B. T. Hart and J. B. Bapat, K. Koshy

Abstract: The sample was injected into water as carrier and treated with 4.2% K2S2O8 solution in aqueous 3.6% NaBH4.10H2O. This mixture was passed through a PTFE coil (4 m x 0.5 mm) wound round a Gelman Clemco 9002 germicidal tube (40 W) for oxidation of the dissolved organic C, and de-bubbled before the introduction of 1 M H2SO4. The stream was then passed through a knotted PTFE coil (70 cm x 0.3 mm) at 95°C to liberate CO2, which, in a gas diffuser, was absorbed in a stream (pH 9.75) of 0.5 mL of methanolic 1% phenolphthalein and 1.5 mL of 0.25 M Na2CO3 - 0.25 M NaHCO3 buffer diluted with water to 1 L. The final solution was de-bubbled before absorbance measurement at 552 nm. Under optimized conditions the detection limit was 0.1 mg L-1 of C and the rectilinear calibration range extended up to 2 mg L-1; slight modification of the manifold extended the upper limit to 80 mg L-1. Recoveries of C from various organic compounds were essentially quantitative. The method was applied to river and estuarine water and to sewage treatment effluent. A flow injection method for the determination of dissolved organic C (DOC) in natural water and wastewater is based on inline UV photooxidation of DOC to CO2, with spectrophotometric detection. The method is rapid (~45 samples/h), has a linear response of 0.1-2.0 mg/L and a detection limit of ~0.1 mg/L. Minor modifications in the manifold can extend the linear response range to 80 mg/L with a slight increase in the detection limit, making the technique well-suited for the determination of DOC in natural water and wastewater.
Carbon, organic, dissolved Estuarine River Water Spectrophotometry

"Determination Of Sulfite In Wine Through Flow Injection Analysis Based On The Suppression Of Luminol Chemiluminescence"
Anal. Chim. Acta 1992 Volume 266, Issue 2 Pages 317-323
Yu Liang Huang*, Jong Min Kim and R. D. Schmid

Abstract: Several flow injection manifolds were tested (diagrams given) for the detection of sulfite in samples in the presence of 1 mM EDTA by the supression effect of sulfite on the reaction between 50 µM-H2O2, 0.5 mM luminol and 4 iu mL-1 of horse-radish peroxidase. The calibration graph was rectilinear from 0.05 to 0.8 mM sulfite (or from 10 to 200 µM-sulfite with 20 µM-H2O2); the coefficient of variation (n = 5) for wine was 4%. A sensitive and rapid assay for total sulfite and SO2 was based on the suppression of luminol chemiluminescence. EDTA greatly amplified this suppression. Flow-through anal. was applied to evaluate the anal. potential for measuring sulfite concentration, with 50 µM H2O2, 0.5 mM luminol, 1 mM EDTA and 4 U/mL horseradish peroxidase being used to induce chemiluminescence. The signal of the suppression of light emission could be obtained within 1 min and was linearly proportional to sulfite concentration. from 10 to 800 µM with a relative standard deviation of <2% over the measurable range. Flow injection analysis with a gas diffusion system based on this principle was applied to measure sulfite concentrations. (free and total) in wine. The results (free and total sulfite concentrations.) can be obtained within 10 min for each wine. The assay was fairly specific for sulfite.
Sulfite Wine Chemiluminescence

"Continuous-flow Method For The Determination Of Total Inorganic Carbonate In Water"
Anal. Chim. Acta 1993 Volume 284, Issue 1 Pages 167-171
Toyoaki Aoki*, Yoshiko Fujimaru, Yuko Oka and Kimiko Fujie

Abstract: Water (5.1 ml/min) was mixed with 0.5 M H2SO4 (1.5 ml/min) and the mixture passed into a membrane separation unit (cf. Anal. Chem., 1983, 55, 1620). The CO2 liberated by acidification permeated through a microporous PTFE tubular membrane (50 cm x 1 mm i.d.) and was collected in a stream of 5 mM NaOH (1.5 ml/min) flowing through an outer PTFE tube (3 mm i.d.). The total inorganic carbonate was determined from the change in electrical conductivity of the NaOH collector stream which was measured using two conductivity detectors; one placed before the membrane separator and one located after it. The calibration graph (relative electrical conductivity vs. concentration) was linear for 0.05-5 mM total inorganic carbonate with a detection limit of 10 µM and RSD (n = 5) of 3.4 and 1.8% at 0.1 and 0.6 mM carbonate, respectively. The response time (98% of steady-state signal) was ~2 min. The effects of various foreign ions were investigated; sulfite interference was prevented by the addition of 0.1 M Cr(VI) to the acid reagent. The method was applied to lake water and the results agreed well with those obtained by nondispersive IR.
Carbonate Lake Conductometry

"Integrated Reduction Method For The Determination Of Urea As Ammonia In Fresh Water Samples"
Anal. Chim. Acta 1993 Volume 284, Issue 2 Pages 249-255
Andre Schmitt, Louise Buttle and Roger Uglow, Kathleen Williams and Stephen Haswell*

Abstract: A flow injection system for the online microwave preparation of water samples with colorimetric determination of urea as ammonia is described. Samples (10 ml) were mixed with 1 mL of reducing agent (20 mL of 96% H2SO4 containing 13.4 g of K2SO4 and 0.2 g of HgSO4, diluted to 100 mL with H2O) and portions (0.8 ml) were injected into a stream (4 ml/min) of water and carried to a 30 m reaction coil mounted in a microwave oven operated at 485 W, where urea was reduced to ammonium ions. After passage through a 7 m cooling coil, the samples were mixed with a stream (1 ml/min) of 1.5 M NaOH in a 12 cm mixing coil and the ammonia produced passed through a gas diffusion cell with a PTFE membrane, causing a pH change in an indicator stream (1 ml/min) of bromothymol blue (0.3 g/l) for detection at 635 nm. The calibration graph was linear from 5-45 µM-urea and the RSD (n = 10) for 40 µM-urea was 3.53%; the detection limit was 2.4 µM. The recoveries were 101% and 95% for 40 and 20 µM-urea, respectively. The sample throughput time was 14 min.
Urea Ammonia Environmental Spectrophotometry

"Direct Determination Of Ammonium In Solid Samples By Automatic Flow Procedures"
Anal. Chim. Acta 1994 Volume 293, Issue 1-2 Pages 163-170
Zheng-liang Zhi, Angel R&iacute;os and Miguel Valc&aacute;rcel*

Abstract: Two manifolds (A and B) are described. For A, the solid sample was suspended in 2.5 M-NaOH, transferred to the flow system and heated to 100°C in air. The released NH3 was collected in 1.5 mL of 2% boric acid. At the end of the extraction period, the boric acid solution was injected into a 2% boric acid carrier stream (1.2 ml/min) which was merged with a Nessler's reagent stream (0.4 ml/min). The absorbance was measured at 400 nm. The calibration graph was linear for 0.4-10 µg/ml ammonium-nitrogen. The RSD (n = 10) for 1 and 3 µg/ml ammonium-nitrogen were 4.9 and 3.3%, respectively. Recoveries of 6 µM-ammonium-nitrogen were 95-105%. The method was applied to soil (details given). For B, a flow-through gas diffusion probe was inserted into the 0.32 M NaOH suspension. The flow of acceptor stream (2% boric acid) through the probe was stopped during the collection period. At the end of the collection period, the acceptor stream (0.8 ml/min) was merged with a Nessler's reagent stream (0.4 ml/min) and the absorbance at 400 nm was measured. The calibration graph was linear for 0.5-10 µg/ml and the RSD (n = 10) for 3 µg/ml ammonium-nitrogen was 4.3%.
Ammonium Environmental Spectrophotometry

"A Fast, Highly Efficient, Continuous Degassing Device And Its Application To Oxygen Removal In Flow Injection Analysis With Amperometric Detection"
Anal. Chim. Acta 1994 Volume 298, Issue 3 Pages 393-399
Jairo J. Pedrotti, L&uacute;cio Angnes and Ivano G. R. Gutz

Abstract: A new continuous degassing device, based on the permeation of gases dissolved in a liquid through the walls of a narrow-bore polymeric tube, is described. The key innovation, responsible for the superior efficiency in relation to other designs, consists in maintaining a reduced pressure of an inert gas (N2, ~1600 Pascal) in the degassing chamber that contains the coiled polymeric tube wandered by the solution. When applied to the continuous removal of oxygen from an electrolyte in flow-injection analysis, FIA, with amperometric detection (flow of 1.0 ml/min, 34 s residence time), a decrease of at least 99.97% in the oxygen reduction current is experienced. Routine determination of 80 samples per hour of heavy metals like cadmium is afforded with a detection limit of about 10 ppb (1.8 x 10^-12 mol of Cd(II) for 20 µL injections), by using a sessile drop mercury electrode. FIA with pre-concentration followed by voltammetric stripping extends the detection limit to the sub-ppb level, as illustrated by monitoring lead and cadmium in samples of drinking water.
Amperometry

"Flow Analysis With Membrane Separation And Time Based Sampling For Ethanol Determination In Beer And Wine"
Anal. Chim. Acta 1995 Volume 305, Issue 1-3 Pages 241-247
Jochen Mohns and Wolfgang K&uuml;nnecke*

Abstract: The flow analyzer. consisted of a dual-channel peristaltic pump, a gas diffusion unit incorporating a PTFE membrane (channel; 0.5 mm depth x 1.4 mm width x 21 mm length), an enzyme reactor containing 10 mg of alcohol oxidase immobilized on to controlled pore glass beads and an electrochemical detection cell operated at 700 mV. One channel of the pump propelled the acceptor stream (0.1 M potassium phosphate buffer at pH 7.5) through the gas diffusion unit and, after the switching of the appropriate valves, through the enzyme reactor and the detector cell. The other channel of the pump propelled samples and standard solutions through the donor channel of the gas diffusion unit. All flow rates were 1.5 ml/min. The flow of both donor and acceptor solutions was stopped to allow ethanol to diffuse across the PTFE membrane. The accumulated ethanol plug was then carried to the enzyme reactor where it was converted to acetaldehyde and H2O2. H2O2 was detected electrochemically. The thickness and pore size of the PTFE membrane controlled the diffusion of ethanol. With 550, 500 and 400 µm thick membranes, the calibration graphs were linear up to 0.6, 7 and 15% ethanol, respectively. The detection limit was 0.0001% ethanol. The RSD (n = 3) for the analysis of samples within the linear calibration range was 2%. The ethanol content of beer and wine samples were determined without sample pretreatment apart from manual degassing. The sampling frequency was 30 samples/h.
Ethanol Beer Wine Amperometry

"Efficiency And Response Studies On Gas Diffusion Manifolds In Flow Injection Systems"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 206-213
Robert Tryzell and Bo Karlberg*

Abstract: The gas transfer efficiency of gas diffusion units fitted with three different types of membranes were compared for the determination of ammonia nitrogen by FIA. The three membranes studied were standard PTFE tape (thickness 0.08 mm), Millipore (0.45 µm) and Celgard 2400 (an effective pore size of 0.05 µm). The FIA manifold allowed the donor stream to be merged with an alkaline reagent. The acceptor stream was 0.1 M HCl and an indicator solution containing bromocresol purple, bromothymol blue and cresol red (4:2:1) was used. Detection was carried out at 590 nm. PTFE tape exhibited transfer efficiencies of 2-17% at a sampling frequency of 60 samples/h and 2-23% at a sampling frequency of 30 samples/h. Millipore and Celgard gave about 80 and 30% of the efficiency and response, respectively, obtained with PTFE tape. The peak height response was dependent on injection volume, groove length in the gas diffusion cell, NaOH concentration and membrane type. The peak height response could be increased by placing the manifold in a ultrasonic bath. The response may be changed by as much as 19% by variations in the installation procedure used to assemble the gas diffusion cell.
Ammonia, nitrogen Spectrophotometry

"Evaluation Of Flow Injection Methods For Ammonium Determination In Waste Water Samples"
Anal. Chim. Acta 1995 Volume 311, Issue 2 Pages 165-173
A. Cerd&agrave;, M. T. Oms, R. Forteza and V. Cerd&agrave;*

Abstract: Five flow injection methods, namely (i) the Berthelot reaction adapted to FIA, (ii) the Berthelot reaction in combination with gas diffusion separation, (iii) the salicylate modification of the Berthelot reaction, (iv) an acid-base spectrophotometric method with gas diffusion separation and (v) gas diffusion separation with conductivity detection, were compared for the determination of ammonia in waste water. The linear range, detection limit and reproducibility of each method were measured. All methods produced a detection limit (0.03-1 mg/l) which was satisfactory for the determination of ammonia in waste water. Interferences were eliminated by using gas diffusion separation. Gas diffusion methods coupled with spectrophotometric or conductometric detection were found to have good precision and sensitivity and were reliable alternatives to the Berthelot methods. The conductivity method had the added advantage of requiring only one reagent (NaOH). Methods based on the Berthelot reaction required a reaction temperature of 60°C which made them unsuitable for in situ applications. All five method were applied to the analysis of waste water samples containing 5-60 mg/l ammonia and the results were compared.
Ammonium Waste Conductometry Spectrophotometry

"Online Flow Injection Monitoring Of Ammonia In Industrial Liquid Effluents"
Anal. Chim. Acta 1995 Volume 314, Issue 1-2 Pages 33-43
Kevin N. Andrewa, Paul J. Worsfolda,* and Michael Comberb

Abstract: A portable, automated flow injection monitor was developed for the online determination of NH3 in industrial liquid effluent streams. The monitor was based on the diffusion of gaseous NH3 from an alkaline sample stream through a PTFE membrane into a bromothymol blue indicator stream and the photometric measurement of the resulting color change using a red LED (λmax = 635 nm). The effluent stream (1.3 ml/min) was mixed with a 0.01 M NaOH stream (1.3 ml/min) and a 20 µL volume of the mixture was injected into a water carrier stream (1.2 ml/min) and passed through the gas diffusion cell. The gas diffusion cell was equipped with a PTFE membrane (thickness 8-9 µm, 24 cm x 15 mm) and had a volume of 72 µL on either side of the membrane. I diffused through the membrane into a 0.1 g/l bromothymol blue stream (1.4 ml/min) and was carried to the detection cell. Calibration was carried out using two standard solution containing 2 and 80 mg/l NH3-N. The calibration graph was linear from 1-100 mg/l NH3-N and the detection limit was 0.6 mg/l. RSD (n = 10) were 3.4 and 0.7%, respectively, for the determination of 2 and 80 mg/l NH3-N. The performance of the monitor was evaluated at two industrial sites and the results were confirmed by an indophenol blue laboratory reference method.
Ammonia Industrial Spectrophotometry

"Analysis Of Ammonia And Methylamines In Natural-waters By Flow Injection Gas Diffusion Coupled To Ion Chromatography"
Anal. Chim. Acta 1995 Volume 316, Issue 3 Pages 291-304
Stuart W. Gibb, R. Fauzi C. Mantoura and Peter S. Liss

Abstract: Flow injection gas diffusion-ion chromatography (FIGD-IC), is a new hyphenated technique for the simultaneous analysis of nanomolar levels of ammonia (NH3) and methylamines (MAs) in < 50 mi of marine, estuarine and freshwaters. Alkaline EDTA is added online to flowing sample to achieve a sufficiently high pH (> 12.0) needed to deprotonate > 95% of the amines to their uncharged volatile forms. In addition the reagent chelates Mg2+ and Ca2+ to prevent their precipitation as Ca(OH)(2) and Mg(OH)(2). The amines diffuse selectively across a gas-permeable microporous PTFE Goretex(R) membrane into a recirculating flow of acidic 'acceptor' in which they are reprotonated and pre-concentrated. The acceptor solution is then injected onto an ion chromatograph (IC) where NH4+ and MA cations are separated within 15 min and detected by chemically suppressed conductimetry using cyclopropylamine as an internal standard for quantification. The response of the coupled FIGD-IC system was sensitive (ca. 3-5 nM for MAs, 20-40 nM for NH3), linear (r2 = 0.99, 0-2000 nM in seawater) and precise (RSD = 1-6% at 1 µM) for all analytes. The applicability of FIGD-IC is demonstrated through laboratory analysis of NH3 and MAs in a range of natural water samples, on-board a research vessel, and through inter-comparisons with fluorimetric assay of NH3. (40 References)
Amines, methyl Ammonia Environmental Estuarine Sea HPIC Conductometry

"Sequential Analyte Removal In Flow-analysis Determination Of Nitrogen, Phosphorus And Potassium In Fertilizers"
Anal. Chim. Acta 1995 Volume 317, Issue 1-3 Pages 239-245
Patricia Benedini Martellia, Jos&eacute;Anchieta Gomes Netoa, Elias Ayres G. Zagattoa,*, Sandra M. Boscolo Brienzab, M. Concei&ccedil;&atilde;o B. S. M. Montenegrob and Jos&eacute;Luis F. Costa Limab

Abstract: A new approach for multiparametric determinations in now analysis based on successive sequestering of analytes is proposed and exemplified in the determination of water soluble nitrogen, phosphorus and potassium in fertilizers. The analytes are partially and reproducibly removed from the sample zone in the main stream towards specific analytical channels without significant alterations in the flowing sample plug. By using gas diffusion, dialysis and asymmetric stream splitting, ammonium, potassium and orthophosphate ions are stripped out and determined by flow potentiometry, flame photometry and spectrophotometry, respectively. The system permits up to 75 samples to be examined per hour, requires 90 mg tris(hydroxymethyl)aminomethane plus 75 mg ammonium heptamolybdate tetrahydrate plus 75 mg ascorbic acid per sample, and yields reproducible results (RSD usually < 3%) in agreement with usual manual procedures. The feasibility of an analogous modular system with a random selection of procedures is discussed. (17 References)
Nitrogen Phosphorus Potassium Commercial product Spectrophotometry Spectrophotometry Potentiometry

"Gas Diffusion Techniques Coupled Sequential Injection Analysis For Selective Determination Of Ammonium"
Anal. Chim. Acta 1996 Volume 318, Issue 3 Pages 251-260
M. T. Oms, A. Cerd&agrave;, A. Cladera, V. Cerd&agrave;* and R. Forteza

Abstract: A computer-controlled sequential injection analysis system for the determination of ammonium ions in water is described. A 75 µL sample and 100 µL 0.01 M NaOH were sequentially aspirated and mixed by flow reversal while being propelled (2 ml/min) to a gas diffusion unit. Ammonia diffused through a Durapore hydrophobic membrane (0.22-0.45 µm pore size, 125 µm thick) and was collected in 1 mL 80 µM-bromothymol blue (BTB) at pH 6. The BTB was propelled to a spectrophotometer and the absorbance was measured at 620 nm. The calibration graph for ammonium ions was linear for up to 60 mg/l and the RSD (n = 10) at 30 mg/l was 2.5%. The detection limits were 2 and 0.5 mg/l for one and five flow reversals, respectively. No interference from a 20-fold excess of Cu(II), Fe(III) and Zn, a 40-fold excess of carbonate or sulfite, Ca and Mg or a 100-fold excess of chloride, nitrate or sulfate was observed. The method was applied to the analysis of filtered waste water and aqueous extracts of atmospheric aerosols. The results were confirmed by a FIA method based on the formation of indophenol blue.
Ammonium Waste Environmental Spectrophotometry

"Online Multicomponent Determination Of Organic Compounds In Water Following Gel-permeation Chromatographic Separation"
Anal. Chim. Acta 1996 Volume 319, Issue 1-2 Pages 165-175
Jolanta Oleksy-Frenzel* and Martin Jekel

Abstract: A system coupling GPC with air-segmented flow analyzer.s for dissolved organic carbon (DOC), nitrogen (DON) and halogens (DOX) was described for the characterization of water samples. The chromatography was carried out on a Fractogel TSK 40 HW column (70 cm x 16 mm i.d.) with a sample injection volume of 1 ml, phosphate buffer at pH 7 as the mobile phase (0.8 ml/min) and UV-visible diode array detection (190-800 nm). The column effluent was divided into two streams. One steam passed to the DOC analyzer. and the other to the DON analyzer. and then to the DOX analyzer.. The DOC analyzer. was based on the H2SO4 oxidation of organic carbons to CO2 which was collected via a gas diffusion unit and detected photometrically with a pH indicator. The DON analyzer. was based on the oxidation of organic nitrogen to nitrate by UV digestion in the presence of peroxodisulfate for spectrophotometric detection. The DOX analyzer. was based on the potentiometric detection of halides at a Ag/AgCl electrode. The system was tested with various organic compounds and quantitative recoveries were obtained. The system was applied to the characterization of filtered waste water from chemical processing.
Organic compounds Environmental Waste GPC Potentiometry Spectrophotometry Sample preparation

"Determination Of Trimethylamine In Fish By Flow Injection Analysis"
Anal. Chim. Acta 1996 Volume 321, Issue 1 Pages 69-74
Saloua Sadok, Roger F. Uglow and Stephen J. Haswell*

Abstract: In the FIA method described for the determination of trimethylamine (I) in fish muscle extracts, a 1 g portion of tissue was homogenized with 3 mL of HClO4. The homogenate was centrifuged at 24 000 g for 30 min at 4°C, and 100 µL portions of the supernatant were injected into a carrier stream (1 ml/min) of aqueous 12% formaldehyde. This stream merged with 0.6 M NaOH (1 ml/min) and the mixture was propelled to a gas diffusion cell (channel dimensions 24 cm x 1.5 mm x 0.2 mm) fitted with a PTFE membrane. The I diffused through the membrane, and was collected in a stream of 0.03% bromothymol blue solution (1 ml/min) and transported to a laboratory-built detector fitted with red light-emitting diodes. A linear calibration graph was obtained for up to 200 µM-I and the detection limit was 6 µM. The RSD (n = 10) for 1.31 µg/g of I in wet tissue was 1.5%. The recoveries of 50 µM-I added to fish extracts were quantitative.
Trimethylamine Marine Spectrophotometry Sample preparation

"Flow Injection Analysis With Chemiluminescent Detection Of Sulfite Using Sodium Carbonate-sodium Bicarbonate-copper Ion System"
Anal. Chim. Acta 1996 Volume 323, Issue 1-3 Pages 69-74
Jin-Ming Lin* and Toshiyuki Hobo

Abstract: An FIA system incorporating a gas diffusion cell is described for the selective determination of sulfite. A 100 µL sample was injected into a 0.1 M H2SO4 stream (0.5 ml/min) and transported to the cell, where the liberated SO2 diffused through a PTFE membrane (0.02 µm pore size, 45 µm thickness) and was collected in a 0.6 M Na2CO3 stream (0.5 ml/min). The collector stream was propelled to the chemiluminescence detector and mixed with a reagent stream formed by merging 0.4 M NaHCO3 and 0.5 mM Cu(II) (both at 1.5 ml/min). The light emitted was detected by a photomultiplier tube. The calibration graph obtained by plotting light intensity vs. log. sulfite concentration was linear for 1 µM-0.5 mM, the detection limit was 0.5 µM, and the RSD (n = 9) for 5 µM-sulfite was 4.6%. The method was applied to the determination of sulfite in wine following 100-500-fold dilution. The results were verified by a titration method with iodine.
Sulfite Wine Chemiluminescence

"Selective Determination Of Gas Dialysable Components In Complex Sample Solutions Using Triangle Programmed Coulometric Titration In Continuous-flow Systems"
Anal. Chim. Acta 1996 Volume 324, Issue 2-3 Pages 115-123
M. Becker, B. Fuhrmann and U. Spohn*

Abstract: A method is described for determining ammonium/NH3 and sulfide/hydrogen sulfide in leachate from a municipal waste land-fill site. Sample (0.1 ml/min) was merged with a conditioning stream (0.1 ml/min) of 0.1 M NaOH (for ammonium/NH3) or 0.1 M HCl (for sulfide/hydrogen sulfide) and the mixture was propelled through the donor channel of a dialysis cell. The generated NH3 and H2S were adsorbed into acceptor streams (0.2 ml/min) of 0.1 M KBr/0.1 M sodium borate of pH 8.3 or 0.1 M KBr/0.1 M NaHCO3, respectively, and titrated with electrogenerated hypobromite produced at Pt electrodes by the oxidation of bromide. After the oxidations of NH3 and H2S, the remaining bromine was detected amperometrically at a Pt electrode (0.18 V) and the remaining hypobromite was detected by chemiluminescence via its reaction with 20 µM-luminol (2 ml/min). For ammonium/NH3, the linear ranges were 10 µM-10 mM with amperometric detection and 1 µM-0.5 mM with chemiluminescence detection and RSD (n = 6) were 3%. The linear range for sulfide/H2S was 0.2 µM-0.5 mM with chemiluminescence detection and the RSD (n = 6) was 4%. The sampling frequency was 30 samples/h.
Ammonium Sulfide Waste Coulometry Amperometry Electrode Chemiluminescence

"Automated Analytical Biosystem For Urea Monitoring"
Anal. Chim. Acta 1996 Volume 327, Issue 3 Pages 243-251
M. Jurkiewicz, M. Del Valle, S. Alegret and E. Mart&iacute;nez-F&aacute;bregas*

Abstract: Sample was injected into a carrier stream of 0.1 M Tris buffer of pH 7.4. The stream flowed through a nylon column onto which urease was previously immobilized. The carrier stream containing the hydrolyzed ammonium ions was then merged with a stream of 1 M NaOH and passed through a reaction tube. The resulting NH3 gas was transported to a gas diffusion cell in which NH3 gas diffused through a hydrophobic membrane into another carrier solution of 0.1 M Tris buffer for measurement by an ammonium ISE. Measurements were made relative to a Ag/AgCl reference electrode. Under optimum conditions, calibration graphs were linear for 30 µM to 3 mM. For hemodialysis measurements, the experimental parameters had to be adjusted; under such conditions the response was linear only for 1-2 mM.
Urea Potentiometry Electrode

"Determination Of Arsenic By Hydride-generation Gas Diffusion Flow Injection Analysis With Electrochemical Detection"
Anal. Chim. Acta 1996 Volume 334, Issue 1-2 Pages 193-197
J. R. Farrell, P. J. Iles,* and Y. J. Yuan

Abstract: A 300 µL sample of As2O3 in 8% (v/v) HCl was injected into 8% (v/v) HCl that had been premixed with 0.2% (w/v) NaBH4 solution in 0.01 M NaOH. AsH3 generated in the donor stream (1 ml/min) diffused through the PTFE membrane of a gas diffusion cell (described) into 0.5 mM Br2 pumped (1 ml/min) through the upper chamber that was fitted with a flow-through conductometric detector. Calibration graphs were linear for 2.5-50 mg/l of As, with detection limits of 2 and 0.2 mg/l for flow rates of 1 and 0.3 ml/min, respectively. The RSD (n = 6) was 4.6% at 10 ml/min. Alternatively, AsH3 generated with 0.5% (w/v) NaBH4 solution in 0.01 M NaOH (1 ml/min) was trapped in 0.01 M H2SO4 (1 ml/min) and determined in a thin-layer flow-through amperometric cell with a dual Au working electrode and an Ag/AgCl reference electrode. Calibration graphs for 0.01-1 mg/l of As and 0.5-40 mg/l As were non-linear. The detection limit was 0.01 mg/l and the RSD (n = 6) were 3.4 and 4% for 1 and 0.1 mg/l of As, respectively.
Arsenic Amperometry Conductometry

"Study Of Equilibria In Cyanide Systems By Gas Diffusion Measurement Of Hydrogen Cyanide"
Anal. Chim. Acta 1996 Volume 336, Issue 1-3 Pages 131-140
Jamal A. Sweileh

Abstract: Speciation of hydrogen cyanide in different metal-cyanide systems at the µg mL-1 level was established by the selective measurement of hydrogen cyanide (HCN) diffused through a microporous Teflon membrane under thermodynamic equilibrium conditions. The test solution was continuously aspirated through the donor side of the gas diffusion unit until equilibrium was achieved with the stagnant buffer solution on the receptor side. The final assay of HCN was carried out spectrophotometrically (chloramine-T/barbiturate/isonicotinate) in the flow injection mode. The theoretical relation between the enrichment factor and the pH of the donor and receptor solutions was derived and experimentally verified. As confirmed by calculation the speciation of HCN can be established for simple soluble cyanides and cyanide complexes with log formation constants as high as 20. For more stable cyanide complexes the results are satisfactory; but for the highly stable hexacyanoferrate(III) this method is not feasible. The speciation of cyanide in metal-cyanide systems was studied by measuring the HCN concentration using a gas diffusion cell incorporated into a flow injection spectrophotometric system. The metal-cyanide test solution was pumped (2 ml/min) through the donor channel of the gas diffusion cell for 6 min until equilibrium was reached. During this period the acceptor solution, 0.1 M NaH2PO4 of pH 7, was kept stationary. At the end of the sampling period, the acceptor solution was injected into a carrier stream (0.4 ml/min) of 0.1 M NaH2PO4 of pH 7 and merged with 0.01% chloramine-T (0.4 ml/min) and sodium barbiturate/sodium isonicotinate reagent (1.6 ml/min). The mixture was heated to 68°C and propelled to the detection cell where the absorbance was monitored at 600 nm. The acceptor and donor channels of the gas diffusion cell had volumes of 0.108 mL. The apparatus was calibrated with 0.1-1 µg/ml NaCN. The calibration graph was linear, the detection liwas 0.025 ng/ml and the RSD (n = 9) for 0.5 µg/ml cyanide was 0.6%. The method was applied to metal-cyanide complexes at various pH values from 2-11. At each pH the concentration of each species was calculated using two mass balance equations, one for total cyanide and the other for total metal. 19 References
Hydrogen cyanide Spectrophotometry

"Determination Of L-asparagine Using Flow Injection Systems With Spectrophotometric And Potentiometric Detection"
Anal. Chim. Acta 1996 Volume 336, Issue 1-3 Pages 113-122
Kathrin Stein*, Renbing Shi and Georg Schwedt

Abstract: Two FIA methods were developed for determining asparagine in foods. The first method was based on the catalyzed hydrolysis of asparagine by immobilized asparaginase to yield NH3. The NH3 diffused through a PTFE membrane and was detected (i) spectrophotometrically using an acid-base indicator solution as the acceptor or (ii) potentiometrically using a pH electrode and water as the acceptor. The linear ranges and RSD (n = 5) were 0.2-2.3 mM and 1.7% (at 0.75 mM asparagine), respectively, for spectrophotometric detection and 0.1-4 mM and 2.5% (at 1 mM asparagine), respectively, for potentiometric detection. The sampling frequency was 35/h. The second method used a biosensor fabricated by attaching a membrane with immobilized asparaginase on to a pH electrode. The linear range and RSD (n = 5) of this method were 0.1-2 mM and 2.3% (at 1 mM asparagine), respectively. The sampling frequency was 30/h. The methods were applied to apple and orange juice, oranges and asparagus. The sample preparation procedure involved diluting the fruit juices or filtering the homogenates of the solid foods. Recoveries of 50 mg/l or 50 mg/100 g asparagine from spiked foods were >94.3%.
l-asparagine Food Fruit Juice Juice Fruit Vegetable Potentiometry Electrode Spectrophotometry Sensor

"Determination Of Sulfite In Wines By Gas Diffusion Flow Injection Analysis Utilizing Spectrophotometric PH-detection"
Anal. Chim. Acta 1997 Volume 337, Issue 2 Pages 125-131
L. G. Decnop-Weever* and J. C. Kraak

Abstract: A flow injection spectrophotometric method was developed for determining total sulfite in wines. The sample preparation procedure was carried out in a N2 atmosphere using a solution that had been degassed with N2. A wine sample of 25 mL was mixed with 50 mL of 10% ethanol and then 10 mL 2.5 M KOH was added. After 5 min, the following solutions were added in succession; 6.25 mL 2 M H2SO4 in 10% ethanol, 25 mL 2 M H2SO4 in 10% ethanol and sufficient 10% ethanol to give a total volume of 250 mL. A 40 µL portion of the resulting solution was immediately injected into a carrier stream (0.9 ml/min) of 1 M H2SO4 in 10% ethanol and passed through the donor channel of the gas diffusion cell. The SO2 diffused through the PTFE membrane and was collected in the acceptor stream (0.9 ml/min), 35 mg/l bromocresol green in 10% ethanol at pH 5.5. The absorbance of the acceptor stream was monitored at 620 nm. The method was calibrated for 1-20 mg/l sulfite and the detection limit was 0.1 mg/l. The method was applied to white, red and rose wines. The RSD (n = 6) for the peak heights was 0.7-1.5%. The recoveries of up to 7.5 mg/l sulfite from spiked wines were 96-109%. The sampling frequency was 120/h.
Sulfite Wine Sample preparation Spectrophotometry

"Calibration Methods For Determination Of Ammonium And Excess Acid In Kjeldahl Digests By Flow Injection Analysis"
Anal. Chim. Acta 1997 Volume 343, Issue 3 Pages 183-190
Robert Tryzell and Bo Karlberg*,*

Abstract: Calibration methods were evaluated for determining ammonium in Kjeldahl digests by flow injection spectrophotometry. The FIA method was based on the separation of gaseous NH3 from a NaOH carrier stream using a gas diffusion unit fitted with a Celgard 2400 membrane. The NH3 was collected in an indicator mixture of bromcresol purple/bromthymol blue/cresol red and the absorbance was measured at 590 nm. The Kjeldahl digests were prepared digesting a 1 g sample with 7 g K2SO4, 0.8 g CuSO4.5H2O and 12 mL H2SO4 for 1 h at 420°C. Univariate calibration based on peak areas allowed accurate and precise determination of ammonium when the injection volume was small, viz., Calibration by partial least squares using the entire response curve (1098 data points) allowed both the ammonium and the excess acid to be determined from a single sample injection. Calibration standards containing five concentration levels of ammonium (40, 100, 200, 300 and 400 ppm) and six levels of H2SO4 (0, 0.105, 0.248, 0.330, 0.413 and 0.495 mol/l) were used. The lowest root mean square error of prediction ( The PLS calibration method was used to determine the protein content of feed.
Protein Ammonium Acids Feed Spectrophotometry

"A Novel Gas Diffusion/flow Injection System Coupled With A Bulk Acoustic-wave Impedance Sensor For Total Inorganic Carbonate And Its Application To Determination Of Total Inorganic And Total Organic-carbon In Waters"
Anal. Chim. Acta 1997 Volume 349, Issue 1-3 Pages 143-151
Xiao-li Su, Li-hua Nie and Shou-zhuo Yao*

Abstract: A novel flow injection analysis (FIA) system has been developed for the rapid and selective determination of total inorganic carbonate (TIC). The method is based on the diffusion of CO2 across a PTFE gas-permeable membrane from a stream of 0.5 mol L-1 H2SO4 (0.50 mL min-1) and water (0.50 mL min-1) merging into a stream of 10 mM tris(hydroxymethylamino)-methane containing 0.5 mM KCl (1.00 min min-1). The CO2 trapped in the acceptor solution is determined online by a bulk acoustic wave impedance sensor and the signal is proportional to the concentration of TIC present in the original samples. The proposed system was applied to the direct determination of TIC in natural and waste waters and the indirect determination of the total organic carbon content based on wet chemical oxidation of the samples, it exhibited a linear frequency response up to 20 mM bicarbonate with a detection limit of 10 µM, and the precision was better than 1% (RSD) at a throughput of 45 samples per hour. The effects of composition of acceptor stream, cell constant of the conductivity sensor, sample volume, flow rates and potential interferents on the FIA signals were discussed in detail. 32 References
Carbon, organic, total Carbon, inorganic, total Environmental Waste Sensor

"Turbidimetric Flow Injection Determination Of Total Nitrogen And Potassium In Vegetables"
Anal. Chim. Acta 1997 Volume 356, Issue 2-3 Pages 259-265
Jos&eacute; L. F. C. Limaa, Ant&oacute;nio O. S. S. Rangelb,*, M. Renata S. Soutob and Elias A. G. Zagattoc

Abstract: A turbidimetric flow injection system was developed for the determination of total nitrogen and potassium in vegetable samples using a single spectrophotometer as detector. As a precipitating agent, 3.0% (w/v) sodium tetraphenylboron solution prepared in 2.0% (w/v) poly(vinyl alcohol) was used. A gas diffusion process was included in the manifold to separate ammonium ions from the rest of the sample and to allow paired analysis. Total nitrogen and potassium determinations were carried out on the solutions remaining in the acceptor and donor streams, respectively. Results obtained were precise (relative standard deviations <2.1 and 1.6% for total N (<25 mg g-1) and K (<55 mg g-1) determinations, respectively) and in agreement with those of reference methods. Analysis can be carried out at a rate of up to 35 samples per hour (corresponding to 70 determinations per hour) within concentration range 87-430 mg N-NH4+ L-1 and 78-390 mg K+ L-1 for the total nitrogen and potassium determinations, respectively. 17 References
Nitrogen, total Potassium Vegetable Turbidimetry

"Flow Injection Conductimetric Or Spectrophotometric Analysis For Acidity In Fruit Juice"
Anal. Chim. Acta 1998 Volume 363, Issue 2-3 Pages 199-202
Kate Grudpan*, Piyanete Sritharathikhun and Jaroon Jakmunee

Abstract: Two flow injection (FI) procedures for the determination of acidity (expressed as citric acid content) in fruit juices are proposed: conductimetric involving injection into ammonia followed by gaseous diffusion into acetic acid; spectrophotometric FI titration in which the sample is mixed with sodium hydroxide in the presence of phenolphthalein. These procedures have been applied to the anal. of Thai fruit juices having acidity at a level of about 1% (wt./v) citric acid. The relative standard deviations (n=12) were within the ranges 3.6-6.2% and 0.7-2.2%, respectively, for the conductimetric and spectrophotometric procedures, the latter showing a negative bias due to the presence of colored matter in the samples. Sodium chloride and sucrose, when present in concentrations of up to 2% and 10% (wt./v) respectively, do not interfere. Results obtained by either procedures are consistent with those obtained by a standard classical titrimetric method.
Acidity, total Fruit Conductometry Spectrophotometry

"Comparison Of Various Peak Evaluation Techniques For Limited And Extended Dynamic Ranges In Flow Injection Systems"
Anal. Chim. Acta 1998 Volume 364, Issue 1-3 Pages 97-106
Robert Tryzell and Bo Karlberg*

Abstract: Various peak evaluation and calibration techniques were compared for two-line and gas-diffusion FIA systems, designed for the determination of Fe(II) and ammonium, respectively. The univariate peak evaluation techniques comprised of peak height, peak area, peak width, slope value at the 1st inflection point and triangulated peak height and area. All these techniques were utilized to condense each FIA peak to one single value prior to fitting a 2nd order polynomial to the data by regression anal. When multivariate data anal. was performed each peak was represented by a large number of values evenly distributed over the entire FIA peak and partial least squares (PLS) regression was applied. The injected standard solutions covered a large concentration. range, three orders of magnitude for both system types, and a relative viscosity (.eta./.eta.0) range of 1.000-1.128 for the two-line system and 1.000-1.104 for the gas-diffusion system. Triangulated peak area data can replace peak height and peak area for univariate evaluation in the two-line FIA system applied for standards within the limited, linear concentration. range, and become the measure of choice for the extended, nonlinear concentration. range. For the gas-diffusion method the peak height, the peak area, the slope value at the 1st inflection point and the triangulated peak height or area work equally well in the limited concentration. range. For the extended concentration. range the only univariate peak evaluation technique that was found to work satisfactorily was peak area by triangulation. PLS regression provides an alternative, universal solution to the problems with matrix variations and large concentration. ranges but in a given situation it is not always superior to the best of the various univariate approaches. The PLS calibration technique requires a much larger number of standards in comparison with the univariate approaches.
Iron(2+) Ammonium Spectrophotometry

"Determination Of Ammonia In Wastewaters Containing High Concentrations Of Surfactants By Flow Injection Potentiometry With Online Sample Clean-up"
Anal. Chim. Acta 1998 Volume 367, Issue 1-3 Pages 193-199
Hongda Shen, Terence J. Cardwell* and Robert W. Cattrall

Abstract: It was demonstrated that surfactants lead to problems in the anal. of NH3 in gas-diffusion flow injection by wetting the membrane to allow transport of potentially interfering species to the detector. An online clean-up procedure, using an activated C cartridge to remove ionic and non-ionic surfactants (≤1000 mg/L) and other organic compounds from aqueous samples, is described. Ammoniacal nitrogen was determined in synthetic samples by gas-diffusion flow injection with a nonactin-based potentiometric sensor used as an NH4+ ion detector. Analyses were performed at a sampling rate of ~25/h; the cartridge was effective for at least 1000 injections of 50 µL samples at 1-180 mg/L concentrations The procedure was used to analyze wastewater; it was efficient in removing ionic and non-ionic surfactants from acidified (pH 1) samples.
Ammonia Waste Potentiometry Electrode

"Comparison Of Photometry And Conductometry For The Determination Of Total Carbonate By Gas Permeation Flow Injection Analysis"
Talanta 1993 Volume 40, Issue 6 Pages 831-840
Vlastimil Kub&aacute; and Purnendu K. Dasgupta*,

Abstract: A manifold for the flow injection determination of total carbonate (i.e, dissolved CO2) in acidified sample solution is described (diagram given). Sample solution was mixed with 0.5 M phosphoric acid modifier/conditioning reagent and the mixture was pumped through a tubular Si membrane permeation device (120 mm x 0.4 mm), which allowed the pre-concentration. of CO2 in a suitable receptor solution before its photometric or conductometric determination. For the photometric determination the receptor solution was 50 µM-cresol red in carbonate/bicarbonate buffer (pH 9) and the change in absorbance at 434 nm was measured. The best receptor solution for the conductometric determination was 1-10 mM tris(hydroxymethylamino)methane. Interference from sulfite and sulfide was eliminated using sulfuric acid/potassium permanganate as the modifier/conditioning reagent. To avoid interference from cyanide, a more complex manifold was required to allow oxidation under alkaline conditions before sample acidification. The conductometric method provided better day-to-day reproducibility, sensitivity and detection limits than the photometric method.
Carbonate Spectrophotometry Conductometry

"Indirect Determination Of Tetrahydroborate By Gas Diffusion Flow Injection Analysis With Amperometric Detection"
Talanta 1993 Volume 40, Issue 8 Pages 1283-1287
Sneana D. Nikoli and Emil B. Milosavljevic*, James L. Hendrix and John H. Nelson

Abstract: A solution of BH4- in aqueous 1% NaOH was injected into a carrier stream (2 ml/min) of water, which was mixed with a stream (2 ml/min) of 25 mM As(III) in 1 M HCl in a mixing coil (30 cm x 0.5 mm). The AsH3 formed diffused through the PTFE membrane of a gas diffusion unit into an acceptor solution (0.01 M H2SO4) and the resulting solution passed through the thin-layer flow cell of a BAS LC-17A amperometric detector equipped with dual Pt working electrodes maintained at 0.8 V vs. Ag/AgCl. The calibration graph was linear from 8 µM to 1 mM BH4-, and the detection limit was 1 µM. The RSD at 60 µM was 2% and the sample throughput was 60/h. Serious interference was caused by sulfide and sulfite.
Tetrahydroborate ion Amperometry Electrode

"Reverse Dual Phase Gas Diffusion Flow Injection Analysis"
Talanta 1993 Volume 40, Issue 12 Pages 1961-1966
K. J. Smith and G. E. Pacey

Abstract: For the determination of CO2 in gases, the gas stream (62 ml/min) was passed in front of a Celgard 2500 membrane. On the other side of the membrane, the receptor solution flow was stopped for 15 s, while the CO2 diffused across the membrane. The receptor solution contained 10 mL of 0.1% cresol red in 2 mM NaOH, diluted to 1 l with 1 mM carbonate buffer of pH 8.85 which was pumped at 1.9 ml/min to the detector at 430 nm. The membrane efficiency was 30.6%. The calibration graph was linear for 6.7-197 g/m3 of CO2 with a detection limit of 2 g/m3. Other calibration ranges could be obtained by varying the buffer concentration. A similar method was devised for the determination of hydrazine in air with a gas flow rate of 225 ml/min; the receptor solution containing 0.1 g/l of bromophenol blue adjusted to pH 3.9 with 0.5 M HCl was stopped for 20 min and measurements were made at 460 nm. The membrane efficiency was 17.4%. The calibration graph was linear for 0.035-0.14 ppm of hydrazine with a detection limit of 0.01 ppm. The sensitivity of the membrane decreased slowly over a 6 day period. Interferences by NH3, monomethylhydrazine and 1,1-dimethylhydrazine are discussed.
Carbon dioxide Gas

"Gas Diffusion With Preconcentration For The Determination Of Fluoride In Water Samples By Flow Injection"
Talanta 1994 Volume 41, Issue 1 Pages 115-123
T. J. Cardwell*, R. W. Cattrall and M. Mitri

Abstract: Fluoride-containing solution (0.8 ml/min) and 1.25% hexamethyldisilazane in 1 M H2SO4 (0.8 ml/min) were mixed in a 330 cm coil held at 88-90°C and the trimethylsilane generated was absorbed in a stationary 0.1 M NaOH acceptor stream after diffusion through a gas-permeable fluoropolymer membrane in a gas diffusion module (illustrated). The pre-concentrated sample was flushed with additional 0.1 M NaOH (1.5 ml/min), then mixed with a pre-mixed solution of 2.3 mM alizarin red S (0.6 ml/min) and 1.1 mM zirconyl chloride in 0.2 M H2SO4/0.55 M HCl (0.6 ml/min). The yellow alizarin sulfonate ion, arising from the reaction of zirconium/alizarin sulfonate with fluoride, was measured at 520 nm. The calibration graph was linear for 0.1-4 mg/l of fluoride although the method is suitable for analysis of 0.1-10 mg/l of fluoride with a RSD of ~3% for fluoride concentration 3 mg/l. The detection limit was 0.055 mg/l and the quantification limit was 0.18 mg/l. Phosphate ions did not interfere with toleration levels of Al and Fe at 200 and 500 times the fluoride concentration, respectively.
Fluoride Environmental Spectrophotometry

"Pervaporation: An Integrated Evaporation/gas Diffusion Approach To Analytical Continuous Separation Techniques"
Talanta 1995 Volume 42, Issue 5 Pages 755-763
Ivanildo L. de Mattos*, M. D. Luque de Castro and Miguel Valc&aacute;rcel,

Abstract: A flexible pervaporation module was developed and characterized. The spacers it uses allows the volume of the donor and/or acceptor to be altered as required. The performance of the module was tested as regards both dynamic behavior and continuous pervaporation in terms of flow-rates, temperature, type of membrane, flow mode, etc. A method for the determination of ethanol in different types of wine was developed and applied to various samples in order to validate the proposed continuous separation approach.
Ethanol Wine

"Flow Injection Analysis Chemiluminescence Detection Of Residual Ozone"
Talanta 1995 Volume 42, Issue 8 Pages 1045-1050
K. A. McGowan and G. E. Pacey*,

Abstract: Chemiluminescent reagents for the determination of residual ozone were compared. Each method was automated using gas diffusion flow injection analysis (diagram and description given). The reagents investigated were indigo disulfonate, indigo trisulfonate and luminol. The luminol method offered a much larger working range (48.4-155 µM-ozone) than the other two methods and the detection limit was 0.008 mg O3/l.
Ozone Water Chemiluminescence

"Flow/sequential Injection Determination Of Gaseous Ammonia With A Glass Diffusion Denuder"
Talanta 1995 Volume 42, Issue 10 Pages 1545-1551
Yongyi Luo, Rashed Al-Othman, Gary D. Christian* and Jaromir Ruzicka

Abstract: A schematic diagram of the injection system is presented. The flows were driven by a peristaltic pump and solutions were selected by an eight-port rotary selection valve. Gaseous NH3 was selectively absorbed in a phosphoric acid-coated glass tube and determined with Berthelot reagents by flow injection. Calibration graphs were linear from 0.15-4 µg and the detection limit was 0.15 µg NH3. The method can be applied to the determination of NH3 in air. A new combination of a flow/sequential injection method for the analysis of ammonia has been developed. Gaseous ammonia is selectively absorbed in a phosphoric acid coated glass tube and determined with Berthelot reagents by flow injection. The combination of the gas diffusion denuder sampler with flow injection makes this method very sensitive and selective. The limit of detection of 0.15 µg NH3. (29 References)
Ammonia Environmental Spectrophotometry

"Flow Injection Gas Diffusion Amperometric Determination Of Trace Amounts Of Ammonium Ions With A Cupric Hexacyanoferrate"
Talanta 1996 Volume 43, Issue 7 Pages 1049-1054
Renmin Liu, Bianting Sun, Daojie Liu and Ailing Sun

Abstract: Sample was injected into a carrier stream (4 ml/min) of water which then merged with a reagent stream (1 ml/min) of 0.2 M NaOH containing 0.1 M sodium citrate. The resulting stream and a stream (1.4 ml/min) of 0.1 M H2SO4 passed to a gas diffusion cell, the ammonium ions passed into the H2PO4 and were determined by amperometry using a previously described electrode (Ruzicka and Hansen, 'Flow injection Analysis', John Wiley and Sons, New York, 1981, p. 207). The flow-through three-electrode cell contained a copper hexacyanoferrate film electrode coated with Nafion Film as the working electrode, a Ag/AgCl reference electrode and a Pt auxiliary electrode. An applied voltage of 0.4 V was used. The calibration graph was linear for 2-40 µM-ammonium ions. The method was applied to the determination of ammonium ions in lake and rain water with recoveries of 94.4-104.4% and RSD of 1.1-2.3% (n not given).
Ammonium Environmental Environmental Amperometry

"Flow Injection Analysis Of Sulfite By Gas-phase Molecular Absorption UV-VIS Spectrophotometry"
Talanta 1997 Volume 44, Issue 6 Pages 1009-1016
A. Safavi* and B. Haghighi

Abstract: Sample solution (200 µL) was injected into a carrier stream of water (1.9 ml/min) which merged with a stream (1.9 ml/min) of 1 M H2SO4 and passed through a mixing coil (50 cm x 0.5 mm i.d.). N2 (17 ml/min) was introduced into the merged stream and the evolved SO2 diffused into the N2 gas segments in a second mixing coil (30 cm). The SO2 was separated in a gas-liquid separator (diagram given) and passed to a flow cell (diagram given) where the absorbance was measured at 200 nm. The detection limit was 0.8 µg sulfite and calibration graphs were linear for up to 120, 120-240 and 240-440 µg. The RSD were 1.02% and 0.76%, respectively, for 70 and 220 µg sulfite. Sample throughput was 40/h. Little interference was observed. The method was applied to water and lemon juice. Recoveries were >=95.2%.
Sulfite Juice Water Spectrophotometry

"Determination Of Ammonium In Kjeldahl Digests By Gas Diffusion Flow Injection Analysis With A Bulk Acoustic Wave-impedance Sensor"
Talanta 1997 Volume 44, Issue 11 Pages 2121-2128
Xiao-Li Su, Li-Hua Nie and Shou-Zhuo Yao*

Abstract: A novel flow injection analysis (FIA) system has been developed for the rapid and direct determination of ammonium in Kjeldahl digests. The method is based on diffusion of ammonia across a PTFE gas-permeable membrane from an alkaline (NaOH/EDTA) stream into a stream of diluted boric acid. The trapped ammonium in the acceptor is determined on line by a bulk acoustic wave (BAW)-impedance sensor and the signal is proportional to the ammonium concentration present in the digests. The proposed system exhibits a favorable frequency response to 5.0 x 10^-6-4.0 x 10^-3 mol L-1 ammonium with a detection limit of 1.0 x 10^-6 mol L-1, and the precision was better than 1% (RSD) for 0.025-1.0 mM ammonium at a through-put of 45-50 samples h-1. Results obtained for nitrogen determination in amino acids and for proteins determination in blood products are in good agreement with those obtained by the conventional distillation/titration method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rates and potential interferents on the FIA signals were discussed in detail. (C) 1997 Elsevier Science B.V. 15 References
Ammonium Nitrogen Amino Acids Protein Blood Sensor

"Online Coupling Of Gas Diffusion To Capillary Electrophoresis"
Talanta 1998 Volume 45, Issue 3 Pages 477-484
Petr Kuban and Bo Karlberg*

Abstract: Online gas diffusion has been coupled to a capillary electrophoresis system (CE) via a specially designed interface. The sample is merged with a modifying solution, e.g., a strong acid, in a flow system to transform the analytes of interest into their respective gaseous forms. These transformed, gaseous analytes permeate through a PTFE membrane into an acceptor stream comprising of a tris-buffer. The continuously flowing acceptor stream is led into an injector forming an integrated part of a flow injection analysis (FIA) system. The sample receiving carrier stream in the FIA system, a chromate buffer, brings the sample, 50 µl, to the FIA-CE interface into which one end of a separation capillary has been inserted. A small portion of the injected sample enters the capillary (electrokinetic injection) and separation takes place. A UV detector is placed at the other capillary end and a run potential of 25 kV is applied to two platinum electrodes positioned in the flow system. Multiple sample injections can be performed in one uninterrupted electrophoretic run. A typical sampling frequency is 15 h-1; each run may result in quantitation of at least five anions. The overall repeatability is in the range 1.8-3.6% (RSD). The technique has been applied to the analysis of real samples such as soft drinks, vinegar and wine. Selective discrimination of anions which are unable to form volatile species is accomplished. No off-line sample pre-treatment is needed.
Anions Soft drink Food Wine Electrophoresis

"Dual-phase Gas-permeation Flow Injection Thermometric Analysis For The Determination Of Carbon Dioxide"
Talanta 1998 Volume 47, Issue 3 Pages 711-717
Shan-jun Liu and Matthieu Tubino*

Abstract: A flow injection configuration based on a dual-phase gas-permeation system from a liquid donor to a gas acceptor stream with a thermistor flow-through detector is proposed for the direct anal. of the gas in the acceptor. This system was applied for the determination of CO2 (as carbonate) using the following chemical reaction: CO2(g) + 2NH3(g) + H2O(g)=(NH4)2CO3(s), with a linear response from 1 x 10^-3 to 50 x 10^-3 mol 1-1 of CO32-. CO2 was produced in the liquid donor and permeated into the gaseous acceptor stream of air/H2O vapor. The detection limit is 1 x 10^-3 mol 1-1 of carbonate, and a sampling frequency of 60 h-1 is achieved with a relative standard deviation of 4.1% for replicate injections. The dual-phase gas-permeation flow injection manifold, along with the membrane and phase sepns., as well as the chemical reaction, provides enhanced selectivity when compared with the system employing a liquid acceptor stream, as serious interferents in this system, for instance, acetate and formate, among others, do not interfere in the proposed system.
Carbon dioxide Thermistor

"Direct Determination Of Calcium In Milk On A Non-segmented Continuous-flow System"
Analyst 1979 Volume 104, Issue 1238 Pages 419-424
W. D. Basson and J. F. van Staden

Abstract: The determination of calcium in milk has been adapted to a non-segmented continuous-flow procedure at a sampling rate of up to 180 samples per hour. The values obtained compare favourably with those obtained by atomic-absorption spectrophotometry.
Calcium Milk Spectrophotometry

"Comparison Of Tubular Polymeric PH And Ammonium-ion Electrodes As Detectors In The Automated Determination Of Ammonia"
Analyst 1985 Volume 110, Issue 4 Pages 371-376
Heung Lark Lee and Mark E. Meyerhoff

Abstract: The potentiometric responses of the cited automated gas-sensing electrode configurations to varying concentration. of ammonia-N (free gas plus NH4+) have been directly compared with use of five diluent solution (0.015 M Tris - HCl buffer of pH 8.5; 0.015 M NaOH - boric acid of pH 9.7; 0.015 M NaOH - Na2HPO4 or 0.0015 M NaOH of pH 11.1; and 0.015 M NaOH of pH 12.2). In both detection systems continuous-flow gas dialysis was used in conjunction with tubular polymer-membrane electrode detectors. In one method the pH of the flowing recipient stream (0.01 M or 0.001 M NH4Cl) leaving the dialyser was monitored; in the second, a buffered recipient stream (0.01 M Tris - HCl, pH 7.5) was used and NH4+ was detected. For each of the five diluents, the latter method offered improved detection limits (>100-fold), rectilinear response ranges and selectivity. Detection of NH4+ was more selective than detection of volatile amines. The reasons for these enhanced analytical characteristics are discussed in terms of NH3 flux through the gas-permeable membrane of the dialyser, and solution equilibria.
Ammonium, nitrogen Electrode Electrode Electrode Potentiometry

"Versatile Manifold For The Simultaneous Determination Of Ions In Flow Injection Analysis"
Analyst 1988 Volume 113, Issue 10 Pages 1551-1555
Peter C. Hauser, Susie S. Tan, Terence J. Cardwell, Robert W. Cattrall and Ian C. Hamilton

Abstract: A flow injection analysis system is described for the simultaneous determination in plant nutrient solution of K+, Ca(II), NO3- and Cl- by potentiometry, and NH4+ and PO43- by spectrophotometry. Diagrams of the manifold and the spectrophotometric transducer are given. Potentiometric measurements were made with PVC-based ion-selective membranes; the carrier stream was 0.2 M Na acetate buffer. Ammonium ion was determined by the gas diffusion method with use of cresol red and thymol blue. Absorbance was measured at 605 nm. The calibration graph covered the range from 0.5 to 25 mg L-1 as N. Phosphate was determined by the molybdenum blue method, with absorbance measurement at 820 nm; the calibration graph covered the range from 0.5 to 25 mg l-1. Results agreed well with expected values.
Potassium Calcium Ammonium Chloride Nitrate Phosphate Commercial product Electrode Electrode Electrode Electrode Potentiometry Spectrophotometry

"Flow Injection System For Online Potentiometric Monitoring Of Ammonia In Freshwater Streams"
Analyst 1989 Volume 114, Issue 11 Pages 1443-1447
Salvador Alegret, Juli&aacute;n Alonso, Jordi Bartrol&iacute; and Esteve Mart&iacute;nez-F&agrave;bregas

Abstract: The system involves mixing a sample stream with 1 M NaOH, passage of the mixture through a dialysis chamber to transfer NH3 via a gas diffusion chamber into 10 mM Tris (pH 7.5), and detection of NH4+ by an ion-selective electrode. The electrode construction involves in situ formation and direct casting of the sensing nonactin - PVC membrane on to an epoxy resin loaded with graphite. The calibration graph was rectilinear from 0.02 to 10 mM, and the limit of detection was ~1 µM. Over 30 samples could be analyzed in 1 h. The system involves mixing a sample stream with 1 M NaOH, passage of the mixture through a dialysis chamber to transfer NH3 via a gas diffusion chamber into 10 mM Tris (pH 7.5), and detection of NH4+ by an ion-selective electrode. The electrode construction involves in situ formation and direct casting of the sensing nonactin - PVC membrane on to an epoxy resin loaded with graphite. The calibration graph was rectilinear from 0.02 to 10 mM, and the limit of detection was ~1 µM. Over 30 samples could be analyzed in 1 h.
Ammonia Environmental Potentiometry Electrode Electrode

"Simultaneous Determination Of Hydroxylamine And Cyanide In Formulations Containing Pralidoxime Salts By Flow Injection"
Analyst 1990 Volume 115, Issue 9 Pages 1239-1242
David Utley

Abstract: A flow injection method is described for the simultaneous determination of cyanide and hydroxylamine which are known decomposition products of formulations containing pralidoxime salts used in the treatment of anticholinesterase poisoning. By using the diffusion of HCN from the carrier stream followed by amperometric detection, high selectivity and sensitivity and a wide dynamic range can be achieved. Hydroxylamine is determined by its oxidation with iodine to nitrite which can then be determined colorimetrically. The gas diffusion unit effectively acts as a stream splitter for the two analytes allowing their simultaneous determination from a single sample injection. The performance of the system and its applicability to thermally stressed pralidoxime solutions are described. The HCN was determined by diffusion from a carrier stream of 0.2 M citrate buffer (pH 3.2) into a collection stream of 0.1 M NaH2BO3. Amperometric detection with a Ag working electrode vs. Ag - AgCl was used. The response was rectilinear from 10 to 100 µg mL-1 of KCN and the coefficient of variation (n = 5) were 1.0% over the range studied. Hydroxylamine was determined in the same carrier stream by oxidation with a stream of iodine reagent followed by reduction of the excess iodine with 0.705 M NaAsO2 and determination of the NO2- by diazocoupling with a 0.2% naphthylethylenediamine solution Detection was at 540 nm. The response was rectilinear from 0.1 to 20 µg mL-1 of hydroxylamine, with a limit of detection of 0.03 µg mL-1. The coefficient of variation (n = 5) was 0.7% over most of the range but was 4.3% for 0.1 µg mL-1.
Hydroxylamine Cyanide Amperometry Electrode

"Indirect Determination Of Chloride By Gas Diffusion Flow Injection With Amperometric Detection"
Analyst 1991 Volume 116, Issue 1 Pages 49-52
Snezana D. Nikolic Emil B. Milosavljevic, James L. Hendrix and John H. Nelson

Abstract: A flow injection manifold was designed for the cited determination (diagram given). A continuous flowing donor stream containing Cl- in 3 M H2SO4 and saturated KMnO4 solution diffused through a Nafion membrane into a 10 mM H2SO4 acceptor solution and subsequently to a flow-through amperometric cell (maintained at 30°). Measurements were made with a three-electrode system consisting of Pt working and counter electrodes and a Ag - AgCl reference. The applied optimum potential was +0.30 V. The calibration graph was rectilinear up to 10 mM of Cl- and the coefficient of variation was 1% for 2 mM (n = 9). The sampling rate was 30 h-1. At a cell temperature of 50°C and an acceptor solution of 5 M H2SO4, the detection limit was 0.1 µM. The effects of interferents are discussed. The method was applied to drinking water.
Chloride Water Amperometry Electrode Electrode

"Differential Conductometry In Flow Injection. Determination Of Ammonia In Kjeldahl Digests"
Analyst 1991 Volume 116, Issue 8 Pages 841-845
Jarbas Jos&eacute; Rodrigues Rohwedder and Celio Pasquini

Abstract: A differential conductivity meter is described (with circuit diagram) that consists of a Wien bridge, a measurement bridge with instrumentation amplifier and circuit for adjustment of sensitivity and balance and precision rectifier and output buffer. The meter was used to amplify the difference in conductance between two twin flow cells in the flow injection determination of NH3 in Kjeldahl digests of vegetables. The flow injection manifold is described (diagram given). The acceptor stream was 0.5 mM HCl and the reagent streams were 3 M NaOH containing 1% EDTA. Sample solution was injected into one reagent stream which was subsequently mixed with a second reagent stream before being passed to the gas diffusion cell. The acceptor stream passed through the reference flow cell before passing through the gas diffusion cell. This stream then passed through the indicator flow cell. Results correlated well (r = 0.999) with those obtained by an interlaboratory study. The sampling rate was 90 h-1 with negligible carryover and no matrix effects.
Ammonia Vegetable Conductometry

"Conductimetric And Spectrophotometric Determination Of The Volatile Acidity Of Wines By Flow Injection"
Analyst 1992 Volume 117, Issue 5 Pages 917-919
R&aacute;vio Guimar&atilde;es Barros and Matthieu Tubino

Abstract: The method previously described by the authors (J. Assoc. Off. Anal. Chem., 1991, 74, 346) was applied. It involved the diffusion of acetic acid through a membrane into a stream of water and a conductivity cell or into a stream of bromocresol purple, pH 7.0, and measurement at 540 nm. The calibration graphs were rectilinear, or nearly so, from 0.02 to 0.10 g per 100 mL. The spectrophotometric method was simpler but the conductimetric method was faster. The usual methods for the determination of the volatile acidity of wines are relatively slow. A method was developed which provides results in a much shorter time. About 60 analyzes can be performed in 1 h. The conductimetric anal. consists of the injection of the wine sample into a de-ionized water stream which then flows past a poly(tetrafluoroethylene) membrane separator. The HOAc diffuses through the membrane into another water stream that passes through a conductivity cell. The spectrophotometric method is similar. The HOAc diffuses into a stream of Bromocresol Purple solution, at pH 7.0, which passes through a flow cell in a spectrophotometer set at 540 nm. Anal. results were similar to those obtained by the method of Jaulmes.
Acidity Wine Conductometry Spectrophotometry

"Flow-through (bio)chemical Sensors. Plenary Lecture"
Analyst 1993 Volume 118, Issue 6 Pages 593-600
Miguel Valc&aacute;rcel and Maria Dolores Luque de Castro

Abstract: A review is presented of the state-of-the-art and trends in biochemical and chemical sensors based on the integration of derivative analytical reactions, separation processes and detection. The generic features of flow-through (bio)chemical sensors are outlined. The integration of reactions (chemiluminescence, fluorescence) or separation methods (dialysis, gas diffusion, sorption, liquid - liquid extraction) with detection (optical, electroanalytical, mass thermal) is examined. Critical comparisons between matching probe-type and continuous-flow configurations are given. (89 references).
Chemiluminescence Fluorescence Electrochemical analysis Sensor Sample preparation

"Continuous-flow System For The Accurate Determination Of Low Concentrations Of Ammonium Ions Using A Gas-permeable Poly(tetrafluoroethylene) Tube Decontaminator And An Ammonia Gas-sensing Membrane Electrode"
Analyst 1994 Volume 119, Issue 8 Pages 1839-1842
Hirokazu Hara and Susumu Matsumoto

Abstract: A calibration procedure, based on a constant-dilution method, is described for the determination of low concentrations of ammonium ions. A stream of ultrapure water (2 ml/min) was merged with a reagent stream of 0.21 M NaOH (0.1 ml/min) and the residual NH3 thus formed was removed by passing the solution through a microporous gas-permeable PTFE tube immersed in 0.5 M H2SO4 and thermostatted at 30°C. A limited volume (0.02, 0.04, 0.1, 0.2 and 1 ml/min) of standard NH4Cl solution was then added to the purified water. The diluted standard solution (2 ml/min) passed to a mixing chamber and then to an NH3 gas-sensing membrane electrode for analysis. The concentration of ammonium ions was calculated and a calibration graph was constructed. A diagram of the continuous-flow system used is given. The measurable concentration range was 0.1-5 µM of ammonium ions; the RSD (n = 5) was 0.8-1.1%. The system was used to determine low concentrations of ammonium ions in lake water.
Ammonium Lake Electrode Electrode

"Determination Of Ninhydrin Positive Substances In Seawater And Hemolymph"
Analyst 1995 Volume 120, Issue 8 Pages 2097-2099
Saloua Sadok, Roger Uglow and Stephen J. Haswell

Abstract: A flow injection spectrophotometric method for determining ninhydrin positive substances (α-amino-acids) in seawater and in hemolymph from mussels (Mytilus edulis) is described. Hemolymph was diluted with saline before analysis; seawater was used directly. The sample (0.5 ml) was mixed with 1 mL 3% ninhydrin and heated in a boiling-water bath for 12 min, 1 mL 0.8 M HCl was added and the mixture was heated for a further 10 min. A portion (0.3 ml) of the solution was injected into an aqueous carrier stream (1 ml/min) and mixed with a stream (1 ml/min) of 1.2 M NaOH in a 15 cm mixing coil to produce NH3. The solution was then passed over a microporous PTFE membrane through which the NH3 diffused into a stream (1 ml/min) of 0.4 g/l Bromothymol Blue. The absorbance of the colored solution was measured at 635 nm. The calibration graph was linear up to 60 µM-alanine and the detection limit was 0.3 µM. The RSD (n = 6) was 2%. Recoveries were quantitative.
Amino acids, α Mussel Sea Spectrophotometry

"Flow Injection Amperometric Determination Of Trace Amounts Of Ammonium Using A Gas Diffusion Cell As The Sample Loop"
Analyst 1995 Volume 120, Issue 12 Pages 2845-2848
Renmin Liu, Bianting Sun and Ian Johns

Abstract: A new flow injection method for the determination of trace amounts of ammonium by using a pyrolytic graphite electrode electrodeposited with a cuprihexacyanoferrate film coated with Nafion film as a sensor is described. A gas diffusion unit was used to enhance the selectivity and sensitivity, Under optimum analytical conditions, the linear range of the calibration graphs for ammonium were 2-32, 0.8-16 and 0.4-8 µmol L-1 when the accumulation time was 1, 2 and 3 min, respectively, The method has been applied to the determination of ammonium in rain-water samples and recoveries of 96.7-102.2% were obtained, The s(r) values of seven replicate analyzes for all samples were 1.6-2.5%. (22 references)
Ammonia Rain Amperometry Electrode Electrode

"Determination Of Ammonia In Waste Waters By A Differential PH Method Using Flow Injection Potentiometry And A Nonactin-based Sensor"
Analyst 1997 Volume 122, Issue 1 Pages 89-93
Hongda Shen, Terence J. Cardwell and Robert W. Cattrall

Abstract: A water sample (20 µL) was injected into a water stream (0.9 ml/min) which merged with a stream (0.9 ml/min) of 0.6% acetic acid buffer of pH 6 containing 0.84% LiCl and 0.42% LiOH, then passed through a PTFE reaction coil (20 cm x 0.5 mm i.d.) prior to detection. The potential was recorded at a nonactin-based ammonium ion-selective sensor (fabrication described) vs. Ag/AgCl and a reference stream (0.9 ml/min) of 0.15 M LiCl (diagram of FIA system given). A second analysis was carried out, using LiCl/LiOH/0.75% boric acid buffer of pH 9.4 containing 0.84% LiCl, 0.42% LiOH and 5 µM-KCl in place of the pH 6 buffer. The difference between the potentials recorded with the different buffers was used to determine NH3 by a chemometric technique (details given). The use of this approach enabled the interference from moderate concentrations of K and Na to be corrected. Calibration graphs were linear (graphs shown) and the determination limit was ~1 µM. Recoveries and RSD are presented. The throughput was 30 samples/h. The method was applied to waste water and river water. The results were compared to those obtained by a gas diffusion technique.
Ammonia River Waste Potentiometry Electrode Sensor

"Determination Of Primary Explosive Azides In Environmental Samples By Sequential Injection Amperometry"
Analyst 1997 Volume 122, Issue 4 Pages 315-319
Roger T. Echols, Ryan R. James and Joseph H. Aldstadt

Abstract: A method for determining the azide ion in water is described. The sample (~333 µL) was loaded into a holding coil then propelled by a carrier (donor) stream of 0.01 M KCl in phosphate buffer of pH 3.78 at a flow rate of 1 ml/min to a gas diffusion unit. In the gas unit, HN3 diffused across a PTFE membrane into a static acceptor stream of 0.01 M KCl in phosphate buffer of pH 6.6. Diffusion of HN3 was enhanced by carrying out four reverse and forward flows of the sample zone, after which the flow of the acceptor stream was started at a rate of 1 ml/min. The analyte was detected amperometrically at a vitreous C electrode at 1 V vs. Ag/AgCl. A diagram of the manifold used is given. The calibration graph was linear up to 0.5 ppm azide; the detection limit was 24.6 ppb. RSD was 1.7-7.7% (n = 4). The method was applied to the analysis of lake, tap and groundwater.
Azide ion Water Ground Lake Amperometry Electrode

"Determination Of Trimethylamine In Fish By Pervaporation And Photometric Detection"
Analyst 1997 Volume 122, Issue 7 Pages 663-666
J. A. Garc&iacute;a-Garrido and M. D. Luque de Castro

Abstract: Two methods for trimethylamine determination in fish are described. In the first method (method A), the sample was extracted with TCA. The filtered extract was mixed with streams of formaldehyde and NaOH in a continuous-flow manifold before reaching a pervaporation cell kept at 60°C. The analyte evaporated and diffused through a PTFE membrane into a Bromothymol Blue solution of pH 6 and the color change was recorded. In the second method (method B), the sample was mixed with TCA, formaldehyde and NaOH directly in the pervaporation cell. After 5 min at 60°C, the analyte was collected in a Bromothymol Blue solution of pH 6 and the color change was recorded. The calibration graphs were linear for 2-30 mg/l and for 0.1-10 mg/g trimethylamine for methods A and B, respectively; the corresponding detection limits were 1.6 mg/l and 0.08 mg/g. The RSD (n = 11) were 3.5-4.3%. The throughputs were 8 and 2 samples/h for methods A and B, respectively.
Trimethylamine Marine Spectrophotometry

"Flow Injection Determination Of Sulfite In Wines And Fruit Juices By Using A Bulk Acoustic Wave Impedance Sensor Coupled To A Membrane Separation Technique"
Analyst 1998 Volume 123, Issue 2 Pages 221-224
Xiaoli Su, Wanzhi Wei, Lihua Nie and Shouzhuo Yao

Abstract: A flow injection analysis (FIA) method was developed for the rapid determination of sulfite in wines and fruit juices. The method is based on an online membrane separation of the SO2 released from a stream of 0.5 M H2SO4 into a stream of 0.01 M H2O2-0.15 mM H2SO4. The conductance increase due to the oxidation of SO2 to H2SO4 is monitored by a bulk acoustic wave impedance sensor and the signal is proportional to the concentration. of sulfite present in the original sample. At a throughput of 78 samples h-1, the method exhibited a linear frequency response up to 1.0 mM sulfite with a detection limit of 5.0 µM, and the relative standard deviation of the peak height (n = 6) ranged from 0.57 to 1.23. Results obtained by the proposed method agreed well with those obtained by conventional iodimetry. The effects of several factors, including those affecting the detector performance and gas transfer process, on the performance of the proposed FIA system were also examined
Sulfite Wine Fruit Sensor Conductometry Sensor

"Online Gas-diffusion Separation And Fluorimetric Detection For The Determination Of Acid Dissociable Cyanide"
Analyst 1998 Volume 123, Issue 2 Pages 217-220
Esther Miralles, Dolors Prat, Ramon Compa&ntilde;&oacute; and Merc&eagrave; Granados

Abstract: A flow injection system with gas diffusion separation and spectrofluorimetric detection is described for the determination of acid dissociable cyanide in water. Cyanide diffuses through a microporous PTFE membrane from an acidic donor stream into a sodium hydroxide acceptor stream. The cyanide transferred reacts with o-phthalaldehyde and glycine to form a highly fluorescent isoindole derivative Complete recovery of cyanide was found for Zn(CN)42-, Cu(CN)32-, Cd(CN)42-, Hg(CN)42-, Hg(CN)2 and Ag(CN)2- complexes and low recovery from Ni(CN)42-. No recovery was obtained from the species that are considered as non-free cyanide producing, viz., Fe(CN)64-, Fe(CN)63- and Co(CN)63-. The sampling frequency was 10 h-1 and the detection limit was 0.5 µg L-1. The method tolerates a 40-fold excess of sulfide. The results of cyanide determination in water samples obtained with the proposed method are consistent with those obtained with APHA Method 4500 CN- I for weak acid dissociable cyanide.
Cyanide, free Fluorescence

"Development Of A Biparametric Bioanalyzer For Creatinine And Urea. Validation Of The Determination Of Biochemical Parameters Associated With Hemodialysis"
Analyst 1998 Volume 123, Issue 6 Pages 1321-1327
M. Jurkiewicz, S. Alegret, J. Almirall, M. Garc&iacute;a and E. F&agrave;bregas

Abstract: The construction and evaluation of an automated urea and creatinine biparametric biosystem using flow injection analysis (FIA) are described. The biosystem uses enzyme reactions that hydrolyze urea and creatinine producing ammonium ions. The enzymes used were creatinine deiminase and urease, which are immobilized covalently in flow reactors. The reactor with creatinine deiminase has the enzyme immobilized on controlled-pore glass beads, whereas urease is immobilized on a nylon open tubular reactor. Detection is realized with a flow-through ammonium ion-selective electrode with an inner solid-state contact (graphite-epoxy composite). Ammonium ions are separated from alkali ion interferents through a gas-diffusion cell. The bioanalyzer is fully automated using software and electronics developed ex profeso in our labs. The analyzer was validated off-line by measuring urea and creatinine from discrete effluent samples from hemodialysis equipment. Results agreed with concurrent analyzes realized using hospital lab. methods. There were no significant differences between the two sets of results at the 95% confidence level. Finally, the biparametric bioanalyzer was validated online by measuring creatinine and urea levels in artificial kidney effluents. These measurements were useful in the determination of key biochemical parameters of clinical interest such as the mass of urea and creatinine extd. from the patient as well as the initial concentration. of creatinine and urea in blood plasma. When the results of the bioanalyzer were compared with those yielded by the usual methods, they showed no significant differences at the 95% confidence level when determining the mass of the analytes extd. by the hemodialyzer or when determining the urea concentration. in blood plasma. However, when measuring the creatinine concentration. in blood plasma using the developed bioanalyzer, significant differences appeared.
Creatinine Urea Blood Serum Haemodialysis Fluid Sensor Electrode

"Determination Of Germanium By Hydride Generation Inductively Coupled Plasma Atomic Emission Spectrometry Combined With Flow Injection"
J. Anal. At. Spectrom. 1988 Volume 3, Issue 4 Pages 579-582
Fumio Nakata, Hiroshi Sunahara, Hiroyoshi Fujimoto, Manabu Yamamoto and Takahiro Kumamaru

Abstract: The sample (20 to 40 mg) of single-crystal gallium arsenide was dissolved in HNO3 and the solution was diluted with water to 25 mL. A 1 mL aliquot was analyzed by a system (illustrated) consisting of a PTFE flow injection manifold by which the sample is mixed with sodium phosphate buffer (pH 6.5), NaBH4 solution and Ar (carrier gas), and a gas - liquid separator, constructed from micro-porous PTFE (cf. Yamamoto et al., Anal. Chem., 1987, 59, 2446), that delivers the generated hydrides directly into the sample introduction tube of the ICP torch (central orifice 0.6 mm i.d.) for determination of Ge at 265.18 nm. The calibration graph was rectilinear for 1 ng mL-1 to 10 µg mL-1 of Ge; the detection limit was 0.4 ng mL-1. By using the method of standard additions, recovery of 4 ng mL-1 of Ge from non-doped, Zn-doped and Si-doped gallium arsenide was satisfactory, but no indigenous Ge was detected. The method was also applied in the analysis of poly(ethylene terephthalate) (sample prep. described); recoveries were 90 to 120%, and 2.5 to 3.1 ng mL-1 of Ge was detected, which is better than the detection limit (5 ng mL-1) of the official method. The sample throughput was ~150 h-1.
Germanium Inorganic compound Polymer Spectrophotometry

"Determination Of Lead In Biological Materials By Microwave-assisted Mineralization And Flow Injection Electrothermal Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1993 Volume 8, Issue 2 Pages 235-241
J. L. Burguera and M. Burguera

Abstract: An automated online flow injection - electrothermal AAS system with microwave-assisted mineralization was designed. Certified reference biological materials were dispersed homogeneously in aqueous 0.4% Triton X-100 and mineralized with HCl - HNO3 in a PTFE coil located in a microwave oven followed by degasification in a gas diffusion cell and transfer of a precise volume by air displacement into a graphite furnace for AAS with drying for 20 s at 100°C and 10 s at 180°C, ashing for 30 s at 700°C and atomization at 2000°C for 5 s. The calibration graph was rectilinear up to 70 µg L-1 of Pb with a detection limit of 0.1 µg L-1 (0.8 pg). Sample throughput was 10 h-1. The results obtained compared well with certified values, except for botanical materials (recovery was ~90%).
Lead Plant Sample preparation Spectrophotometry

"Continuous-flow Fluorimetric Determination Of Ammonia In Water"
Anal. Chem. 1983 Volume 55, Issue 9 Pages 1620-1622
Toyoaki Aoki, Satoshi Uemura, and Makoto Munemori

Abstract: Sample and phthalaldehyde reagent (prepared as described by Lindroth and Mopper, Ibid., 1979, 51, 1667) were separately pumped at 2.1 and 0.23 mL min-1, respectively, into a tubular micro-porous PTFE membrane separator (cf. Aoki and Munemori, Ibid., 1983, 55, 209).To liberate NH3 at the optimum pH of 13, 1 M NaOH was added to the sample stream at a point just in front of the separator. The liberated NH3 permeated the membrane and entered the reagent stream, buffered at pH 9.5, in the inner tube.T he reaction product was fed to the flow cell of a fluorimeter for detection at 486 nm (excitation at 370 nm). Water was flushed through the apparatus (and used to establish the blank value) after each sample. The fluorescence intensity was proportional to the concentration. of NH3 in the range 0.2 µM to 0.2 mM; the detection limit was 18 nM. A study was made of interferences. The recovery of NH3 added to river water ranged from 95 to 105%.
Ammonia River Fluorescence

"Residual Aqueous Ozone Determination By Gas Diffusion Flow Injection Analysis"
Anal. Chem. 1985 Volume 57, Issue 9 Pages 1799-1803
Michael R. Straka, Gilbert Gordon, and Gilbert E. Pacey

Abstract: To determine residual 03 in treated water samples, an automated system of peristaltic pumps and injection valves was used to pass the aqueous test solution, at pH 2 (H2SO4), through a gas diffusion cell fitted with a micro-porous PTFE membrane, through which the 03 passed into (and decolorized) the colorimetric reagent. The decrease in absorbance was measured spectrophotometrically at 600 or 552 nm with use of K indigo trisulfonate or bis(terpyridyl)iron(II) reagent, respectively. Interference from Mn and H2O2 was eliminated, and that from Cl greatly reduced, by the diffusion technique. The indigo reagent was the more sensitive, and gave a detection limit of ~0.03 ppm of O3 and a rectilinear response up to 0.4 ppm.
Ozone Water Spectrophotometry

"Selective Determination Of Chlorine Dioxide Using Gas Diffusion Flow Injection Analysis"
Anal. Chem. 1985 Volume 57, Issue 14 Pages 2851-2854
David A. Hollowell, Gilbert E. Pacey, and Gilbert Gordon

Abstract: A Tecator Model 5020 flow injection analyzer. was used with a Tecator Chemifold V gas diffusion cell. The micro-porous membrane was a 0.45 µm pore-size PTFE membrane. The diffusion membrane separated the sample stream from the detector stream, and the ClO2 was detected at 359 nm with an ISCO spectrophotometer. The detection limit of ClO2 was 0.25 mg L-1 and the system was >550 times more selective for ClO2 than for Cl2. To further minimize the interference of Cl2, 0.83 M oxalic acid could be used in the acceptor stream, and this system had a detection limit of 0.45 mg L-1 of ClO2, but had 5400 times greater selectivity for ClO2 over Cl2.
Chlorine dioxide Water Spectrophotometry

"Dual Phase Gas Diffusion Flow Injection Analysis/hydride Generation Atomic Absorption Spectrometry"
Anal. Chem. 1986 Volume 58, Issue 2 Pages 502-504
G. E. Pacey, M. R. Straka, and J. R. Gord

Abstract: Flow injection manifolds are described in which HCl and NaBH4 enter the carrier stream and the resulting hydride diffuses through a PTFE membrane (7 cm x 1 mm; pore size 0.45 µm) supported by a nylon mesh in a modified Tecator gas diffusion cell. The hydride is then carried in a stream of H to a silica atomization cell of the type described by Dedina (Ibid., 1982, 54, 2097). The systems were used in the detection of As(III), one manifold providing for introduction of KI solution to reduce As(V). For 0.2 mL sample injections the limit of detection was 10 µg L-1 of As(III) and response was rectilinear up to 160 µg l-1. The principal advantage of the technique is the decreased interference by Co, Cu, Ni, Sb and Sn by comparison with the technique of Yamamoto et al. (Ibid., 1985, 57, 1382), while being simpler than the technique of Narasaki and Ikeda (Ibid., 1984, 56, 2059).
Arsenic(3+) Arsenic(5+) Water Spectrophotometry

"Flow Injection Analysis Of Phenols Via Bromination And Detection Of Unreacted Bromine At A Platinized Gas Diffusion Membrane Electrode"
Anal. Chem. 1986 Volume 58, Issue 4 Pages 983-985
Antonin Trojanek and Stanley Bruckenstein

Abstract: A portion of the test solution in 1 M H2SO4 is injected into a stream of 0.01 to 1 mM KBr - 50 mM KBrO3, and, after passage through a 60-cm reaction coil at 50°C, unreacted Br is determined amperometrically by reduction at a platinum gas permeable membrane electrode in a cell similar to that described previously (see earlier in this section). A potential of +0.30 V vs. the SCE is applied to the platinum electrode and the supporting electrolyte is 0.1 M H2SO4. The analytical range can be extended by appropriate changes in the concentration. of KBr in the carrier stream. With 0.1 mM KBr, calibration graphs are rectilinear for 10 to 200 ng of resorcinol, 20 to 300 ng of phenol and 30 to 650 ng of 2-naphthol. The reproducibility of production of Br by acidification of the composite reagent is 1.1% (n = 20). Alternatively, the Br can be introduced into the carrier stream by permeation, thus providing a possible means of post-column reaction for the detection of phenols in HPLC.
Phenols 2-Naphthol Amperometry HPLC Electrode Electrode

"Flow Injection Analysis Of Volatile, Electroinactive Organic Compounds At A Platinum Bas Diffusion Membrane Electrode By Use Of A Redox Mediator"
Anal. Chem. 1986 Volume 58, Issue 4 Pages 981-982
Antonin Trojanek and Stanley Bruckenstein

Abstract: The proposed procedure is based on the use of a detector cell similar to that described earlier (see section B of this issue, under nitrogen). In the determination of acetone, a portion of acetone solution is injected into a carrier stream (0.5 mL min-1) of water which passes to an electrochemical cell fitted with a platinum gas-permeable membrane electrode. Acetone diffuses through the membrane and causes reduction of Os(VIII) in the supporting electrolyte of the cell. The resulting Os(VI) is re-oxidized to Os(VIII) at the platinum electrode at an applied potential of +0.3 V vs. the SCE. Calibration graphs (oxidation current vs. concentration. of acetone) are rectilinear in the range 5 to 4000 ng, and at the 157 ng level the coefficient of variation is 0.8% (n = 12). Analyses of aqueous solution of methanol and ethanol also yield rectilinear calibration graphs. The sampling rate is 40 h-1.
Acetone Ethanol Methanol Amperometry Electrode Electrode

"Selective Chlorine Dioxide Determination Using Gas Diffusion Flow Injection Analysis With Chemiluminescent Detection"
Anal. Chem. 1986 Volume 58, Issue 7 Pages 1524-1527
David A. Hollowell, James R. Gord, Gilbert Gordon, and Gilbert E. Pacey

Abstract: The automated system includes a gas diffusion membrane which allows transfer of ClO2 but otherwise separates the sampling stream from the detector stream and also removes ionic interferents. The detector stream was merged with the reagent stream containing luminol and H2O2 at pH 9 just before entry into the flow-through detector cell for chemiluminescence measurement. The detection limit of ClO2 was ~5 ppb and the selectivity for ClO2 over Cl was >1500. Interference from Fe and Mn compounds and from other oxychlorine compounds was eliminated by this technique, which was devised for determination of ClO2 in waters.
Chlorine dioxide Environmental Chemiluminescence

"Membrane Gas-liquid Separator For Flow Injection Hydride-generation Atomic Absorption Spectrometry"
Anal. Chem. 1987 Volume 59, Issue 19 Pages 2446-2448
Manabu Yamamoto, Kazuko Takada, Takahiro Kumamaru, Makoto Yasuda, Shozo Yokoyama, and Yuroku Yamamoto

Abstract: A flow injection manifold with a membrane tube gas - liquid separator (illustrated) was applied in the determination of As in seawater. Thus, KI, HCl and ascorbic acid solution were added to the sample before injection of an aliquot (1 ml) into a stream of 1 M HCl and air (each 5 mL min-1). After being mixed with streams of Ar (100 mL min-1) and NaBH4 solution (3%; 1.5 mL min-1), the combined stream was passed through a micro-porous PTFE tube (o.d. 4 mm; i.d. 3 mm) inside a borosilicate glass tube (25 cm x 8 mm). The gaseous AsH3, H and Ar diffused through the PTFE tube walls and were passed to a heated silica cell at 950°C for the determination of As (Ibid., 1985, 57, 1382). In the determination of 3 ppb of As, the coefficient of variation was 2.5% (n = 10). There was little interference from up to a 2000- or 50,000-fold excess, respectively, of Pt or Ni.
Arsenic Sea Spectrophotometry

"Gas Diffusion Unit With Tubular Microporous Poly(tetrafluoro-ethylene) Membrane For Flow Injection Determination Of Carbon Dioxide"
Anal. Chem. 1987 Volume 59, Issue 24 Pages 2930-2932
Shoji Motomizu, Kyoji Toei, Tohru Kuwaki, and Mitsuko Oshima

Abstract: A gas diffusion unit was constructed, without the use of glue, from two T-connectors linked by double tubing consisting of a micro-porous PTFE membrane inner tube (1 mm i.d. x 1.8 mm o.d.) and an outer PTFE tube (2 mm i.d.). The tubing was fixed to the connectors by a flange-type union. A carrier stream (0.8 mL min-1) of 0.18 M H2SO4 flowed through the outer tube and a cresol red color reagent solution (0.8 mL min-1) flowed through the inner tube. Standard solution (140 µL) of NaHCO3 and river water samples were injected into the carrier solution and absorbance changes were measured at 410 nm. Results agreed with those obtained by indirect photometric ion chromatography.
Carbon dioxide River Spectrophotometry

"Selective Chlorine Determination By Gas Diffusion Flow Injection Analysis With Chemiluminescent Detection"
Anal. Chem. 1988 Volume 60, Issue 1 Pages 2-4
J. R. Gord, G. Gordon, and G. E. Pacey

Abstract: To determine dissolved free Cl (i.e., Cl2, ClO- and HClO) in water, the sample (0.35 ml) was injected into a donor stream (2.25 mL min-1) of 1 M HCl, from which Cl2 transferred through a 0.45 µm PTFE membrane into an acceptor stream (pH 11.75; 0.8 mL min-1) of 75 mM KOH, which was then mixed with 5 mM H2O2 - 1 mM lophine in ethanolic KOH (0.8 mL min-1) as chemiluminescence reagent to react with the ClO- formed. Rectilinear response was obtained for 175 ppb to 900 ppm of Cl, with a limit of detection of 75 ppb, and a coefficient of variation of 1.3%. Sample throughput was 120 h-1. A modified system was used for samples also containing ClO2.
Chlorine, free Chlorine dioxide Environmental Chemiluminescence

"Flow Injection Gas Diffusion Method For Preconcentration And Determination Of Trace Sulfide"
Anal. Chem. 1988 Volume 60, Issue 24 Pages 2791-2796
Emil B. Milosavljevic, Ljiljana Solujic, James L. Hendrix, and John H. Nelson

Abstract: Sample solution (1 to 5 ml) is injected into 0.1 M H2SO4 as carrier stream (1.2 mL min-1) and, after passing thorough a 30-cm reaction coil, the acidified sample flows through the donor channel of a gas diffusion separation unit. The liberated H2S diffuses across the PTFE membrane and is collected in 130 µL of 10 mM Na2CO3, which is continually recirculated at 0.3 mL min-1 through the acceptor channel. After pre-concentration. is complete, the acceptor solution is passed through a flow-through amperometric detector with Ag working and Pt counter electrodes, and the oxidation current is measured at 0.0 V vs. Ag - AgCl. The required flow patterns of the system are regulated by one 8-port rotary valve. With 1 mL sample injections, the calibration graph was rectilinear from 0.001 to 1 µg mL-1 of S2-; at 1 ng mL-1 the coefficient of variation was 4% (n = 5). With 5 mL sample injections, the limit of detection was 0.15 ng mL-1 of S2-. Of 13 foreign ions investigated, only CN- interfered seriously.
Sulfide Amperometry Electrode Electrode

"Simultaneous Photometric Flow Injection Determination Of Sulfide, Polysulfide, Sulfite, Thiosulfate And Sulfate"
Anal. Chem. 1991 Volume 63, Issue 5 Pages 427-432
Kim Sonne and Purnendu K. Dasgupta

Abstract: A complex manifold system is described (with diagram) for determination of the cited species in aqueous samples relevant to the petroleum industry. Samples are acidified to produce S from Sx2- and turbidity is measured to determine polysulfides; using a gas diffusion device, the liberated H2S is collected and determined with pentacyanonitrosylferrate(II) as colorimetric reagent as a measure of total sulfide and polysulfide. For sulfite determination sample solution is acidified to produce SO2 which is detected by decolorization of a triphenylmethane dye. For thiosulfate determination, Zn2+ and formaldehyde are added to the sample in a near-neutral medium; soluble constituents of the resulting stream are dialysed into slightly acidic permanganate solution and the decolorization is monitored. For sulfate determination, acidic BaCl2 is added to the sample stream and turbidity is measured.
Polysulfide Sulfate Sulfide Sulfite Thiosulfate ion Turbidimetry

"Determination Of Total And Free Sulfur Dioxide In Wine By Flow Injection Analysis And Gas Diffusion Using P-aminoazobenzene As The Colorimetric Reagent"
Anal. Chem. 1991 Volume 63, Issue 21 Pages 2532-2535
Jordi Bartroli, Manel Escalada, Cecilia Jimenez Jorquera, and Julian Alonso

Abstract: For the determination of free SO2, samples (0.3 ml) were injected into a stream of 0.6 M HCl, which then passed to the diffusion module, a poly(methacrylate) block, with a channel (7 cm x 2 mm) fitted with a gas-permeable poly(vinylidene fluoride) membrane. The SO2 diffusing across the membrane merged with the reagent stream, containing p-aminoazobenzene (I) and formaldehyde. The mixing coil after the diffusion module was 250 cm long to allow for the slow reaction of I with SO2. The reaction product was measured at 520 nm. For the determination of total SO2, samples (50 µL) were mixed with 4 M NaOH and the mixture passed into the loop of the injection valve, whence it was mixed with 0.6 M HCl as before. Agreement between direct and standard addition methods showed that there was no interference. Unlike p-rosaniline, the I was available pure commercially and the reagent solution was stable for at least a year.
Sulfur dioxide Wine Spectrophotometry

"Universal Sandwich Membrane Cell And Detector For Optical Flow Injection Analysis"
Anal. Chem. 1992 Volume 64, Issue 8 Pages 923-929
Jose Luis Perez Pavon, Encarnacion Rodriguez Gonzalo, Gary D. Christian, and Jaromir Ruzicka

Abstract: The cell (the outcome of several less practical designs as described previously) combined fiber optics, flow channels, spacers, reflecting surfaces and separation membranes to provide flow injection analysis in conjunction with spectrophotometry, gas diffusion, membrane separation and chemiluminescence aided by membrane diffusion. Its use was demonstrated by the determination of e.g., a dye, Co(III), OCl- and phenol. Spectrophotometric detection, chemiluminescence, gas diffusion, membrane separation, and their combinations have been successfully performed in a flow cell, which combines fiber optics, flow channels, spacers, reflecting surfaces, and separation membranes into a robust sandwich type sensing unit. Applications which include a separation step were carried out using a suitable membrane, which acted as an opaque surface, reflecting the transmitted light into a bifurcated optical cable.
Cobalt(III) Hypochlorite Phenol Chemiluminescence Spectrophotometry

"Selective Determination Of Gases By Two-stage Membrane-differentiated Flow Injection Analysis. Determination Of Trace Hydrogen Cyanide In The Presence Of Large Concentrations Of Hydrogen Sulfide"
Anal. Chem. 1992 Volume 64, Issue 10 Pages 1106-1112
Vlastimil Kuban and Purnendu K. Dasgupta

Abstract: Sample gases were passed through the outside of a membrane tube (10 cm x 1 mm) of porous poly(vinylidene difluoride), through the inside of which 50 mM NaOH was flowing. After absorption of acidic gases, the pH of the solution was reduced to 9.6 by addition of a carbonate buffer. The solution then flowed along the outside of a membrane tube (18 cm x 0.4 mm) of silicone rubber, with 25 mM NaOH (in static mode) on the inside. Under these conditions, HCN but not H2S diffused into the alkaline receptor. The HCN was determined spectrophotometrically with use of an isonicotinic acid - 1-phenyl-2-pyrazolin-5-one reagent and measurement at 544 nm. The calibration graph was rectilinear for 0.1 to 1.5 ppm of HCN (by volume), with a detection limit of 35 ppb. The presence of several thousand ppm of H2S did not interfere. Hydrogen cyanide at low ppb (volume) levels is determined in the presence of several thousand ppm (volume) H2S. The gases diffuse through a porous poly(vinylidene difluoride) tubular membrane into an NaOH absorber; the pH is then adjusted to 9.5-10, and the liberated HCN is selectively permeated across a tubular silicone rubber membrane into an NaOH absorber. A limit of detection (LOD) of 35 ppb (volume) HCN is attainable with a pre-concentration time of 10 min (through-put rate of 5 samples h-1) and spectrophotometric determination of cyanide by the Koenig reaction with sodium isonicotinate and 3-methyl-1-phenyl-2- pyrazolin-5-one.
Hydrogen cyanide Spectrophotometry

"Dual-detection For Optimization Of Gas Diffusion In Flow Injection Analysis. Determination Of Ammonium And Sulfide"
Fresenius J. Anal. Chem. 1987 Volume 329, Issue 6 Pages 714-717
G. Schulze, M. Brodowski, O. Elsholz und A. Thiele

Abstract: Using gas diffusion, ammonium and sulfide can be determined selectively by flow injection analysis. An estimation of the membrane transference is achieved by dual-detection. It permits the determination of the volatile component in both the donor and the acceptor stream. This is performed by use of a retardation loop in the case of sulfide. For ammonium, two gas diffusion units are coupled with each other. As a measure of the membrane transference the effectivity of transfer is defined, estimating 30-40% for hydrogen sulfide and ~7% for ammonia. An elevation of temperature to 80°C increases the membrane transference by a factor of 1.2 and 1.8, respectively. Different membranes were tested.
Ammonium Sulfide

"Application Of Flow Injection Techniques For The Analysis Of Inorganic Anions"
Fresenius J. Anal. Chem. 1985 Volume 320, Issue 5 Pages 451-456
J. M&ouml;ller and B. Winter

Abstract: A review is presented, with 113 references. Some improvements in the determination of sulfur anions by flow injection analysis are also described. A survey of applications of flow injection analysis for the analysis of inorganic anions is given in form of a table. The turbidimetric determination of sulphate is improved by the intermittent addition of a wash solution via a separate pump. A comparison of results for the determination of sulphate in surface waters using the barium-methylthymol blue method and ion-chromatography shows good agreement. For the determination of sulphite a gas-diffusion technique is used. The method allows 90 injections/h and shows good reproducibility, 1% RSD for consecutive injections of standards at the 10 mg/l SO2-level. As the sample line is physically separated from the detection line, the method is insensitive to matrix effects from colored or turbid samples. Results for the determination of free and total sulphite in wine, beer and fruit juices are given.
Anions Sulfur compounds Sulfate Sulfite Food Water Spectrophotometry

"Determination Of Ammonium In Aerosols, Cloud And Rain Water, And Of Gaseous Ammonia In The Troposphere"
Fresenius J. Anal. Chem. 1987 Volume 327, Issue 1 Pages 16-16
U. Sprenger and K. B&auml;chmann

Abstract: Four methods were compared for the determination of NH4+. An UV - visible spectrophotometric determination is described which involved treatment of NH4+ with an alkaline solution of 4,4'-bis-(3-methyl-1-phenylpyrazolin-5-one) in the presence of chloramine T at pH 6, extraction with trichloroethylene after acidification, and measurement of the absorbance at 455 nm. Two flow injection analysis methods are described involving injection of a sample into a stream of NaOH to produce NH3 which diffuses across a permeable membrane into a flowing acceptor stream. In the first method, the acceptor is bromothymol blue solution and the absorbance is measured at 620 nm, and in the second, the acceptor is water and the change in conductivity is measured. The last method described involves ion chromatography and conductivity detection. The sample volume, detection limits, reproducibilities and analysis times are given for the four methods. A possibility for sampling gaseous NH3 is by formation of ammonium oxalate on cellulose filters coated with oxalic acid.
Ammonium Gas Environmental Rain Cloud Spectrophotometry

"Dual Detection For Optimization Of Gas Diffusion In Flow Injection Analysis. Determination Of Ammonium And Sulfide"
Fresenius J. Anal. Chem. 1988 Volume 329, Issue 6 Pages 714-717
G. Schulze Contact Information, M. Brodowski, O. Elsholz und A. Thiele

Abstract: Flow diagrams are given for the flow injection determination of sulfide (as H2S) and ammonium (as NH3), with use of a gas-permeable membrane for analyte transfer from donor to acceptor stream. The efficiency of this transfer has been studied. For H2S, a retardation loop was used to connect the donor stream to the 644-nm detector for parallel monitoring of both streams; the efficiency was 30 to 40%. For NH3, two parallel gas diffusion unit - 578-nm detector systems were used; the efficiency was ~7%. At 80°C, the efficiency increased by factors of 1.2 and 1.8, respectively, over that at ambient temperature Two PTFE materials are recommended for membrane construction.
Ammonium Sulfide Spectrophotometry

"Removal Of Interferences In The Spectrophotometric Determination Of Cyanide By Dialysis Using Flow Injection Analysis"
Fresenius J. Anal. Chem. 1988 Volume 331, Issue 6 Pages 620-622
E. Figuerola, A. Florido, M. Aguilar and J. de Pablo

Abstract: The sample was mixed with 0.1 M HCl (0.25 mL min-1) in a flow injection system with a 50 to 500-cm coil, and the HCN formed passed through a Millipore 1-GVHP09050 membrane into 10 mM NaOH (0.4 mL min-1), portions (136 µL) of which were then injected into a stream of NaH2PO4 buffer solution (pH 6.3) and mixed with Chloramine T and a pyridine - barbituric acid reagent (cf. Rios et al., Anal. Abstr., 1985, 47, 5B70) in 76- and 476-cm coils, respectively, before measurement of the absorbance of the combined solution (0.8 mL min-1) in a flow cell at 582 nm. Calibration graphs were rectilinear from 0.1 to 5 mg L-1 of CN-; the detection limit was 70 µg L-1 of CN-. In the determination (at 10 samples h-1) of 2.5 mg L-1 of CN-, the coefficient of variation was 0.8% (n = 12). In determination of 5 mg L-1 of CN-, there was no interference from a 100-fold molar excess of SO42- or NH4+, a 40-fold molar excess of Cu(II), Cd or Zn or a 10-fold excess of Br-, Cl-, S2- or SCN-, but a 100-fold molar excess of CO32-, a 60-fold molar excess of Co(II) or Fe(III) or a 40-fold excess of Ni did interfere. The method should be applicable to waste water.
Cyanide Waste Spectrophotometry

"Gas Diffusion Separation And Flow Injection Potentiometry"
Fresenius J. Anal. Chem. 1990 Volume 336, Issue 1 Pages 21-28
Wolfgang Frenzel

Abstract: The similarities and differences between gas-sensing ion-selective electrodes and gas diffusion separation - flow injection potentiometry are discussed with emphasis on selectivity and sensitivity. Examples of the latter method are described. For the determination of NH4+, a liquid sample stream containing 10^-8 to 10^-5 M NH4+ is mixed with 1 M NaCl in 0.1 M NaOH and passed at 1.7 mL min-1 through a grooved diffusion cell with a membrane of microporous polypropylene tubing, NH4+ is adsorbed in Tris-buffer (pH 7.5) and detected with an NH4+ sensitive liquid membrane electrode. The method was also applied in the determination of CN-, sulfide and gas-phase nitrogen oxides.
Potentiometry

"Membrane-based Gas Sampling And Analysis Coupled To Continuous-flow Systems"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 10 Pages 817-821
Wolfgang Frenzel

Abstract: A detection system suitable for monitoring gaseous pollutants is described consisting of a membrane-based (hydrophobic polypropylene microtubing for tubular membranes or polypropylene or poly(vinylidene) difluoride for flat membranes) sampling unit which is an integral part of continuous-flow or flow injection systems (schematic given). Collection of the gaseous contaminants takes place by diffusive sampling under laminar flow conditions. Two geometrically different sampling devices, viz., tubular and planar arrangements are presented and the influence of experimental variables on collection and detection capabilities is discussed. The device may be applied to the detection of gases in air and the atmosphere and also in emission control. A detection system suitable to monitor gaseous pollutants is described. It consists of a membrane-based sampling unit which is integral part of a continuous-flow or flow injection systems. Collection of the gaseous contaminants takes place by diffusive sampling under laminar flow conditions. Two geometrically different sample devices (i.e., tubular and planar arrangements) are presented and the influence of experimental variables on collection and detection capabilities is discussed. The concept is shown to be used with numerous detection schemes. The field of application reaches from the determination of trace constituents in the atmosphere to the use in emission control.
Environmental

"Potentiometric And Conductometric Determination Of Ammonium By Gas Diffusion Flow Injection Analysis"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 4-5 Pages 276-280
Wolfgang Frenzel Contact Information and Cheng-Yu Liu

Abstract: Sample in water carrier stream was merged with a 0.1 M NaOH reagent and the mixture was consequently merged in the gas diffusion cell with an acceptor stream of 0.02 M Tris - HCl buffer of pH 8 or of boric acid - NH4OH for potentiometric or conductometric detection. A liquid membrance ammonium-selective electrode was used for potentiometric detection in the 0.1 µM to 1 mM range. Both potentiometric and conductometric detection give similar selectivity and sensitivity, but the latter gave a linear rather than logarithmic response. Considerable enhancement of selectivity in the potentiometric and conductometric determination of ammonium is provided by gas diffusion separation in flow injection analysis Ammonium and potassium selective liquid membrane electrodes can be used for determination in the concentration. range 10^-7 - 10^-2 mol/L with high precision and fast sample throughput. No interferences are encountered in the presence of ionic species and molecules that likely adsorb when the sensors are in direct contact with the sample. The selectivity over volatile amines is enhanced due to kinetic discrimination. Conductometric detection is shown to be as sensitive as the potentiometric detection. A major advantage, however, is the linear rather than logarithmic relationship between concentration and conductivity.
Ammonium Conductometry Potentiometry Electrode

"Efficient Flow Injection System With Online Gas Diffusion Preconcentration For The Determination Of Trace Amounts Of Ammonium-nitrogen At .mu.g/l Levels By Spectrophotometry"
Fresenius J. Anal. Chem. 1993 Volume 347, Issue 3-4 Pages 103-106
Shihua Fan, Hanswilly M&uuml;ller, Bettina Schweizer and Wolfgang B&ouml;hme

Abstract: Streams of sample solution and 0.1 M NaOH merged in a PTFE coil (30 cm x 0.5 mm i.d.) and passed to a gas diffusion unit fitted with a PTFE membrane through which the liberated NH3 passed into an absorption solution, which was stationary during the 30 s absorption period and was then pumped to the 1 cm detector cell for absorbance measurement at 590 nm. The calibration graph was linear for 1-100 ng/ml of ammonium-N and the detection limit was 0.8 ng/ml. The RSD (n = 10) at 10^-15 ng/ml were 1.5-2.8%. The recoveries of 20 ng/ml of ammonium-N added to lake water were 94-112%. The sampling frequency was 60-80 samples per h.
Ammonia, nitrogen Lake Spectrophotometry

"Determination Of Sulfite In Wine By Flow Injection Analysis With Indirect Electrochemical Detection"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 6 Pages 469-472
N. T. K. Thanh, L. G. Decnop-Weever and W. T. Kok

Abstract: Wine was diluted 50-100-fold with 0.1 M H2SO4 in 10% ethanol. A 0.13 l portion was injected into a carrier of the same composition as the diluent. The carrier flowed over a 45 µm thick permeable PTFE membrane and the SO2 diffused into an acceptor stream of acetate buffer of pH 4.7. This merged with a reagent stream, containing 5 mM KI, which was oxidized electrochemically at 5 or 25 µA, to provide an iodine solution All streams were pumped at 0.5 ml/min; this gave an iodine concentration of 0.78 or 3.9 µM. After the reaction with SO2, the unconsumed iodine was detected amperometrically. With the 5 µA generating current, the linear range was 0.05-2 ppm; at 0.9 ppm, the RSD was 1.6%. The results compared well with those obtained by titrimetry.
Sulfite Wine Amperometry

"Evaluation Of A Diffusive Sampling Method For The Determination Of Atmospheric Ammonia"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 1 Pages 19-26
Wolfgang Frenzel, Ewald Grimm and Gesa Gruetzmacher

Abstract: NH3 was collected in H3PO4 coated bottoms of glass phials followed by FIA. The samplers (3 at each site) were covered with a hydrophobic microporous membrane (PTFE tape) and hung upside down. After exposure, the tube-type samplers were opened under NH3-free air and 1 mL water was pipetted into each phial. After shaking, a 320 µL portion of the solution was pipetted into FIA system. Sample was mixed with a water carrier stream (1.4 ml/min) via an FIA manifold (schematic given) and 10 g/l NaCl in 1 M NaOH (0.4 ml/min) in a mixing coil. The resulting stream was mixed with an acceptor stream of 0.1 g/l bromocresol purple (0.6 ml/min) in a gas diffusion unit comprising channels (33 cm x 3 mm width x 0.1 mm depth). Detection was spectrophotometrically at 585 nm. The calibration range was linear from 0.5-100 µg/l (as NH3) and RSD were 1-3%. The standard deviation (n = 30) of the method was 0.33 ng and the sampling frequency was 20 samples/h. The detection limit under optimized conditions was 2.3 x 103:m3 s. The method was applied to outdoor and indoor measurements.
Ammonia Indoor Outdoor Spectrophotometry

"Simultaneous Flow Injection Determination Of Ammoniacal Nitrogen And Chloride In Industrial Effluent Water With A Combined Online Gas Diffusion/dialyser Unit"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 8 Pages 758-761
Jacobus F. van Staden, Cornelius J. Hattingh and Daniel Malan

Abstract: Industrial effluent was injected into a carrier stream (2.5 ml/min) of water, the stream was mixed with a stream (1.2 ml/min) of 0.1 M NaOH in a mixing coil (100 cm x 0.76 mm i.d.). The resulting stream passed into a gas diffusion/dialyser unit. The unit has two recipient channels; the top channel is separated from the donar channel with a PTFE membrane and contains ammoniacal indicator mixture (2.5 ml/min). The bottom channel is separated from the donar channel with a dialysis membrane and contains water (2.5 ml/min). The ammonical nitrogen stream passed through a coil (200 cm x 0.76 mm i.d.) and the absorbance was measured at 590 nm. The water dialysic stream was merged with a color stream (1.2 ml/min) containing mercury(II) thiocyanate in methanol, concentrated nitric acid and iron(III) nitrate in water. The resulting mixture passed through a coil (200 cm x 0.76 mm i.d.) and the absorbance of the chloride was measured at 480 nm. Calibration graphs were linear for 0.1 g/l ammonical nitrogen and 0-2.531 g/l chloride with RSD (n = 15) of 0.16-0.98% and 0.16-0.45%, respectively.
Ammonia, nitrogen Chloride Industrial Spectrophotometry

"A Flow Analysis System With An Amperometric Detector For The Determination Of Hydrogen Sulfide In Waters"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 2 Pages 169-172
Paul Jeroschewski and Sabine Braun

Abstract: Hydrogen sulfide (I) was liberated from aqueous samples with an acidic carrier solution and the mixed streams subsequently mixed with N2 (1.78 ml/min) prior to passage through a coiled glass capillary (60 cm x 2 mm i.d.) extraction unit. These dimensions were necessary to ensure an equilibrium exchange of I from the liquid phase to a series of N2 bubbles (28 µL) in accordance with Henry's law. The liquid stream and N2 bubbles passed into an electrochemical sensor (described and illustrated) constructed to ensure that only H2S in the gas phase was able to permeate through a microporous PTFE membrane into alkaline ferricyanide. The current necessary to re-oxidize the resultant ferrocyanide depended directly on the concentration of I. The dynamic range, under the above conditions, was 1-750 µM-I with an RSD of 3%.
Hydrogen sulfide Water Amperometry

"Flow Injection Determination Of Lead By Hydride Generation And Conductometric Detection"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 2 Pages 141-143
P. C. Hauser and Zhi-Ping Zhang

Abstract: Plumbane produced from the lead analyte in a flow injection manifold by reaction with sodium borohydride is passed through a porous poly(tetrafluoroethylene) membrane in a gas diffusion cell. The hydride reacts with bromine in the acceptor stream resulting in ionization which is detected by conductivity measurement. Direct mixing of the carrier with a reagent stream yields a limit of detection of approximately 1 mg/L. An improved detection limit of about 200 µg/L can be achieved by the incorporation of an auxiliary stream containing persulfate as oxidizing agent. The application of the method to the determination of lead in road dust and soil samples is demonstrated. The flow injection method was based on the reaction of PbH4 with Br2 to yield bromide ions which were detected by conductivity measurement. A sample of 75 µL was injected into a 0.04 M HNO3 carrier stream which was merged with the reagent stream, 0.3% NaBH4 in 0.05% NaOH. After passing through a reaction coil (60 cm x 0.5 mm i.d.), the flow was propelled to the gas diffusion cell where the liberated PbH4 diffused through a PTFE membrane and was collected in a 0.6 mM Br2 acceptor stream. The acceptor stream was propelled to the conductivity detector where the ionization was detected. All flow-rates were 0.3 ml/min. The calibration graph for Pb was linear for 2-12 mg/l, the detection limit was 1 mg/l and RSD (n = 5) were 3%. The method was applied to the determination of Pb in urban road dust and soil following sample preparation by a standard acid digestion procedure. The results were in agreement with those obtained by AAS.
Lead Environmental Road Conductometry Sample preparation Spectrophotometry

"Determination Of Acetaldehyde In Liquid, Solid And Semi-solid Food After Pervaporation-derivatization"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1168-1173
I. Papaefstathiou, U. Bilitewski, M. D. Luque de Castro

Abstract: A continuous-flow configuration was coupled to a pervaporation unit (details and diagram given). Liquid samples (e.g fruit juices) were injected into a water stream and led to the lower part of the thermostated laboratory-made pervaporation unit which has been described previously (Ibid., 1996, 354, 442). The volatile analyte evaporated and diffused through a hyrophobic PTFE membrane then was accepted by a stream of fuchsin in ethanol/H2SO4. The outlet of the upper acceptor chamber was merged with a stream of sodium sulfite solution. The resultant colored product (alkylsulfonic acid chromophore) was monitored spectrophotometrically. Procedures for analyzing semi-solids (e.g, yogurt) and solids (e.g, bread) are described. Sensitivity could be varied by altering the pervaporation temperature and the membrane thickness. Detection limits were 4.2 µg/ml; RSD were 1.2-3.6% (n=7-10)
Acetaldehyde Fruit Spectrophotometry

"Gas Permeation Continuous-flow Coulometric Analysis: Determination Of Sulfur Dioxide"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1045-1049
S. Liu, Han-xi Shen, Jian-xing Feng, Matthieu Tubino

Abstract: A gas permeation system is presented which has two gaseous streams on both sides of a membrane (schematic given). Ambient air was passed through silica-gel and activated C scrubbers then entered the acceptor side of the permeation cell. Sulfur dioxide samples entered directly on the donor side; flow rates were controlled using two adjusting valves. Measurements were carried out using a three-electrode dynamic coulometric detector. The effects of donor flow rates, gas pressure and membrane thickness on the signal are discussed. Calibration graphs were linear from 10^-6 up to 10^-3 mol/mol SO2/air; RSD was 1.3% (n = 7).
Sulfur dioxide Environmental Coulometry

"Flow Injection System With Gas Diffusion For The Sequential Determination Of Total Nitrogen And Phosphorus In Vegetables"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 5 Pages 657-662
Jos&eacute; L. F. C. Lima, Antonio O. S. S. Rangel, M. Renata S. Souto

Abstract: Dried, ground vegetables were digested with Se and H2SO4/salicylic acid/H2O2 and then diluted in 0.8 M H2SO4. A portion (180 µL) of the solution was injected into a stream of 0.8 M H2SO4, which merged with a stream of 2.5 M NaOH and passed through a gas diffusion unit. The NH3 diffused into a secondary stream of 0.01 M Tris hydrochloride of pH 7.5 which converted it to ammonium prior to detection with an ISE. The primary stream, now purged of NH3, passed through a stream splitter to reduce the total flow and then merged with a stream containing ammonium molybdate, stannous chloride and hydrazine sulfate in H2SO4. The primary stream then passed through a flow cell for determination of phosphate at 710 nm. The calibration graphs were linear from 0.34-2.4 mM phosphate and up to 0.11 M ammonium, the detection limits were 43 µM phosphate and 1.4 mM ammonium, and the RSD (n = 10) were <3.5%. The sampling rate was 40-60/h. The ammonium and phosphate levels were indicative of the total N and P contents of the vegetables analyzed.
Nitrogen Phosphorus Vegetable Electrode Sample preparation Spectrophotometry

"Flow Injection Analysis Based On A Membrane Separation Module And A Bulk Acoustic Wave Impedance Sensor. Determination Of The Volatile Acidity Of Fermentation Products"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 2 Pages 272-274
Xiaoli Su, Lihua Nie, S. Yao

Abstract: A novel flow injection analysis (FIA) system has been developed for the rapid determination of the volatile acidity of some fermentation products like vinegars and juices. The proposed method is based on the diffusion of volatile acids, mainly acetic acid, across a PTFE gas-permeable membrane from an acid stream into an alkaline stream, and the acids trapped in the acceptor solution are determined online by a bulk acoustic wave impedance sensor based on changes in the conductivity of the solution It exhibited a linear frequency response up to 10 nmol L-1 acetic acid with a detection limit of 50 µmol L-1, and the precision was better than 1% (RSD) at a through-put of 72 hr-1. The effects of operating voltage for the detector, cell constant of the electrode, composition of acceptor stream, flow rates, and temperature on the FIA performance were also investigated.
Acidity, volatile Acetic acid Food Fruit Conductometry Sensor Sensor

"A Novel Flow Injection System For Simultaneous Determination Of Nitrate And Nitrite Based On The Use Of A Zinc Reductor And A Bulk Acoustic Wave Impedance Detector"
Microchem. J. 1998 Volume 59, Issue 3 Pages 341-350
Xiao-Li Su, Po Chen, Xiao-Ge Qu, Wan-Zhi Wei and Shou-Zhuo Yao

Abstract: A novel flow injection system was developed for the simultaneous determination of nitrate and nitrite present in water, foodstuffs, and human saliva. The system is based on the use of a Zn-filled reduction column and a bulk acoustic wave impedance sensor (BAWIS) as detector. With water as carrier stream, both nitrate and nitrite are converted online to NH3, whereas with sulfamic acid, only nitrate is converted to NH3. The NH3 formed diffuses across a PTFE membrane and is trapped in an acid stream causing a change in the solution conductance, which was monitored by a BAWIS detector. At a throughput of ~60 h-1, the proposed system exhibited a linear response to the concentration. of nitrate and nitrite from 2.5 µM to 1.00 mM, with detection limits of 1.7 and 1.8 µM, respectively, and the relative standard deviation of the peak heights (n = 6) ranged between 0.83 and 1.75% for the entire working range. In anal. of real samples, the simultaneous determination of nitrate and nitrite was achieved by the proposed method with a simple change of the carrier stream between water and sulfamic acid, and the results agreed well with those of conventional colorimetry. (c) 1998 Academic Press.
Nitrate Nitrite Water Food Saliva Conductometry Sensor

"Reagentless Flow Injection Determination Of Ammonia And Urea Using Membrane Separation And Solid Phase Basification"
Microchem. J. 1998 Volume 59, Issue 3 Pages 372-382
James R. Akse, John O. Thompson, Richard L. Sauer and James E. Atwater

Abstract: Flow injection analysis instrumentation and methodology for the determination of NH3 and ammonium ions in an aqueous solution are described. Using inline solid phase basification beds containing crystalline media, the speciation of ammoniacal N is shifted toward the un-ionized form, which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-H2O-containing analysis stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analysis stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 µg/L and a dynamic concentration. range spanning three orders of magnitude using a 315 µL sample injection volume Using immobilized urease to enzymatically promote the hydrolysis of urea to produce NH3 and CO2, the technique was extended to the determination of urea.
Ammonia Urea Waste Conductometry

"Flow Injection Analysis Of Serum Urea Using Urease Covalently Immobilized On 2-fluoro-1-methylpyridinium Salt-activated Fractogel And Fluorescence Detection"
Anal. Biochem. 1990 Volume 188, Issue 2 Pages 325-329
D. Narinesingh, R. Mungal and T. T. Ngo

Abstract: Serum samples were analyzed for their urea content using fluorescence flow injection analysis incorporating an immobilized urease bioreactor and a gas permeable separator. The urease was immobilized under mild and facile conditions to a hydrophilic 2-fluoro-1-methylpyridinium-activated support. The ammonia released as a result of urease-catalyzed urea hydrolysis diffused through a gas permeable membrane into a constant stream of o-phthaldehyde solution to form a highly fluorescent product with lambda ex at 340 nm and lambda em at 455 nm. Up to 25 serum samples can be analyzed per hour. The within-day coefficient of variation (CV) was 1.12% and the day-to-day CV was 1.25% for serum containing 10.50 mg urea nitrogen dl-1. The bioreactor shows excellent storage (at 4°C) and operational stabilities (at 37°C). Urea was determined in serum by flow injection analysis (illustrated) with urease immobilized on 2-fluori-1-methylpyridinium toluene-4-sulfonate-activated Fractogel. The ammonia released diffuses through a gas-permeable membrane into a stream of phthalaldehyde. The fluorescence of the resulting product is measured at 455 nm (excitation at 340 nm). Calibration graphs were rectilinear up to 1400 mg dl-1 and the detection limit was 0.1 mg dl-1. Recovery was 98 to 103% and coefficient of variation were 1.5%.
Urea Blood Serum Fluorescence

"Flow Injection Determination Of Ammonia-N Using A Polymer Membrane Electrode-based Gas Sensing System"
Anal. Lett. 1981 Volume 14, Issue 6 Pages 415-432
M. E. Meyerhoff; Yvonne M. Fraticelli

Abstract: A new potentiometric gas sensing concept is used in conjunction with a flow injection technique to rapidly determine ammonia-nitrogen in the 10-5 to 10-2 mol/L range. The system designed utilizes a novel tubular flow-through PVC-nonactin membrane electrode to detect ammonium ions formed in a recipient buffer stream as the sample flows through a gas dialysis unit. At least 30 samples/h can be determined with good precision (≤7%) for samples ≥10-5 mol/L in ammonia-N. Preliminary data concerning the analytical application of this system for blood ammonia-N measurements is presented. A novel gas dialysis method for removing ammonia from blood samples is also described.
Ammonium, nitrogen Blood Clinical analysis Electrode Electrode Electrode

"Determination Of Urea In Undiluted Blood Samples By Flow Injection Analysis Using Optosensing"
Anal. Lett. 1987 Volume 20, Issue 12 Pages 1977-1994
Petersson, B.A.;Andersen, H.B.;Hansen, E.H.

Abstract: The flow injection manifold is described and illustrated. It incorporates a hydrophobic gas-permeable membrane and a hydrophilic membrane between which is contained a gel of covalently immobilized urease. The carrier solution is 0.1 M Tris buffer (pH 9.2). The NH3 generated enzymatically is detected by absorbance at 635 nm of an acceptor solution containing 0.04% of bromothymol blue in aqueous 24% ethanol (pH 6.2 to 6.3) that flows past the gas-permeable membrane. The calibration graph is rectilinear up to 6 mM urea; the standard deviation was <2% (n = 160). Variation in pH (of physiological magnitude) did not affect the analysis. The activity of the membrane sandwich remained constant for 7 days of operation.
Urea Whole Spectrophotometry

"Utilization Of Dual Phase Gas Diffusion Flow Injection Analysis With A Mass Spectrometer As A Detector"
Anal. Lett. 1988 Volume 21, Issue 9 Pages 1619-1631
J. S. Canham; G. E. Pacey

Abstract: Hydrides of As and Se were generated in aqueous solution from which they diffused through a Goretex micro-porous membrane (0.45 µm pore size) into dry He for detection by MS. No mixed hydrides were observed. The detection limit for As was ~500 ng; that for H2Se was 1 µg. Tin and Sb were easily detected and did not interfere.
Arsenic Selenium Mass spectrometry

"Flow Injection Spectrophotometric Determination Of Free And Total Sulfite In Wines Based On The Induced Oxidation Of Manganese(II)"
Anal. Lett. 1998 Volume 31, Issue 13 Pages 2195-2208
Rosa Lina G. N. P. Silva; Cintia S. Silva; Joaquim A. N&oacute;brega; Eduardo A. Neves

Abstract: The sulfur(IV) content in wines was determined with a flow injection spectrophotometric system by treating each sample in the donor channel with sulfuric acid to release free SO2, which diffuses through a PTFE membrane to the acceptor solution containing Mn(II) in acetate buffer at pH 5.5. The induced oxidation of Mn(II) takes place proportionally to the free S(IV) content and the oxidized species formed reacts with iodide to form iodine which can be spectrophotometrically measured at 352 nm. A linear plot of absorbance vs. S(IV) concentration. is observed up to 26 mg SO2/L with a detection limit of 1.0 mg/L. Matrix effects required the standard additions of sulfite to the samples for obtaining accurate results. A previous treatment of the sample with tris(hydroxymethylaminomethane) and EDTA decomposed the hydrogen-sulfite/aldehyde adducts and allowed the determination of the total S(IV) content. As expected, total S(IV) concentration. in wines has been found to be much higher than free sulfite. A recovery-addition experiment with red and white wines led to recoveries varying from 91.5 to 109.7% by applying the free and total sulfite developed procedures. This is a good indication of the accuracy of both proposed procedures.
Sulfite Wine Red Wine White Spectrophotometry

"Flow-through PH ISFET As Detector In Automated Determinations"
Electroanalysis 1991 Volume 3, Issue 4-5 Pages 349-354
S. Alegret, J. Bartrol&iacute;, C. Jim&eacute;nez, M. del Valle, C. Dom&iacute;nguez, E. Cabruja, A. Merlos

Abstract: A pH ISFET described previously (cf. Ibid., 1991, 3, 355) was installed in a specially designed flow-through cell (illustrated) and used together with a Ag - AgCl reference electrode in two different flow injection systems. The pH behavior of the sensor was tested by injecting sample into a pH 7 carrier buffer solution before mixing and measurement in the detection cell. The device exhibited near-Nernstian response from pH 3 to 11 and the calibration graph was rectilinear (r = 0.9975); the coefficient of variation was 1%. The device was applied in the determination of NH3 and SO2 with use of a gas diffusion unit with a polyvinylidene fluoride membrane. The pH of the carrier streams were modified with 1 M NaOH or 0.6 M HCl for determination of NH3 or SO2, respectively. Calibration graphs were rectilinear from 0.1 to 10 mM NH3 and 0.07 to 4 mM SO2 with corresponding coefficient of variation of ~1% and 0.5%.
pH Electrode Field effect transistor

"Continuous Separation Techniques In Flow Injection Analysis. A Review"
J. Chromatogr. A 1987 Volume 393, Issue 1 Pages 3-23
Miguel Valcarcel and M. Dolores Luque De Castro

Abstract: A review is presented of gas - liquid, liquid - liquid and liquid - solid separation techniques, and their applications in flow injection analysis. Particular attention is paid to the online coupling of HPLC and flow injection analysis. Examples are given. (122 references).
Spectrophotometry

"Online Monitoring Of Urea In Effluent Liquid During Haemodialysis"
J. Pharm. Biomed. Anal. 1993 Volume 11, Issue 10 Pages 921-926
A. Orellana, E. Mart&iacute;nez-F&agrave;bregas and S. Alegret*

Abstract: A flow injection potentiometric biosensing system (diagram given) for the determination of urea in dialysis effluent from a haemodialysis machine is described. Sample was injected into a carrier stream of dialysis liquid (details given) before passing through a urease bioreactor in order to convert urea to ammonium. The resulting stream was merged with a stream of 1 M NaOH (0.2 ml/min) before passing through a diffusion module where NH3 in the stream diffused through a gas-permeable membrane into a stream of 0.01 M Tris hydrochloride buffer solution of pH 7.5 (0.6 ml/min). Detection was performed using a flow-through all-solid-state ammonium ISE with a double-junction Ag/AgCl electrode as reference connected to a potentiometer and a recorder. The calibration graph was linear from 0.3-30 mM urea and the RSD (n = 30) was 0.8%. Results are discussed. An analytical system specially built for online urea monitoring is reported. Measurements are carried out in the effluent of a haemodialysis machine. The measuring system employs the dialyser inflow stream as a carrier solution channel in a continuous fashion. The analyzer. periodically samples the outflow stream of the dialyser by means of an automatic injection valve. The analyzer. features a bioreactor consisting of immobilized urease and a gas diffusion module. It is through this module that the urea is converted to ammonia gas which is transferred to another carrier channel, this transports the ammonium ion to a tubular, all-solid-state, ion-sensitive electrode. A timer controls the transport, injection, the measuring and the recording subsystems. The analyzer. has been used during actual haemodialysis sessions. Urea clearances were also measured in batch, using conventional spectrophotometric clinical equipment. The correlation between both methodologies was sufficient to confirm the usefulness of the developed online analyzer. to monitor the optimal length of haemodialysis sessions.
Urea Blood Potentiometry Sensor

"Flow Injection Determination Of Total Ammonia And Total Carbon Dioxide In Blood Based On Gas-diffusion Separation And With A Bulk Acoustic Wave Impedance Sensor"
J. Pharm. Biomed. Anal. 1998 Volume 16, Issue 5 Pages 759-769
Xiao-Li Su, Bing-sheng Yu, Hu-wei Tan, Xiao-rong Yang, Li-hua Nie and Shou-zhuo Yao*

Abstract: A novel flow injection (FIA) system, for the rapid and direct determination of both total NH3 (TNH3) and total CO2 (TCO2) in clinical blood samples, was developed. Samples were injected into a carrier stream of water, then emerged with a reagent stream, where the analyte was converted into a gaseous species and diffused across a PTFE gas-permeable membrane into an acceptor stream. The trapped NH3/CO2 in the acceptor was determined on line by a bulk acoustic wave (BAW) impedance sensor. At a through-put of 20 and 65 h-1, the proposed system exhibited a linear frequency response up to 200 µmol L-1 ammonium and 20 mmol L-1 bicarbonate with a detection limit of 1.0 and 10 µmol L-1, respectively. Results obtained for TNH3 in serum and TCO2 in plasma were in agreement with those obtained by the conventional glutamate dehydrogenase (GDH) method and gas-sensing electrode method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rate and potential interferents on the FIA signals are also discussed.
Ammonia, total Carbon dioxide Blood Plasma Blood Serum Conductometry Sensor

"Novel Chemiluminometric H2O2 Sensors For The Selective Flow Injection Analysis"
Sens. Actuat. B 1998 Volume 51, Issue 1-3 Pages 107-113
D. Janasek*, U. Spohn and D. Beckmann

Abstract: H2O2 can be detected chemiluminometrically in the presence of luminol at Co and Cu foils. The chemiluminescence signal can also be induced electrochemistry. The linear determination ranges are 0.1-200 µM on Co and 5-2000 µM on Cu under flow injection conditions. To improve the selectivity the chemiluminescence detector was combined with a thin layer gas dialysis cell. H2O2 was detected at 0.5-100 mM. The interference by a >100-fold excess of EDTA, α-ketocarboxylic acids and peroxodisulfate can be excluded. Peroxomonosulfate concentrations greater than a 10-fold excess of H2O2 cause a significant bias, which resulted from the hydrolysis of peroxomonosulfate.
Hydrogen peroxide Chemiluminescence Chemiluminescence Sensor Sensor

"Potentiometric Determination Of Ethanol In Alcoholic Beverages Using A Flow Injection Analysis System Equipped With A Gas Diffusion Unit With A Microporous Poly(tetrafluoriethylene) Membrane"
Anal. Sci. 1990 Volume 6, Issue 4 Pages 541-546
H. OHURA, T. IMATO, Y. ASANO, S. YAMASAKI and N. ISHIBASHI

Abstract: The method involves the oxidation with K2Cr2O7 of ethanol permeating through a porous membrane, the reduction of unconsumed Cr2O72- with Fe2+ in a flow injection system, and the determination of the Fe3+ produced with a redox electrode. A diagram is presented of the flow injection manifold equipped with a gas diffusion separation unit. Results agreed with those obtained by a specific gravity method and by GC. The method is useful for application to alcoholic beverages owing to its high selectivity, high throughput, low cost and simplicity of operation.
Ethanol Beer Wine Sake Shochu Whisky Potentiometry GC

"Flow Injection Analysis For The Determination Of Urea In Cows Milk"
Acta Vet. Scand. 1985 Volume 26, Issue 3 Pages 396-404
Oltner R, Bengtsson S, Larsson K.

Abstract: An inexpensive and easily automated flow injection method for determination of urea in cow's milk was evaluated. Urea is hydrolyzed by urease and in a gas diffusion cell the ammonia formed passes a membrane into an indicator solution. The resulting color change of the indicator is measured at 590 nm. The repeatability of the analysis, expressed as the coefficient of variation (C.V.), was between 0.5 and 1.2%. Measured (y) and expected (x) milk urea concentrations after addition of known amounts of urea were related according to the equation y = 1.00x - 0.12 with a C.V. for the regression of 1.8%. Recommended amounts (0.02%) of the preservative bronopol (2-bromo-2-nitropropane-1,3-diol) added to the milk did not affect the results (P > 0.05).
Urea Cows Milk Spectrophotometry

"High Speed, On-stream Acid-base Titration Utilizing Flow Injection Analysis"
Adv. Instrum. 1984 Volume 39, Issue 1 Pages 279-285
NA (Karl D. Schick)

Abstract: Single point titration by flow injection analysis (FIA) allows rapid, on-stream determination of acids and bases. A small volume of acid or base is injected into a linear buffer, the resulting local pH change in the flowing buffer stream is linearly related to the concentration. of the injected acid or base. Process applications dealing with the determination of H2SO4 (1-10%), caustic (0.1-10%) and NH3 (1-6%) are discussed. A simple, on-stream sample clean-up procedure and device is also described. (SFS)
Ammonia pH Potentiometry Spectrophotometry

"Gas Diffusion/flow Injection Analysis: Applications And Trends"
Analusis 1988 Volume 16, Issue 4 Pages 216-220
Lazaro, F.;Luque De Castro, M.D.

Abstract: A review is presented, with 28 references, of the principles and features of the cited techniques. The various applications and analytical parameters are tabulated.

"Automated Tobacco Analysis By Means Of Flow Injection Analysis"
Beitr. Tabakforsch. Int. 1988 Volume 14, Issue 2 Pages 105-118
Finster P, Hollweg J, Kausch E, Burmester U

Abstract: The construction and mode of operation are described of a simple modular instrument for flow injection analysis. The instrument, which is suitable for multi-component analysis of small series of samples, was applied in determination of nicotine, NO3-, Cl-, NH4+ and PO43- in tobacco. Stopped-flow conditions permitted removal of background absorbance originating from the sample matrix.
Nicotine Nitrate Chloride Ammonium Phosphate Plant Sample preparation

"Flow Injection Analysis With Membrane Separation. Determination Of Ammonia In Blood And Urine"
Bunseki Kagaku 1984 Volume 33, Issue 10 Pages 505-509
Aoki, T.;Uemura, S.;Munemori, M.

Abstract: The sample, made alkaline with 1 M NaOH, was injected into the outer tube of a separation unit (shown diagrammatically), which comprised an inner micro-porous PTFE tube containing phthalaldehyde - 2-mercaptoethanol reagent, and an outer tube containing water. Ammonia permeated into the inner tube and the reaction product flowed into a flow cell for fluorimetric determination at 486 nm (370-nm excitation). Calibration graphs were rectilinear for 1 µM to ~1 mM NH3. Various compounds commonly found in blood and urine did not interfere. Recovery of NH3 was 95 to 108, 104 to 110 and 97 to 101% from whole blood, plasma and urine, respectively.
Ammonia Whole Blood Plasma Urine Clinical analysis Fluorescence

"Determination Of Total Nitrogen In Waters By A Continuous-flow Method Involving Alkaline Peroxodisulfate Digestion"
Bunseki Kagaku 1986 Volume 35, Issue 1 Pages 32-37
Aoki, T.;Uemura, S.;Munemori, M.

Abstract: Water (at 2 mL min-1) is continuously mixed with 0.1 M K2S2O8 (6 M in NaOH and plus 0.1% of Se), at a flow rate of 1.5 mL min-1, and the mixture is heated in a reaction coil (80 cm x 1.5 mm) at 175°C. After cooling in an ice bath, the reaction mixture is passed to a debubbler and mixed with 4% TiCl3 solution (0.7 mL min-1), thereby reducing NO3- to NH3, which is passed to a double-tube separation unit. The NH3 in the outer tube passes through a micro-porous PTFE membrane into the inner tube, through which phthalaldehyde reagent is passed (0.3 mL min-1), and the fluorescence of the emergent solution is measured at 486 nm (excitation at 370 nm). The response (obtained in <10 min) is rectilinearly related to concentration. of N from 0.02 to 10 mg l-1, the detection limit is 9 µg l-1, and the coefficient of variation at the 0.2 mg L-1 level is 2.5% (n = 4). There is no interference from coexisting inorganic salts.
Nitrogen, total Water Fluorescence Sample preparation

"Determination Of Ammonia Nitrogen In Water By Flow Injection Analysis With A Gas Diffusion Unit"
Bunseki Kagaku 1987 Volume 36, Issue 8 Pages T81-T84
Kuwaki, T.;Akiba, M.;Oshima, M.;Motomizu, S.

Abstract: A gas diffusion unit containing a tubular micro-porous PTFE membrane is described and its application in the determination of ammonia-N in water is studied. The sample is injected into an alkaline stream where the NH4+ is converted into NH3. The carrier stream then flows into the gas diffusion unit containing reagent solution (thymol blue adjusted to pH 8.4) and the NH3 passes through the PTFE membrane and reacts with the thymol blue. The color change is measured at 596 nm in a flow-through cell. The detection limit is ~2 ppb and response is rectilinear up to 5 ppm. The sampling rate is 25 h-1 and the coefficient of variation is 3.8 and 1.6% for 20 and 200 ppb, respectively. Results obtained by direct injection agree well with those obtained by injecting solution prepared according to the micro-Kjeldahl distillation method.
Ammonia, nitrogen Environmental Spectrophotometry

"Determination Of Total Carbonate-carbon In Water By Flow Injection Analysis With A Gas Diffusion Unit"
Bunseki Kagaku 1987 Volume 36, Issue 12 Pages T132-T135
Kuwaki, T.;Toei, K.;Akiba, M.;Oshima, M.;Motomizu, S.

Abstract: Water samples were injected into a carrier stream of 1.8 mM H2SO4 and the CO32- and HCO3- were converted into gaseous CO2. This stream and the reagent stream (0.125 mM cresol red - 3 mM NaHCO3; pH 9.0) were fed into the gas diffusion unit. The CO2 passed through the PTFE membrane and the absorbance of the recipient solution was measured at 410 nm in a flow-through cell. The detection limit was 5 µM-CO32- and response was rectilinear up to 1.2 mM CO32-. The coefficient of variation (n = 10) for 0.47 mM CO32- was 0.8%. The sampling rate was 15 h-1. Results agreed well with those obtained by indirect ion chromatography - spectrophotometry.
Carbonate Environmental Spectrophotometry

"Determination Of Ethanol In Alcoholic Beverages By Gas Diffusion/flow Injection Analysis"
Bunseki Kagaku 1988 Volume 37, Issue 10 Pages T105-T108
Imato, T.;Ohura, H.;Asano, Y.;Yamasaki, S.;Ishibashi, N.

Abstract: The method involved use of a gas diffusion unit (illustrated), equipped with a poly(substituted acetylene) - polysiloxane copolymer membrane. Sample solution (140 µL) was injected into a carrier water stream, which was passed through one compartment of the gas diffusion unit at 70°C. Ethanol(I) diffused across the membrane, where it was absorbed by a carrier stream of water. This stream was mixed successively with ones of K2Cr2O7 solution, at 70°C, and of Fe(II) solution, and Fe(III) formed was determined by measurement of peak potential. Peak height was rectilinearly related to I concentration. in the range 5 to 30%. In the determination of 16% of I, the coefficient of variation (n = 6) was 1.9%. Sugars, amino-acids and carboxylic acids did not interfere. The method was applied in the analysis of sake, shochu and whisky.
Ethanol Sake Shochu Whisky Potentiometry

"Assembly Of A New Gas Diffusion Unit And Its Application To The Determination Of Total Carbonate And Ammoniacal Nitrogen By FIA"
Bunseki Kagaku 1993 Volume 42, Issue 9 Pages T123-T128
Sanada, M.;Oshima, M.;Motomizu, S.

Abstract: A gas diffusion unit was developed (diagrams given) and used in the flow injection spectrophotometric determination of ammonia-N or carbonate in natual waters. The unit consisted of an inner microporous PTFE tube (pore size 0.2 µm) and an outer PTFE tube. Sample was injected into a carrier stream, where the analyte was converted into a gaseous species and passed through the inner PTFE tube into the reagent stream, which flowed between the outer and inner tubes. The change in pH caused the color of the reagent stream to alter, which was detected spectrophotometrically. For the ammonia-N determination, the carrier stream was 0.02 M NaOH, the reagent stream contained 0.125 mM Cresol Red of pH 7 (details given) and the absorbance was monitored at 550 nm. For the determination of carbonate, the carrier stream was 1.8 mM H2SO4, the reagent stream contained 0.125 mM Cresol Red of pH 9 (details given) and absorbance was measured at 410 nm. The detection limits for ammonia-N and carbonate, respectively, were 0.03 and 0.96 mg/l; the corresponding calibration graphs were linear up to 3.5 and 172 mg/l. Sampling rates were 30 and 20 per h, respectively. The method was applied to river and seawater.
Carbonate Ammonia, nitrogen River Sea Spectrophotometry

"Simple And Rapid Determination Of Micro Amounts Of Nitrogen In Steel By An FIA Method Involving Gas Diffusion Separation And Spectrophotometric Detection"
Bunseki Kagaku 1995 Volume 44, Issue 9 Pages 725-730
Komoda, M.;Ono, A.;Kaneko, S.;Yamane, T.

Abstract: A steel sample is dissolved in HCl, and 1.4 mL of the solution is injected into a carrier stream of water (0.2 ml/min) that then merges with a stream of aqueous 15% tartaric acid/5 M NaOH (0.2 ml/min). The evolved NH3 diffuses through porous PTFE membrane tubing into a stream of aqueous NaClO (0.05% of available Cl)/0.2 M NaOH (0.4 ml/min) in the inner channel that then merges with a stream of 0.5% 1-naphthol solution in aqueous 35% acetone (0.4 ml/min). After passage of the combined streams through a 5 m reaction coil the absorbance is measured at 732 nm. The calibration graph is linear for up to 0.5 µg/ml of N, and down to 2 µg/g in the sample can be determined. Results for reference steels agreed with the certified values, and results for carbon steels agreed with those obtained by the Japanese industrial standard method.
Nitrogen Alloy Spectrophotometry

"Determination Of Trace Amounts Of Nitrogen In Steel By Gas Diffusion/flow Injection Waveguide Capillary-cell Spectrophotometry"
Bunseki Kagaku 1996 Volume 45, Issue 2 Pages 193-199
Aimoto, M.;Komoda, M.;Chiba, K.

Abstract: A steel sample is dissolved in HCl, and 0.5 mL of the solution is injected into a carrier stream of water, which subsequently merges with a stream of 15% tartaric acid solution in 6 M NaOH (both 0.4 ml/min). The combined streams pass through a reaction coil (100 cm x 0.5 mm i.d.) to a 30 cm long gas-liquid-separator, and the NH3 diffuses into a stream of NaClO solution (0.05% of available Cl) in 0.2 M NaOH, which subsequently merges with a stream of 0.5% 1-naphthol solution in aqueous 45% acetone (both 0.3 ml/min). Finally, the combined streams pass through a reaction coil (300 cm x 0.5 mm i.d.) to a waveguide capillary cell (50 cm x 0.68 mm i.d., 1.18 mm o.d.) for absorption measurement at 732 nm. Light from a Xe lamp is selected by a monochromator, focused by a lens, and conducted to the waveguide capillary cell and thence to a photomultiplier tube by optical fibers. The calibration graph is linear for up to ~e;500 ng/ml of N in the sample solution (50 µg/g in the steel). The RSD (n = 3) for 2 µg/g of N was ~e;3%, the results for four certified reference materials agreed with the certified values, and the results for two steels agreed with those obtained by the JIS standard method.
Nitrogen Alloy Sample preparation Spectrophotometry

"Gas Diffusion Flow Injection Analysis Applied To The Determination Of Sulfite And Sulfur Dioxide In Environmental Samples"
Chem. Anal. 1995 Volume 40, Issue 4 Pages 619-630
Frenzel, W.;Hillmann, B.

Abstract: To determine free sulfite, sample (300 µL) was injected into a carrier stream (1.2 ml/min) of water which merged with a stream (0.8 ml/min) of 0.2 M H2SO4 and passed through a reaction coil (60 cm x 0.7 mm i.d.). The SO2 produced was transferred to a stream (0.6 ml/min) of color reagent (50 mg 4,4'-dithiodipyridine, 10 mL ethanol and 1.02 g potassium hydrogen phthalate diluted to 250 mL with H2O) in a gas diffusion unit. It then passed through a reactor (45 cm x 0.7 mm i.d.) and the absorbance was measured at 324 nm. To determine gaseous SO2 collected in formaldehyde solution, samples (500 µL) were injected into a H2 carrier and treated with 0.45 M NaOH prior to acidification and release of SO2 (FIA manifold shown). The calibration graphs were linear for 0.25-10 and 0.5-20 mg/l free and bound sulfite, respectively, and the detection limits were 0.08 and 0.15 mg/l, respectively. The RSD were 1-3% and the sampling frequency was 20-30/h. Interferences were investigated. The methods were applied to the determination of sulfite in tap, surface and waste waters and brine, and to the determinations of SO2 in air (details given).
Sulfite Sulfur dioxide Environmental Environmental Water Surface Waste Spectrophotometry

"A Computational Technique For Simulating The Dynamic Response Of A Flow Injection Analysis System"
Chem. Eng. Sci. 1992 Volume 47, Issue 7 Pages 1591-1600
Steven H. Isaacs and Henrik Soeberg, Lars H. Christensen and John Villadsen

Abstract: A computational technique is presented for obtaining the dynamic response to a gas diffusion module as part of a flow injection analysis (FIA) system. Based on orthogonal collocation, Laplace transformation, and Fourier series, the method provides a relatively quick way to account for dispersive effects occurring via longitudinal convection and lateral diffusion. Simulation examples, including a comparison with a dynamic signal obtained with an actual FIA system, are provided.

"Comparison Of Methods In Analytical Practice. 2. Determination Of Ammonium In Water"
Chem. Labor Betr. 1997 Volume 48, Issue 1 Pages 12-14
Schwedt, G.;Laue, D.

Abstract: A comparison is made between spectrophotometry based on the indophenol reaction, direct potentiometry with a polymer-based ion-selective electrode, and FIA with diffusion of NH3 into a mixed indicator for the determination of NH4+. Apparatus and procedures used, limits of detection and determination, linear ranges, analysis times and other performance criteria are tabulated. Spectrophotometry is the most sensitive method, potentiometry has the widest range of measurement, and FIA is the most suitable for automation.
Ammonium Water Spectrophotometry Potentiometry Electrode

"Online Sample Preparation With Flow Injection Analysis: Avoiding Additional Preparation Steps"
Chem. Rundsch. 1987 Volume 40, Issue 11 Pages 11-NA
Winter, B.

Abstract: As illustrated by the determination of NH4+ and of surfactants, it is shown that single stages or the entire sample preparation can be integrated by use of flow injection analysis. Problems of the matrix in determining NH4+ in, e.g., waste water, soil extracts or acid digests of food are discussed; the NH4+ can be separated from the matrix by gas diffusion from NaOH medium into a receptor stream for photometric detection. Surfactants can be separated from environmental, food or pharmaceutical samples by liquid - liquid ion-pair extraction into CHCl3, with use of a PTFE membrane as phase separator and photometric detection. Flow diagrams for these analyzes are presented.
Ammonium Surfactants Food Pharmaceutical Environmental Waste Sample preparation Spectrophotometry

"Determination Of Total Carbon Dioxide In Plasma By Automated Flow Injection Analysis"
Clin. Chem. 1979 Volume 25, Issue 3 Pages 443-445
H Baadenhuijsen and HE Seuren-Jacobs

Abstract: A procedure for measuring total CO2 in plasma is described. It is based on the principles of the flow injection analysis technique which makes use of unsegmented fast-flowing reagent streams as developed by Ruzicka et al. The further methodological design resembles the silicone-rubber membrane technique of Kenny and Cheng. CO2 in the sample is released by reaction with H2SO4. Appropriate amounts of CO2 permeate through the membrane that separates the acid reagent stream and a buffered cresol-red indicator stream. The experimental set-up and functioning of this system are described. A procedure is described for measuring total CO2 in blood plasma by the flow injection analysis technique, which uses unsegmented fast-flowing reagent streams, as developed by J. Ruzicka, et al. (1975). CO2 in the sample is released by reaction with H2SO4. Appropriate amounts of CO2 permeate the membrane that seps. the acid reagent stream and a buffered cresol red indicator stream. The experimental setup and functioning of this system are described.
Carbon dioxide Blood Plasma Clinical analysis Spectrophotometry

"Flow Injection Analysis With Chemiluminescence Detection"
Clin. Chem. 1979 Volume 25, Issue 9 Pages 1635-1638
G Rule and WR Seitz

Abstract: In 'flow injection analysis', the sample is inserted into a stream of reagent by use of a sample-injection valve. Mixing occurs downstream from the valve in a coil of tubing. With chemiluminescence detection this coil is positioned in front of a photomultiplier. We have evaluated the system for detection of hydrogen peroxide, using the luminol reaction with cupric ion as a catalyst. The effects of flow rate, sample volume, and reaction kinetics on the magnitude, duration, and repeatability of the chemiluminescent response have been evaluated. Precisions of 1 to 2% relative standard deviation on replicate measurements are readily achievable. A sample throughput of six samples per minute is possible with very little peak overlap. This detection system can be coupled to any process in which peroxide is generated.
Hydrogen peroxide Clinical analysis Chemiluminescence

"Rapid Determination Of Ammonia In Whole Blood And Plasma Using Flow Injection Analysis"
Clin. Chim. Acta 1982 Volume 119, Issue 1-2 Pages 7-14
Gunilla Svensson* and Torbj&ouml;rn Anf&auml;lt

Abstract: A flow injection method for the determination of ammonia in whole blood and plasma is described. The method utilizes diffusion of ammonia into a stream of a pH-sensitive indicator, which is monitored by a photometer. A volume of 90 µL is needed and the result is obtained within 1 min. Ammonia concentrations increase during storage due to deamination. It is proposed to use plasma samples, which could be stored frozen at -20°C without significant change.
Ammonia Whole Blood Plasma Clinical analysis Spectrophotometry

"Conductimetric Gas Separation-flow Injection Determination Of Ammonia In Gaseous Process Streams"
Collect. Czech. Chem. Commun. 1997 Volume 62, Issue 4 Pages 609-619
Vlastimil KUBAN

Abstract: The membrane separation technique is employed for a selective determination of ammonia in gaseous samples. The gases and purified air were sampled into the outer part of a membrane device with poly(vinylidene difluoride) microporous membranes (0.56 µm pore size, 1.2 mm i.d., active length 2 or 10 cm), with acceptor streams flowing inside the membrane in the continuous-flow mode. The ammonium ions were fed directly into the conductivity detector of the FIA manifold. The dependence of the analytical signal on the initial conductivity of the acceptor streams containing HNO3 is graphically presented. Calibration graphs were non-linear for water, strong acids, and barbituric acid over concentrations 0-1 vol% ammonia in N3, but they were linear for 3 mM boric acid.
Ammonia Gas Environmental Conductometry

"Gas Diffusion-flow Injection Determination Of Free And Total Sulfur Dioxide In Wines By Conductometry"
Collect. Czech. Chem. Commun. 1998 Volume 63, Issue 6 Pages 770-782
Petr KUBAN, Pavel JANOS and Vlastimil KUBAN

Abstract: Sensitive flow injection analysis methods for the determination of free and total sulfur dioxide in wines are presented. The bound S(IV) was liberated by alkaline hydrolysis with 4 mol/l NaOH. All forms of S(IV) were liberated from the sample zone by sulfuric acid and subsequently transported through a microporous PVDF membrane. The penetrated gases were collected in water for preselected period and determined by conductometry with detection limit 1 mg/l and relative standard deviations 0.8 and 0.6% at 10 and 150 mg/l (n = 10) for free and total S(IV), respectively. The results are comparable with those obtained by standard titrimetric procedures with visual (Czech State Standard) and/or potentiometric indication.
Sulfur dioxide Wine White Conductometry

"Gas Diffusion - Permeation Flow Injection Analysis. 1. Principles And Instrumentation"
Crit. Rev. Anal. Chem. 1992 Volume 23, Issue 5 Pages 323-354
Vlastimil Kub&aacute;n

Abstract: A review is presented, with 109 references, of the application of gas diffusion - permeation flow injection analysis (GDP FIA) in the separation and/or pre-concentration. of gases, gas-evolving species and volatile inorganic and organic substances. Principles of the technique and factors influencing transmembrane transport are described. Different configurations of FIA manifolds for stopped-flow, closed-loop and continuous-flow arrangements are discussed, as are designs for principal instrumental modules, characteristics of different semi-permeable membranes and special arrangements of detection systems. A review with 109 references. Gas diffusion/permeation techniques involving different membrane interphases or an open fluid/fluid interface are presented as powerful tools for separation and/or pre-concentration of a variety of classes of analytes, i.e., gases, gas-evolving species, volatile inorganic and organic substances, etc., from gaseous, aquatic, or organic sample matrixes. Principles of the techniques and factors influencing transmembrane transport, such as acidity of the donor and the acceptor streams, their flow rates, membrane characteristics, temp., pressure, etc., are described. Different configurations of flow injection analysis manifolds for stopped-flow, closed-loop, and continuous-flow arrangements, designs of principal instrumental modules, characteristics of different semipermeable membranes, and special arrangements of detection systems are outlined.

"Determination Of Ammonium And L-glutamine In Hybridoma Cell Cultures By Sequential Flow Injection Analysis"
Cytotechnology 1994 Volume 14, Issue 3 Pages 177-182
Carles Campmaj&oacute;, Jordi Joan Cair&oacute;, Anna Sanfeliu, Esteve Mart&iacute;nez, Salvador Alegret and Francesc G&oagrave;dia

Abstract: A flow injection analytical system based on a gas diffusion membrane module for ammonia and an ammonium flow-through potentiometric detector has been set up for measurement of L-glutamine and ammonium ions in hybridoma cell cultures. The main feature of the system is that the same basic analytical concept and equipment is used in both measurements, the only difference being for the determination of L- glutamine, in which the sample flows through an immobilized glutaminase cartridge. The conditions to enable the performance of both analysis consecutively, avoiding potential interferences by unwanted deamination of other compounds in the samples, have been determined. Finally, the proposed system has been compared with reference analytical methods for batch hybridoma cell culture experiments.
Ammonium l-Glutamine Fermentation broth Potentiometry

"FIA System With Urease Reactor For The Determination Of Urea In Food"
Dtsch. Lebensm. Rundsch. 1994 Volume 90, Issue 6 Pages 178-181
Schwedt, G.;Shi, R.;Stein, K.

Abstract: Urease, immobilized on 150 mg of VA Epoxy resin (Riedel-de Haen), was packed in a glass column (4.5 cm x 2 mm i.d.), which was mounted in a flow injection system. Meat, fish and milk were extracted with HClO4 or trichloroacetic acid, the extracts were neutralized and portions of the extract (0.1 ml) were injected into a carrier stream of water. After passing through the urease reactor the stream was mixed with alkaline EDTA solution. The mixture passed over a gas diffusion membrane, where the NH3 formed diffused into an absorber solution, which contained bromocresol violet, bromothymol blue and cresol red. The absorbance of the resulting solution was measured at 590 nm; linear calibration graphs for 50-800 ppm of urea were obtained. Regular calibration was required as the reactor lost 25% of its activity after 24 days storage at 60°C. Corrections were required for the ammonia content of some samples; these were obtained by allowing the sample to bypass the reactor. Results were similar to those obtained by the Boehringer UV test and by the official photometric method of the food industry.
Urea Meat Marine Cows Milk Spectrophotometry

"Biosensors In Automated Analysis Systems. 1. Determination Of Ethanol In Beer And Wine By Flow-diffusion Analysis And Amperometric Detection"
Dtsch. Lebensm. Rundsch. 1996 Volume 92, Issue 1 Pages 1-4
MOHNS J. ; K&Uuml;NNECKE W.

Abstract: The flow diffusion system employed (schematic given) included a thermostatted diffusion cell with a hydrophobic gas diffusion membrane, an enzyme reactor, and a thick-layer Pt electrode in a wall-jet flow cell. The ethanol was converted enzymatically to acetaldehyde and H2O2, and the H2O2 detected electrochemically at the Pt electrode at 700 mV. The enzyme was alcohol oxidase immobilized by the glutaraldehyde method on CPG 10 (controlled pore glass). Twenty alcohol-free beers, 16 beers and 13 wines were examined. The correlation between this method and the standard methods was very good (correlation coefficient of 0.9992). Thirty samples per hour could be analyzed and the flow analysis system had a linear range up to 15% v/v.
Ethanol Beer Wine Sensor Electrode Electrode Amperometry

"Biosensors In Automated Analysis Systems. 2. Fructose Determination In Juices By Fructose Dehydrogenase Thick-film Platinum Electrodes"
Dtsch. Lebensm. Rundsch. 1996 Volume 92, Issue 2 Pages 35-39
HANKE A. ; EBERHARDT A. ; BILITEWSKI U. ...

Abstract: Fructose was determined amperometrically with a ring-disc electrode of alumina ceramic coated with Pt paste containing immobilized fructose dehydrogenase and BSA. The Pt ring was the reference electrode and the injection needle was the counter electrode. The working electrode was fitted into a Plexiglas flow-through wall-jet cell. The system was used in FIA, flow diffusion analysis and HPLC. Fruit juice was diluted 1:100 (and filtered, for FIA or HPLC). For FIA, the sample was first passed through an ascorbate oxidase reactor to remove ascorbic acid. The FIA flow stream or flow diffusion acceptor stream was 0.15 M McIlvaine buffer of pH 5, containing 5 mM potassium ferricyanide as mediator and detection was at 390 mV. For HPLC, a 5 µm Supelcosil LC-18 column (25 cm x 4.6 mm i.d.) was used at 15°C with water as mobile phase (0.3 ml/min) and the eluate was mixed with 0.3 M McIlvaine buffer of pH 5, containing 10 mM potassium ferricyanide before detection at 390 mV. The HPLC method gave the best agreement of results on a range of juices with those of enzymatic analysis, but FIA gave better sample frequency.
Fructose Fruit Amperometry Electrode Electrode Sensor

"Flow Injection Analysis Of Cyanide In Wastewater From Metal Plating Process"
Eisei Kagaku 1984 Volume 30, Issue 1 Pages 7-13
CHIYOMI OKUMOTO, MACHIKO NAGASHIMA, SHIGERU MIZOIRI, MASAYOSHI KAZAMA, KAZUYUKI AKIYAMA

Abstract: The sample (at 1.2 mL min-1) was mixed with aqueous 2% H2SO4 (0.4 mL min-1) to adjust the pH to <2 and the solution was mixed with a carrier flow of aqueous 10% NaCl (2.0 mL min-1). The liberated HCN diffused via a PTFE membrane in a gas diffusion cell at 40°C into a stream of 0.1 M NaOH (1.2 mL min-1), and this collector stream was monitored with a CN--selective electrode. By use of a calculated mean HCN permeability of 34% at 1 µg mL-1, a rectilinear calibration graph was obtained in the range 0.3 to 100 µg mL-1 of CN-. Forty samples could be analyzed in 1 h.
Cyanide Waste Electrode

"Continuous-flow Method For Simultaneous Determination Of Nitrate And Ammonia In Water"
Environ. Sci. Technol. 1986 Volume 20, Issue 5 Pages 515-517
Toyoaki Aoki, Satoshi Uemura, and Makoto Munemori

Abstract: River water was analyzed by continuous-flow analysis. The sample was mixed with 0.3% sulfanilic acid solution, 7 M NaOH and TiCl3 solution, and the NH3 present in the sample or produced by the reduction of NO3- permeated through a micro-porous PTFE membrane into a buffer solution containing phthalaldehyde - 2-mercaptoethanol. The fluorescence of the buffer solution was then measured at 486 nm (excitation at 370 nm); the original NH3 content was determined as above but without the reduction of the NO3-. The calibration graphs for NO3- and NH3 were rectilinear for 0.5 µM to 0.2 mM and 0.2 µM to 0.2 mM, respectively, and the corresponding detection limits were 0.18 µM and 0.018 µM. The coefficient of variation were 3.3 and 4.4% for NO3- and NH3, respectively. Interference due to methylamine and ethylamine was reduced by lowering the pH of the reaction solution
Ammonia Nitrate River Fluorescence

"Rapid Distillationless 'Free Cyanide' Determination By A Flow Injection Ligand Exchange Method"
Environ. Sci. Technol. 1995 Volume 29, Issue 2 Pages 426-430
Emil B. Milosavljevic, Ljiljana Solujic, and James L. Hendrix

Abstract: Sample solution was injected into a carrier solution (1 ml/min) of 0.2 M HCl. the carrier stream merged with a reagent stream (1 ml/min) of 0.2 M HCl, passed through a mixing coil (30 cm x 0.5 mm i.d.) and into a diffusion cell with an acceptor solution 92 ml/min) of 0.01 M NaOH. The resulting solution went into a thin layer flow-through amperometric cell comprising a Ag working and Pt counter electrode with a Ag/AgCl reference electrode separated from the flowing stream by an ion exchange Nafion membrane. The cell was potentiostated and the current measured by a pulsed amperometric detector. The dynamic range of the FIA system was 0.001-5 µg/ml and recoveries of cyanide from all metal cyano complexes that produce free cyanides were 97.4-104.3% with RSD of 0.2-1.3% for 0.2 µg/ml cyanide and 98-103% with RSD of 0.2-0.7% for 2 µ/ml cyanide. The method was used to determine cyanide in industrial process waters. In the first part of this research, extensive species-dependent cyanide recoveries studies were performed using the approved standard methods available for determination of free cyanide. The data obtained show that serious problems are associated with both the CATC (cyanide amenable to chlorination) and WAD (weak and dissociable cyanide) methods. In the second part, a novel flow injection gas diffusion method for the determination of free cyanide was developed. Complete cyanide recoveries even in the presence of a large excess of the free CN- ion were found for the following species: 2-, 2-, 2-, 3-, -, 2-, and Hg(CN)2. No recoveries of CN- were obtained from the species that are considered as non free cyanide producing ones, such as 3-/4-, 3-, and -. The method developed is rapid, selective, reproducible, and easy to automate. Copyright 1995, American Chemical Society.
Cyanide, free Water Amperometry Electrode

"Determination Of Organically Bound Sulfur In Swamp And Terrestrial Waters By Continuous-flow Oxidation And Ion Chromatography"
Environ. Sci. Technol. 1995 Volume 29, Issue 4 Pages 849-855
Joan Crowther, Francis B. Lo, Michael W. Rawlings, and Bernard Wright

Abstract: Swamp or lake water (1 ml/min) was mixed with air (0.32 ml/min) and 10% H2O2 and the stream passed into a UV digester containing a 50 turn 1.5 mm i.d. quartz coil. A flow rate of 2 ml/min allowed a 3.5 min exposure time. CO2 produced was released by passing through a porous PTFE tube (12 cm x 2 mm i.d.). The digested sample stream was spiked with 30 mM NaHCO3 and 24 mM Na2CO3 (0.1 ml/min) and then analyzed by ion chromatography on two columns (no dimensions given) of HPIC-AG3 with a HPIC-AG1 guard column (no dimensions given), 3 mM NaHCO3 and 2.4 mM Na2CO3 as mobile phase (2.5 ml/min). The eluate passed into an anion micromembrane suppressor with 12.5 mM H2SO4 as regenerant (4 ml/min) for detection by conductivity. The calibration graph was linear for 0.2-10 mg/l sulfate with a detection limit of 0.05 mg/l. The RSD improves as the sulfate concentration increases.
Sulfur, organically bound Lake Swamp HPIC Conductometry

"Method Comparison And Evaluation For The Analysis Of Weak Acid-dissociable Cyanide"
Environ. Sci. Technol. 1997 Volume 31, Issue 1 Pages 52-57
John R. Sebroski and Richard H. Ode

Abstract: This study compared and evaluated three methods to determine weak acid-dissociable cyanide. An emphasis was placed on data quality using a performance-based approach to overcome the problems associated with cyanide analyzes. The three methods compared were Standard Methods, 18th ed., Method 4500 CN- l (macro distillation, colorimetric finish); Bayer Method SA-61A (steam distillation at pH 4.5, ion selective electrode finish); and Bayer Method SA-100 (FlA or flow injection analysis, gas diffusion separation, and amperometric detection). The study demonstrated method detection limits, recoveries of cyanide species, and use of ligand exchange reagents to improve selected cyanide species recoveries. Potential interferences were examined with the FIA procedure to demonstrate that the method would be applicable to industrial wastewater samples subject to NPDES regulations. This performance-based approach led to a successful means to measure weak acid-dissociable cyanide in an industrial effluent where other approved methods have failed.
Cyanide Water Waste Amperometry Electrode

"Determination Of Micro-amounts Of Sulfide Ion In Water By Flow Injection Analysis - Spectrophotometry With A Gas Diffusion Membrane"
Fenxi Huaxue 1992 Volume 20, Issue 7 Pages 844-846
Xu, H.H.;Chen, J.H.

Abstract: A gas diffusion membrane which can eliminate interferences in the cited determination is described (diagram given). Sample (190 µL) is injected into a 0.3 M H2SO4 carrier stream before diffusion of the H2S formed through the Teflon membrane to a reagent stream of acetic acid - Na acetate buffer (pH 3) containing 0.1% 1,10-phenanthroline, 1.2% ethanol and 12 mg of Fe(III). The absorbance of the complex formed was measured at 510 nm. The calibration graph was rectilinear from 0.25 (detection limit) to 25 µg mL-1 of S2-. At 15 µg mL-1 of S2- the coefficient of variation (n = 10) was 1% and recoveries were from 96 to 102%. Of ight foreign ions investigated, only SO32- interfered seriously. Sample throughput was 20 h-1.
Sulfide Environmental Spectrophotometry

"Spectrophotometric Determination Of Cyanide In Waste Water In A Flow Injection Analysis System With Gas Diffusion Separation"
Fenxi Huaxue 1993 Volume 21, Issue 4 Pages 449-451
Ma, H.C.;Liu, J.F.

Abstract: A sample of waste water (1.2 mL min-1) was mixed with 0.3 M HCl (0.6 mL min-1) in a flow injection manifold before entering through a gas diffusion separation set-up alongside a stream of 0.01 M NaOH (0.4 mL min-1), reacting with 0.5 M phospate buffer of pH 6.5 and 0.6% chloramine-I (0.4 mL min-1) then with 2% pyridine - barbituric acid (0.8 mL min-1) in a reaction tube and detection at 494 nm. The calibration graph was rectilinear for 0.1 to 18 µg mL-1 of cyanide; the detection limit was 0.02 µg mL-1. The sampling rate was 65 h-1.
Cyanide Waste Spectrophotometry

"Milk Acetone And Milk Urea As Markers Of Subclinical Disturbances In Dairy Herds"
FIAstar Newsletter 1986 Volume 5, Issue 1 Pages 1-NA
Andersson, L.

Abstract: NA
Acetone Urea Milk Spectrophotometry

"Application Of Flow Injection Analysis In Fruit Juice Analysis"
Fluess. Obst 1986 Volume 53, Issue 1 Pages 10-14
List, D.;Ruwisch, I.;Langhans, P.

Abstract: The principles and techniques of flow injection analysis are illustrated by means of phosphate and SO2 determinations in fruit juice. Phosphate is determined by use of ammonium molybdate followed by reduction of molybdophosphate to the molybdenum blue with SnCl2. The determination of SO2 is carried out at pH >7 to dissociate any compounds formed between SO2 and other components in the juice. The SO2 is then allowed to diffuse through a PTFE membrane into a gas diffusion cell where it is treated with p-rosaniline - formaldehyde, and the resulting color change is measured at 580 nm. Possible applications for flow injection determination of other substances, e.g., ascorbic acid, Cl-, glucose, hesperidin, Mg, Ca, lactic acid, NO2-, NO3-, D-sorbitol, SO42-, ethanol and NH3-N, are tabulated. Analyses were carried out with a microprocessor-controlled flow injection analyzer. type 5020 (Tecator).
Phosphate Sulfur dioxide Fruit Spectrophotometry

"Cold Vapor Atomic Absorption Determination Of Mercury In Soil And Plants Using A Flow Injection Gas Diffusion System"
Guangpuxue Yu Guangpu Fenxi 1987 Volume 7, Issue 1 Pages 57-61
Zhang, S.;Fang, Z.L.;Sun, J.

Abstract: Samples of soil and plants were analyzed for Hg by using the method of De Andrade et al. (Anal. Abstr., 1984, 46, 4B69) with modifications to improve the detection limit and sampling frequency, and to increase the lifetime of the PTFE membrane. The method involved permeation of Hg vapor through a PTFE membrane, which separated the flow cell from the optical path of the Nippon Jarrell Ash spectrometer. Absorption was measured at 253.7 nm. The detection limit was 0.06 µg L-1 of Hg, the sampling frequency was 200 h-1 and the coefficient of variation was 1% (n = 22) for 4 µg L-1 of Hg.
Mercury Plant Environmental Spectrophotometry

"Applications Based On Gas Diffusion And Flow Injection Analysis"
InFocus 1983 Volume 6, Issue 1 Pages 14-NA
Karlberg, B.;Twengstrom, S.

Abstract: NA
Ammonia Carbon dioxide Water Spectrophotometry

"Enzymatic Determination Of Dimethylformamide In Wastewater Using Flow Injection Analysis"
Int. J. Environ. Anal. Chem. 1988 Volume 33, Issue 2 Pages 131-139
Ludi, H.;Garn, M.;Ghisalba, O.;Schar, H.

Abstract: Waste water was diluted with 67 mM phosphate buffer of pH 7.0, and the solution (0.1 ml) was injected into the carrier stream (0.32 mL min-1) of 67 mM phosphate buffer (pH 7.0) and passed through an enzyme reactor containing immobilized NN-dimethylformamidase (cf. Schaer et al., Eur. J. Biochem., 1986, 158, 469). The DMF produced catalyzed the polymerization of 1,4-benzoquinone in another stream of the flow injection system, and detection of the polymer was at 500 nm. The calibration graph covered the range up to 15 mM DMF; the detection limit was 0.05 mM. Results generally agreed well with those obtained by GC.
Dimethylformamide Waste Spectrophotometry

"Simultaneous Continuous-flow Analysis Of Free And Total Sulfur Dioxide In Wine"
J. Agric. Food Chem. 1992 Volume 40, Issue 8 Pages 1355-1357
Fernando Falcone and Kenneth C. Maxwell

Abstract: Continuous-flow analysis of the cited compounds was conducted on a TRAACS 800 flow analyzer.. The method was based on the formation of a colored compound from reaction of the analyte, formaldehyde and p-rosaniline. The sample was introduced into the autosampler and split with half going to channel 1 (free SO2) and the other half to channel 2 (total SO2). For the determination of total SO2 the sample was first made basic with NaOH to liberate the bound SO2. Both samples were then acidified with H2SO4 to convert all forms of free SO2 to gaseous SO2, a portion of which diffused across a gas-permeable membrane into a stream of 1% H2SO4. The stream was mixed with formaldehyde and reacted with p-rosaniline. The complex was measured at 550 nm. The continuous-flow analysis was comparable to the Ripper method. Recoveries from sulfite-spiked wine samples ranged from 62 to 104% with an average precision of 4.5%.
Sulfur dioxide Wine Spectrophotometry

"Determination Of SO2 In Wines Using A Flow Injection Analysis System With Potentiometric Detection"
J. Agric. Food Chem. 1998 Volume 46, Issue 1 Pages 168-172
Alberto N. Ara&uacute;jo, Cristina M. C. M. Couto, Jos&eacute; L. F. C. Lima, and Maria C. B. S. M. Montenegro

Abstract: This paper describes the development and application of a flow injection analysis system manifold comprising a gas diffusion unit and a potentiometric detector to the determination of free and total SO2 in white and red wines. A homogeneous crystalline iodide double-membrane tubular electrode was used as detector. SO2 determination based on the Ripper method was carried out by dosing the iodide formed in the oxidation of SO2 with iodine, followed by the separation of the formed compound through a diffusion Teflon membrane. The results obtained from the analyzes of free and total SO2 in 30 wine samples showed good agreement between the proposed method and the rapid assay method recommended by the UE and OIV. The relative error deviations of the results obtained by both methods were <6%. This procedure is suitable for samples with ~3.2-180 mg L-1 SO2, performing determinations of 75-100 samples h-1.
Sulfur dioxide Wine Red Wine White Potentiometry Electrode Electrode

"Flow Injection System With Potentiometric Detection For The Determination Of Urea Content In Milks"
J. Agric. Food Chem. 1998 Volume 46, Issue 4 Pages 1386-1389
Jos&eacute; L. F. C. Lima, Cristina Delerue-Matos, and M. Carmo V. F. Vaz

Abstract: Two variant manifolds of a flow injection analysis (FIA) system are described for the determination of urea content in milks. This determination consists of the enzymatic reaction of urea with urease in which ammonium ion is formed. Ammonium is converted to ammonia by adding a NaOH solution and then led to a gas diffusion unit in which it diffuses to an acceptor channel (Tris/HCl, pH 7.5). Here, it is reconverted to ammonium ion and determined by a tubular configuration electrode sensitive to this ion. One of the FIA manifolds is based on the merging zones technique, whereas the other uses an immobilized enzyme. The results obtained were compared with those given by the Boehringer UV test and by the Official Method of Analysis of the Association of Official Analytical Chemists which can be applied to animal feed and adapted to the matrix studied. The relative deviation was less than 5%, and the precision of the developed methodologies considering RDS (%) was always less than 2%.
Urea Milk Feed Electrode Electrode Potentiometry

"Determination Of Sulfite In Food By Flow Injection Analysis"
J. AOAC Int. 1986 Volume 69, Issue 3 Pages 542-546
Sullivan JJ, Hollingworth TA, Wekell MM, Newton RT, Larose JE

Abstract: A method is described for the determination of sulfite levels in food products by flow injection analysis (FIA). The method is based on the decolorization of malachite green by SO2, which is isolated from the flowing sample stream by means of a gas diffusion cell. The FIA method has a detection limit in food sample extracts of 0.1 ppm SO2 (3 times peak height of blank), which corresponds to 1-10 ppm SO2 in a food product, depending on the extraction procedure used. At the 5 ppm SO2 level in a food extract, the precision of replicate injections is±1-2%. The method was tested on a variety of both sulfite-treated and untreated food products and the results compared favorably with those obtained by the Monier-Williams, colorimetric (pararosaniline), and enzymatic (sulfite oxidase) methods. The average differences from the FIA results were 19, 11, and 12%, respectively, for those samples (n = 12) above 50 ppm SO2. At lower levels the results were somewhat more erratic due to inaccuracies of the various methods at low concentrations. The method is based on the decolorization of malachite green (C. I. Basic Green 4) by SO2, which is isolated from the flowing sample stream by a gas diffusion cell; the decrease in absorbance is measured at 615 nm. The detection limit is 0.1 ppm, which corresponds to 1 to 10 ppm in a food product, depending on the extraction procedure used, which itself depends on the type of food being analyzed. For 5 ppm of SO2 in a food extract, the precision of replicate injections is ~1 to 2%. The proposed method was tested on sulfite-treated and untreated wine, apple juice, dried apricots, potatoes, pickled onions, shrimps, lettuce, dried apples and cabbage to give results in good agreement with those obtained by the Monier-Williams, pararosaniline colorimetric and sulfite oxidase methods. The mean differences from the proposed method were 19, 11 and 12%, respectively for the 12 samples with SO2 contents >50 ppm. At lower levels the results were somewhat more erratic. The construction of the flow injection apparatus is described in detail.
Sulfite Wine Juice Dried Vegetable Pickled Shrimp Vegetable Dried Vegetable Spectrophotometry Sample preparation

"Determination Of Total Sulfite In Shrimp, Potatoes, Dried Pineapple, And White Wine By Flow Injection Analysis: Collaborative Study"
J. AOAC Int. 1990 Volume 73, Issue 1 Pages 35-42
Sullivan JJ, Hollingworth TA, Wekell MM, Meo VA, Saba HH, Etemad-Moghadam A, Eklund C, Phillips JG, Gump BH

Abstract: A method for the determination of total sulfite in shrimp, potatoes, dried pineapple, and white wine by flow injection analysis (FIA) was collaboratively studied by 8 laboratories. In the method, the sample solution is reacted with sodium hydroxide to liberate aldehyde-bound sulfite. The sample stream is acidified to produce SO2 gas, which diffuses across a Teflon membrane in the gas diffusion cell into a flowing stream of malachite green. The degree of discoloration of the malachite green is proportional to the amount of sulfite in the sample solution. Red wine was included in the study but interlaboratory precision for these samples was not satisfactory and correlation with Monier-Williams results was poor. The present method is not recommended for use with these samples. For shrimp, potatoes, dried pineapple, and white wine, average reproducibility (RSDR) of results was 25% for samples at 10 ppm SO2 and 10% for samples at greater than 50 ppm. Overall average reproducibility was 14%. Recoveries of sulfite added to samples averaged 80%. Comparison of FIA with the Monier-Williams method indicated comparable results by the 2 methods. The FIA method has been adopted official first action for determination of greater than or equal to 5 ppm total sulfite in shrimp, potatoes, dried pineapple, and white wine.
Sulfite Shrimp Vegetable Dried Wine Red Wine White Spectrophotometry

"Determination Of Free (pH 2.2) Sulfite In Wines By Flow Injection Analysis: Collaborative Study"
J. AOAC Int. 1990 Volume 73, Issue 2 Pages 223-226
Sullivan, J.J.;Hollingworth, T.A.;Wekell, M.M.;Meo, V.A.;Etemad Moghadam, A.;Phillips, J.G.;Gump, B.H.

Abstract: A method for the determination of free sulfite in wine by flow injection analysis (FIA) is described. The method involves liberation of sulfur dioxide from the wine at pH 2.2, with detection by decolorization of a malachite green solution. The method was collaboratively studied, and the results indicated an average reproducibility of 12% for white wine samples (average level 12.1 ppm SO2) and 26% for red wine samples (average level 3.1 ppm). When the FIA method was compared to an aeration/oxidation method, the results indicated a high degree of correlation between the 2 methods. The FIA method has been adopted by AOAC official first action. Red or white wine was injected into a flow injection analysis (FIA) system and mixed with 0.5 M citric acid reagent (pH ~2). The SO2 produced diffused across a PTFE membrane in a gas diffusion cell into a flowing stream of malachite green solution. The degree of decolorization, which was proportional to the amount of SO2, was measured spectrophotometrically. Data from 7 laboratories indicated an average reproducibility of 12% for white wine (mean 12.2 ppm SO2) and 26% for red wine (mean 3.1 ppm). The results agreed with those from an aeration/oxidation method. It is recommended that the FIA method be adopted official first action, with the note that the method measures both free SO3-2 and any combined SO3-2 that is labile under the conditions used.
Sulfite Wine Red Wine White Spectrophotometry

"Amperometric Determination Of Nitrogen Dioxide In Air Samples By Flow Injection And Reaction At A Gas Liquid Interface"
J. Autom. Methods Manag. Chem. 1987 Volume 9, Issue 1 Pages 46-49
FRAZIER W. NYASULU and HORACIO A. MOTTOLA

Abstract: Air samples (245 µL) are injected into a stream of 1.0 M KCl containing 10 µM-tris-(1,10-phenanthroline)iron(II) (ferroin). Oxidation to ferriin takes place at the gas - solution interface; the solution passes through a mixing coil and is then debubbled via Gore-Tex PTFE tubing (pore size 3.5 µm) before amperometric detection with a carbon-paste working electrode at 780 mV vs. the SCE. The detection limit is 0.5 ppm, compared with 12 ppm by a gas diffusion system based on the same reaction, and at 4.5 ppm (v/v) the coefficient of variation is 2.9% (n = 10). The sampling rate is 25 h-1.
Nitrogen dioxide Environmental Amperometry Electrode

"Determination Of Total Carbon Dioxide In Beer And Soft Drinks By Gas Diffusion And Flow Injection Analysis"
J. Autom. Methods Manag. Chem. 1995 Volume 17, Issue 3 Pages 105-108
ESBJ&Ouml;RN LJUNGGREN and BO KARLBERG

Abstract: Beer or carbonated soft drinks were made alkali by the addition of 10 M NaOH and a sample was injected into a carrier stream (1.2 ml/min) of water. The carrier stream merged with a reagent stream (1.2 ml/min) of 0.2 M H2SO4, passed through a mixing coil (30 cm x 0.7 mm i.d.) and went into a gas diffusion cell with bromocresol purple indicator solution as the acceptor solution. The absorbance was then read at 430 nm. Beer's law was obeyed up to 9 g/l of CO2. The CO2 contents of Tuborg and Pripps beer, coke and club soda are tabulated.
Carbon dioxide Beer Soft drink Spectrophotometry

"Automation Of Flow Injection Gas Diffusion Ion Chromatography For The Nanomolar Determination Of Methylamines And Ammonia In Seawater And Atmospheric Samples"
J. Autom. Methods Manag. Chem. 1995 Volume 17, Issue 6 Pages 205-212
STUART W. GIBB, JOHN W. WOOD, R. FAUZI, and C. MANTOURA

Abstract: The automation and improved design and performance of Flow Injection Gas Diffusion-lon Chromatography (FIGD-IC), a novel technique for the simultaneous analysis of trace ammonia (NH3) and methylamines (MAs) in aqueous media, is presented. Automated Flow Injection Gas Diffusion (FIGD) promotes the selective transmembrane diffusion of MAs and NH3 from aqueous sample under strongly alkaline (pH > 12, NaOH), chelated (EDTA) conditions into a recycled acidic acceptor stream. The acceptor is then injected onto an ion chromatograph where NH3 and the MAs are fully resolved as their cations and detected conductimetrically. A versatile PC interfaced control unit and data capture unit (DCU) are employed in series to direct the selonoid valve switching sequence, IC operation and collection of data. Automation, together with other modifications improved both linearity (r2 > 0.99 MAs 0-100 nM, NH3 0-1000 nM) and precision (< 8%) of FIGD-IC at nanomolar concentrations, compared with the manual procedure. The system was successfully applied to the determination of MAs and NH3 in seawater and in trapped particulate and gaseous atmospheric samples during an oceanographic research cruise. (33 References)
Ammonia Amines, methyl Sea HPIC

"Development Of A Gas Diffusion FIA System For Online Monitoring Of Ethanol"
J. Biotechnol. 1990 Volume 14, Issue 1 Pages 127-140
Wolfgang K&uuml;nnecke and Rolf D. Schmid*

Abstract: A flow injection analysis (FIA) system for online monitoring of ethanol in cultivation media was developed, which combines the selectivity of a gas diffusion membrane with the substrate specificity of immobilized alcohol oxidase (AOD). The optimization of membrane material and immobilized enzyme was performed using different FIA modes such as dual detection and dual injection. A simple modification of a polypropylene membrane with silicone enabled a very flexible adjustment of the linear range for alcohol detection between 0.0006 and 60% (v v-1). The ethanol content of cultivation media could be determined continuously with a frequency of 120-180 samples per hour with an excellent correlation to gas chromatographic analysis (r = 0.9996). The relative standard deviation for 10 successive injections was lower than 0.5%. Samples (10 µL) were injected into a carrier stream and passed into a perspex gas diffusion unit (52 mm x 1.4 mm x 0.5 mm) containing a composite polypropylene - silicone membrane and maintained at 30°C. The vapor diffused across the membrane into the acceptor stream (1.5 mL min-1) then into the enzyme reactor (2 cm x 2 mm) that contained alcohol oxidase immobilized (by the glutaraldehyde method) on pore glass. Electrochemical detection of the resulting H2O2 was with a platinum electrode at 700 mV vs. Ag - AgCl. The calibration graph was rectilinear from 0.0006 to 60% of ethanol and coefficient of variation (n = 10) was 0.5%. Sample throughput was 180 h-1.
Ethanol Fermentation broth Electrode Electrode Electrode

"Flow Injection Hydride Generation Atomic Absorption Spectrometry With A Gas Diffusion Unit Using A Microporous PTFE Membrane"
J. Flow Injection Anal. 1985 Volume 2, Issue 2 Pages 134-142
Manabu YAMAMOTO, Makoto YASUDA, Yuroku YAMAMOTO

Abstract: Performance of a newly made gas diffusion unit with porous PTFE tubing was examined as a gas-liquid separator of FIA manifold for hydride generation-atomic absorption spectrometry. Arsine generated from 0 to 10 ppb of arsenic was separated quantitatively from the sample solutions, when the length of porous PTFE tubing (ID: 3 mm, porosity: 70% ) is longer than 50 cm. Arsenic lower than 2 ppb, which corresponds to the concentration level of arsenic in seawater could be determined directly with a sample volume of 1 mL. Sample throughput was 150/h.
Arsenic Sea Spectrophotometry

"Flow Injection Analysis Of Ultratrace Sulfide In Water By Membrane Separation-chemiluminescence Detection"
J. Flow Injection Anal. 1987 Volume 4, Issue 1 Pages 15-19
Toyoaki Aoki, Toshi kazu Nosaka, Makoto Munemori

Abstract: A 2 mL sample is injected into a carrier stream of water (7.7 mL min-1) to which is then added 9 M H2SO4 (0.7 mL min-1). The stream then passes through the sleeve of a micro-porous membrane separator through the centre of which a stream (0.4 mL min-1) of luminol solution flows to a chemiluminescence cell with a photomultiplier tube. The calibration graph is rectilinear for 0.2 to 10 µM-S2- and the limit of detection is 80 nM; the coefficient of variation (n = 4) for 5 µM was 0.7%. In the determination of 0.16 ppm of S2-, 50 ppm of CO32- or NO2- depressed the signal by 9 or 7%, respectively. There was no interference from Co(II), Cr(III) or Cu(II).
Sulfide Environmental Chemiluminescence

"Flow Injection Analysis Of Ammonia In Water With Membrane Separation UV Detection"
J. Flow Injection Anal. 1988 Volume 5, Issue 2 Pages 95-100
Toyoaki Aoki

Abstract: A double-tube membrane separation system, comprising a micro-porous PTFE inner tube and a PTFE outer tube, is applied in the flow injection determination of NH3 in water. Molecular NH3, produced by mixing a sample with 1 M NaOH in the outer tube, permeates the micro-porous PTFE to react with 1 mM NaClO in the inner tube. The solution in the inner tube then flows to an UV detector for measurement of the absorbance at 290 nm. The decrease in absorbance is proportional to NH3 concentration. for 6 µM. The detection limit is 1 µM and the coefficient of variation (n = 5) at 25 µM was 7.8%. The response time is 1.7 min with 30 cm of micro-porous PTFE. A double-tube membrane separation system, comprising a micro-porous PTFE inner tube and a PTFE outer tube, is applied in the flow injection determination of NH3 in water. Molecular NH3, produced by mixing a sample with 1 M NaOH in the outer tube, permeates the micro-porous PTFE to react with 1 mM NaClO in the inner tube. The solution in the inner tube then flows to an UV detector for measurement of the absorbance at 290 nm. The decrease in absorbance is proportional to NH3 concentration. for 6 µM. The detection limit is 1 µM and the coefficient of variation (n = 5) at 25 µM was 7.8%. The response time is 1.7 min with 30 cm of micro-porous PTFE.
Ammonia Environmental Spectrophotometry

"Simultaneous Determination Of Cyanide And Sulfide By Reversed Flow Injection Analysis"
J. Flow Injection Anal. 1994 Volume 11, Issue 1 Pages 58-67
Huiliang, M.;Jingfu, L.;Jianzhang, F.;Yue, G.

Abstract: A diagram of the optimized manifold is given. Sample was mixed with a stream of EDTA/HCl solution (0.4 ml/min) to form the donor stream which was heated to 60°C whilst passing through a PTFE coil (1 m x 0.7 mm i.d.) in the thermostat. Liberated HCN diffused through the PTFE membrane and was adsorbed by 5 mM NaOH acceptor solution the acceptor solution was then mixed with chloroamine-T/phosphate buffer solution Pyridine-barbiturate reagent was injected and the absorbance was measured at 494 nm for the separated cyanide (I). Alternatively, the donor stream was adjusted to pH 4.7 by mixing with a sodium acetate solution and then with an Fe(III) (1,10-phenanthroline chromogenic reagent. The absorbance was measured at 505 nm for sulfide (II). The detection limits of I and II were 0.2 and 0.4 mg/;, respectively. The corresponding RSD (n = 11) were 0.5 and 0.7% at 3 and 10 mg/l, respectively. Carbonate, nitrate, formaldehyde, iodide, thiocyanate and bromide did not interfere.
Cyanide Sulfides Environmental Spectrophotometry

"Total Volatile Acids: Temperature Dependent Decomposition Indicator In Halibut Determined By Flow Injection Analysis"
J. Food Prot. 1994 Volume 57, Issue 6 Pages 505-508
Hollingworth, Thomas A.; Hungerford, James M.; Barnett, James D.; Wekell, Marleen M.

Abstract: Total volatile acids (TVA) is a well known indicator for the decomposition of seafood products. A flow injection analysis (FIA) method, using a gas diffusion cell at elevated temperature, was developed for the determination of TVA in fish and applied to halibut. The FIA method is simple and rapid. The results of this study indicate that the correlation between levels of TVA and degree of decomposition is temperature dependent.
Acid, volatile, total Halibut

"Determination Of Total Sulfur Dioxide In Beer By Flow Injection Spectrophotometry Using Gas-diffusion And The Merging Zones Technique"
J. Inst. Brew. 1998 Volume 104, Issue 4 Pages 203-205
S&iacute;lvia M. V. Firnandes, Antonio O. S. S. Rangel, Jos&eacute; L. F. C. Lima

Abstract: A flow injection system for the determination of total sulfur dioxide in beer is described. The methodology involves the same colorimetric reaction of the reference method between SO2, p-rosaniline and formaldehyde. The sample is introduced into the manifold without previous pretreatment, the hydrolysis process, isolation of the SO2 from the matrix and the colorimetric reaction, being carried out inside the flow tubes. To isolate the SO2, a gas-diffusion unit was included in the system and to minimize p-rosaniline consumption, a merging zones technique was used. The results obtained were in good agreement with a reference method (relative deviations lower than 5%), the precision being better than 2.5% (relative standard deviation). A sampling-rate of 30 samples per h was obtained and the consumption of p-rosaniline was reduced 10 fold when compared to the reference method.
Sulfur dioxide Beer Spectrophotometry

"Flow Injection Analysis Of Cyanide In Waste Water With Gas Diffusion Separation"
Kexue Tongbao 1986 Volume 31, Issue 24 Pages 1728-1728
ZHU ZHAOHAI, FANG ZHAOLUN

Abstract: An automated flow injection analysis system is described for the determination of CN-, which is separated from acidified waste water samples at 60°C by online gas diffusion through a PTFE membrane into 0.025 M NaOH as acceptor solution. The sample loop was used for pre-concentration of CN- before analysis by the isonicotinic acid - pyrazolone colorimetric method. The detection limit of CN- was 6 µg L-1 and the coefficient of variation was 1.4% (n = 22) for 0.5 mg L-1 of CN-. Recoveries were 92 to 105%.
Cyanide Waste Spectrophotometry

"Routine Analysis Of Acetone In Milk By Flow Injection Analysis"
Kiel. Milchwirtsch. Forschungsber. 1986 Volume 38, Issue 3 Pages 205-213
Diekmann, L.;Pabst, K.;Gravert, H.O.

Abstract: In milk samples from 109 cows of the experimental herd Schaedtbek, and 6677 cows in 162 dairy herds nearly 43,000 acetone [67-64-1] measurements were made by flow injection analysis (FIA). Untreated and preserved milk samples were pumped in exact dosages into a diffusion cell with a Teflon membrane, where the acetone diffuses into a reaction stream with hydroxylamine and methyl orange, and the reaction is recorded photometrically. With the equipment of Tecator Co. about 100 determinations/h could be made.
Acetone Milk Spectrophotometry

"Continuous-flow. Continuous Determination Of Ammonium In Water And Waste Water"
LaborPraxis 1988 Volume 12, Issue 5 Pages 542-547
Braumann, T.

Abstract: The method is based on the diffusion of NH3 through a selective gas-permeable membrane and collection for differential conductometric detection of NH4+ in H3BO3 solution Use of the GAT N-360 continuous-flow apparatus (illustrated diagrammatically) permits determination of NH3 over a range of 20 to 1000 ppb and analysis of 60 samples h-1 with no significant interference. The method is easily automated. Introduction of a reduction cartridge permits determination of NO3- and NO2- as well as NH3.
Ammonium Nitrate Nitrite Environmental Waste Electrode

"Flow Injection Analysis For The Determination Of Ammonium In Water"
LaborPraxis 1997 Volume 21, Issue 4 Pages 72-75
Desor, M.

Abstract: A description is given of the DIN 38406 method for determining ammonium nitrogen in water by FIA. Samples were filtered (0.45 µm) and adjusted to a pH of 3. Portions were injected into a carrier stream of water which then mixed with alkaline EDTA solution. The liberated NH3 diffused through a semi-permeable membrane into an acceptor solution of bromocresol violet, bromothymol blue and cresol red, adjusted to a pH of 5.3, and the absorbance was measured at 590 nm. Calibration graphs were linear from 10^-1000 µg/l N, with a detection limit of 5 µg/l. At 500 µg/l, the RSD was 1.02% (n = 12). The throughput was 60 samples/h. A complete analytical system for this is the Lachat QuikChem Model 8000 (Zellweger Analytics GmbH, Munich, Germany), including a software package for control and evaluation, for use with a PC and Windows. The system can be combined with ion chromatography measurements.
Ammonium, nitrogen Water Sample preparation Spectrophotometry

"Rapid, Highly Sensitive Technique For The Determination Of Ammonia In Seawater"
Mar. Biol. 1986 Volume 91, Issue 2 Pages 285-290
S. W. Willason and K. S. Johnson

Abstract: The water sample is injected into a carrier stream and merges with aqueous NaOH (containing citrate to prevent interference from Ca and Mg), which converts the NH4+ in the sample into NH3. The NH3 diffuses through a hydrophobic PTFE membrane (76 µm thick) into an acceptor stream of aqueous NaCl containing phenol red as indicator. The absorbance of the resulting solution is monitored at 565 nm, and the results are processed by computer. The detection limit is 0.05 µM, and the upper limit is 100 µM. Up to 60 determinations can be carried out in 1 h. Details of the flow system and the diffusion cell are given.
Ammonia Sea Spectrophotometry

"A Technique For The Measurement Of Total Ammonia In Small Volumes Of Seawater And Haemolymph"
Ophelia 1993 Volume 37, Issue 1 Pages 31-40
Hunter, D.A.;Uglow, R.F.

Abstract: A rapid and precise technique combining flow injection analysis and gas diffusion is described for the measurement of total ammonia (NH-3 + NH-4+) in small volumes (100-450 µl) of seawater and diluted haemolymph. Calibration of the method with seawater ammonia standard solution in range 5.0-50.0 µmol ammonia L-1 (n = 6) gave linear calibration curves (r = 0.999 in each case) with precision in the range 0.2-3.0%. Precision of measurement of ammonia in samples of seawater and diluted haemolymph was 0.9-3.3% (n = 11-13). The lower limit of detection is 0.20 µmol ammonia l-1. Thirty determinations can be made per hour.
Ammonia, total Sea Haemolymph Fluid

"New Flow Injection Analyser For Monitoring Trace Hydrogen Cyanide In Process Gas Streams"
Process Control Qual. 1994 Volume 5, Issue 4 Pages 259-265
D.C. Olson, S.R. Bysouth, P.K. Dasgupta and V. Kuban

Abstract: The analyzer. is shown diagramatically. The FIA manifold is a three-stream configuration. The main stream comprising a caustic solution flowed through a gas-permeation unit (GPU) which acted as the sample loop. The HCN permeated the walls of the silicane tubing and was collected into the caustic solution The HCN concentrations became enriched before being flushed from the GPU and merging with a buffered chloramine-T stream and then with a buffered reagent mixture of isonicotinic acid and 3-methyl-1-phenyl-2-pyrazalin-5-one. The intensely colored purple product formed was measured at 630 nm in an optical cell. A pH cell downstream from the detector was used for pH monitoring as the system is pH sensitive with an optimum response in the pH range from 6.5-7.3. The flow rates are given. The system was capable of measuring from low ppb to high ppm levels of HCN in gas streams in the presence of at least 5000 ppm of H2S. The method may be used for other gases such as H2S, CO2, SO2 and NH3.
Hydrogen cyanide Gas Spectrophotometry

"Automated Measurement Of Aqueous Ozone Concentration"
Process Control Qual. 1995 Volume 6, Issue 4 Pages 229-243
J.L. Darby, D.P.Y. Chang, P.S. Coggin, H.K. Chung and P.K. Dasgupta

Abstract: Three previously described systems (Dasgupta et al. Am. Water Works Assoc. Research Foundation Report, 1993) namely a FIA system, a gas permeation membrane-based device and a nebulizer-based system, for the automated measurement of aqueous ozone were evaluated in field tests. Total dissolved solids, oxidizable organic matter and suspended solids seriously affected the performance of the membrane and nebulizer-based systems. The dual detector FIA system was simple, fast and efficient with detection limits of 10^-20 µg/l. The effects of interferences are discussed.
Ozone Environmental

"Flow Injection Determination Of Ammonium And Nitrate In Soil By The Diffusion Conductivity Method"
Rev. Bras. Cienc. Solo 1992 Volume 16, Issue 3 Pages 325-329
Coelho, N.M.M.;Cantarella, H.;De Andrade, J.C.

Abstract: An alternative procedure is proposed for the determination of ammonium and nitrate in soils using a flow injection analysis (F.I.A.) system, operated in a single line configuration with conductivity detection. This procedure allows the determination of NH4+ and NO3-, separately, with reactions producing ammonia, which is separated from the reaction medium by gaseous diffusion and transferred to a receiving stream of boric acid. The ammonia is converted to NH4+ ions and quantified by conductivity measurements. Under the experimental conditions, the calibration graphs for both NH4+ and NO3- are linear, up to 7.5 and 5.0 µg/ml, respectively. The method allows a sampling rate of 90 determinations per hour with a precision of `1% for NH4+ and NO3-. This method, which is free from interference, was applied to soil samples, using a 1.0 M KCl extracting solution. The results compared favourably with those obtained by the steam distillation procedure, with the F.I.A. system showing better precision.
Nitrate Ammonium Environmental Conductometry

"Flow Injection Analysis. 1. Principles And Working Methods"
Rev. Chim. 1990 Volume 41, Issue 5-6 Pages 490-495
Danet, A.F.;Luca, C.

Abstract: A review is presented, with 44 references, covering a brief history of the cited method, its principles and mathematical analysis. The various techniques and apparatus used are described, with examples of their use, including continuous- or interrupted-flow, titrations, solvent extraction and gas diffusion methods.
Sample preparation

"Determination Of Total Nitrogen In Soil Digests By Gas Diffusion Flow Injection Analysis"
Turang Tongbao 1986 Volume 1986, Issue 1 Pages 37-38
Sun Lijing, Li Lin, Fang Zhaolun

Abstract: For quantitation of total nitrogen in soil, the sample was treated with a catalytic mixture containing K2SO4, CuSO4, Se, and H2SO4 to convert the nitrogen into NH4+. The solution was then subjected to flow injection analysis in an alkaline solution. The NH4+ was converted into NH3(g) by the alkali and diffused through a PTFE membrane into an indicator solution containing cresol red (0.02), bromothymol blue (0.04), and bromocresol purple (0.08 g/100 mL). Upon reaction with NH3, the indicator solution underwent a color change that was detectable at 590 nm.
Nitrogen, total Environmental Sample preparation

"Study On The Systematic Analysis Of Squeezed Water From Soil By Flow Injection Analysis"
Yankuang Ceshi 1991 Volume 10, Issue 3 Pages 166-170
Lin, S.L.;Shuai, Q.;Qiu, H.O.

Abstract: Sample (2 to 5 ml) was systematically analyzed in the sequence of (i) conductivity, (ii) pH value, (iii) HCO3- by flow injection analysis (FIA) - gas diffusion method, (iv) K+, Na+, Ca2+ and Mg2+ by FIA - AAS, (v) Cl- by FIA - photometry and (vi) SO42- by FIA - turbidimetry. All required procedures were described (details illustrated) for the complete scheme and for the three FIA systems. These methods were time saving and highly reproducible. Results agreed well with calculated values of synthetic samples.
Water Water Conductometry Spectrophotometry Turbidimetry

"Determination Of Milk Urea By Flow Injection Analysis"
Zentralbl. Veterinarmed. A 1986 Volume 33, Issue 1 Pages 53-58
G. Andersson, L. Andersson, G. Carlstr&ouml;m

Abstract: A method for flow injection analysis of urea in milk is described. The sample is introduced into a current of urease solution in which urea is enzymatically split into carbon dioxide and ammonia. After adding sodium hydroxide, the free ammonia diffuses through a teflon membrane into a stream of phenol red solution. The change of color in the indicator solution caused by the ammonia-induced pH alteration is measured in a flow photometer. The accuracy of the method is shown to be good, and the capacity is about 100 samples per hour.
Urea Milk Spectrophotometry

"Determination Of Bromide By A Chemiluminescence Method Combined With Dynamic Gas Extraction In Flow Injection Analysis"
J. Anal. Chem. 1989 Volume 44, Issue 9 Pages 1585-1588
Pilipenko, A.T.;Terletskaya, A.V.;Zui, O.V.

Abstract: Sample (0.1 to 1.5 ml) containing Br- (2 to 500 ng) was oxidized with 9.2 M H2SO4 - 0.15 M K2Cr2O7 (7 ml). The Br was extracted into a stream of gas (1.3 to 1.7 l min-1) and detected chemiluminometrically in 4 mL of 0.02 M NaOH containing 0.4 mM luminol. The detection limit was 1.3 µg L-1 and the analysis time was 1 min.
Bromide Chemiluminescence Sample preparation

"Flow Injection Analysis. Spectrophotometric Determination Of Ammonium And Hydrogen Carbonates In Atmospheric Precipitations"
J. Anal. Chem. 1993 Volume 48, Issue 1 Pages 35-42
Eremina, I.D.;Shpigun, L.K.;Zolotov, Y.A.

Abstract: Sample (200 µL) was added intermittently to a flow of water (2 ml/min) by a peristaltic pump and mixed with 0.1 M NaOH (for the determination of NH4+) or 0.2 M H2SO4 (for the determination of bicarbonate) in a mixing spiral before entering the gas diffusion cell. The NH3 or CO2 gas was separated by a porous PTFE membrane and was merged with the color reagent stream comprising phenol red or bromocresol purple (50 mg/l) for the determination of ammonium or bicarbonate ions, respectively. The absorbance change was measured at 565 nm (phenol red) or 590 nm (bromocresol purple). Calibration graphs were linear from 0.1-5 mg/l and 0.5-20 mg/l of ammonium and bicarbonate ions, respectively. The corresponding RSD were 1-2% and 2-3%.
Ammonium Bicarbonate Rain Spectrophotometry

"In-line Membrane Separation Method For Sulfide Monitoring In Wastewaters Exploiting Multisyringe Flow Injection Analysis"
Anal. Chim. Acta 2004 Volume 524, Issue 1-2 Pages 89-96
Graciela de Armas, Laura Ferrer, Manuel Mir&oacute;, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: A fully automated multisyringe flow injection analysis (MSFIA) system coupled to gas-diffusion (GD) separation is proposed for the spectrophotometric determination of sulfide in urban wastewaters containing suspended solids. No preliminary batch sample treatment is required. The method carried out in a multicommutated system is based on analyte release as hydrogen sulfide from the donor channel of the GD module into a stagnant recipient solution composed of N,N-dimethyl-p-phenylene diamine (DMPD) and Fe(III). The methylene blue dye generated in-line via oxidative coupling is subsequently delivered downstream to a miniaturized flow-through light-emitting diode (LED)-based optical fiber plug-in spectrophotometer. The effect of various experimental variables on gas transfer across the membrane and concentration enhancement in the receiver solution via iterative flow reversals are discussed. Under the optimized chemical and hydrodynamic variables, the GD-MSFIA method features coefficients of variation better than 0.8% (n=10) at the 10 mg L-1 level, a linear working range of 0.5-20 mg L-1 sulfide, a 3s blank-detection limit of 0.03 mg L-1 and an injection throughput of 13 h-1 for a sample volume of 700 µl and a forward flow mode. The analytical performance of the proposed GD-MSFIA system is also critically compared with that of in-line dialysis separation schemes using passive semi-permeable hydrophilic membranes. Accuracy was assessed by using the batch APHA-AWWA-WPFC standard method as an external reference.
Sulfide Waste Spectrophotometry

"A Multisyringe Flow Injection System Coupled With A Gas Diffusion Cell For Ammonium Determination"
Int. J. Environ. Anal. Chem. 2003 Volume 83, Issue 3 Pages 233-246
Jana Klimundov&aacute;, Rafael Forteza, V&iacute;ctor Cerd&aacute;

Abstract: A multisyringe flow injection system for ammonium determination based on the coupling of a gas-diffusion separation cell has been developed. By using a multisyringe burette equipped with additional three-way solenoid valves, the system allows the use of different reagents or samples with further propelling into a gas-diffusion unit. Two possibilities were tested to increase the sensitivity and repetitivity: flow delay during the diffusion of the ammonia formed and use of successive flow reversals.
Ammonium

"Interfacing In-line Gas-diffusion Separation With Optrode Sorptive Preconcentration Exploiting Multisyringe Flow Injection Analysis"
Talanta 2005 Volume 68, Issue 2 Pages 343-350
Laura Ferrer, Graciela de Armas, Manuel Mir&oacute;, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: An automatic multisyringe flow injection analysis (MSFIA) system coupling a flow-through optical fiber diffuse reflectance sensor with in-line gas-diffusion (GD) separation is proposed for the isolation, pre-concentration and determination of traces of volatile and gas-evolving compounds in samples containing suspended solids, with no need for any preliminary batch sample treatment. The flowing methodology overcomes the lost of sensitivity of the in-line separation technique, when performed in a uni-directional continuous-flow mode, through the implementation of disk-based solid-phase extraction schemes. The high selectivity and sensitivity, the low reagent consumption and the miniaturization of the whole assembly are the outstanding features of the automated set-up. The proposed combination of techniques for separation, flow analysis, pre-concentration and detection was applied satisfactorily to sulfide determination in environmental complex matrixes. The method based on multicommutation flow analysis involves the stripping of the analyte as hydrogen sulfide from the donor channel of the GD-module into an alkaline receiver segment, whereupon the enriched plug merges with well-defined zones of the chormogenic reagents (viz., N,N-dimethyl-p-phenylenediamine (DMPD) and Fe(III)). The in-line generated methylene blue dye is subsequently delivered downstream to the dedicated optrode cell furnished with a C18 disk, while recording continuously the diffuse reflectance spectrum of the pre-concentrated compound. This procedure provides a linear working range of 20-500 µg l-;1 sulfide with a relative standard deviation of 2.2% (n = 10) at the 200 µg L-;1 level, and a detection limit of 1.3 µg L-;1.
Sulfide Sea Ground Waste Optrode

"Photodissociation/gas-diffusion Separation And Fluorimetric Detection For The Analysis Of Total And Labile Cyanide In A Flow System"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 6 Pages 516-520
E. Miralles, R. Compa&ntilde;&oacute;, M. Granados, M. D. Prat

Abstract: Total cyanide species are determined in a flow injection system which includes UV-photodissociation, gas-diffusion separation and spectrofluorimetric detection. Without the irradiation step, only cyanide easily released in acid medium, i.e. labile cyanide, is determined. Cyanide diffuses through a microporous PTFE membrane from an acid donor stream to a sodium hydroxide acceptor stream. Then, the transferred cyanide reacts with o-phthalaldehyde and glycine to form a highly fluorescent isoindole derivative. Complete cyanide recoveries were obtained for the most important metal cyanide complexes found in environmental samples, excepting cobaltocyanide. The sampling frequency for total cyanide was 4 samples h-1 and the detection limit was 0.4 µg L-1. Recoveries of total cyanide from river water obtained with this method are about 90% of those obtained with APHA Method 4500-CN C for total cyanide.
Cyanide, total River Fluorescence