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
Website: @unf

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Classification: Environmental -> air

Citations 84

"Preconcentration With Membrane Cell And Adsorptive Polarographic Determination Of Cyanides In Air"
Anal. Chim. Acta 1999 Volume 382, Issue 3 Pages 283-289
Zheng-Qi Zhang, Sheng-Zong Chen, Yan-Fei Li and Ming-Fan Zhu

Abstract: The present paper describes a procedure that cyanides in air were pre-concentrated in a membrane cell and their content was determined by adsorptive polarography. In a pH 8.4 buffer solution the cyanide ion can form a quaternary complex with Co(II), α,α-dipyridyl and ethanolamine. The complex can be adsorbed at the mercury electrode and yields a sensitive oscillopolarographic wave at -1.45 V. Over the range 1.0 x 10^-8 - 1.0 x 10^-7 M, the peak currents are linearly proportional to the concentration of the cyanide. The detection limit is 6.0 x 10^-9 M. First the cyanides in the air samples were pre-concentrated in the membrane cells using 0.10 M NaOH solution, then their content was determined by complex adsorptive polarography.
Cyanide Polarography Chromatomembrane Preconcentration

"A New Device For Improving Sensitivity And Stabilization In Flow Injection Analysis"
Anal. Chim. Acta 1978 Volume 97, Issue 2 Pages 427-431
H. Bergamin F, B. F. Reis and E. A. G. Zagatto

Abstract: In flow injection anal., an aqueous sample is injected into a continuous moving carrier stream of reagent. If the sample injection is done by forcing the liquid into the carrier stream, the regularity of the flow is disturbed momentarily. There is a temporary difference in mixing ratios at those points in the manifold where 2 streams meet. This can cause a change in the blank values. To minimize these changes, while increasing sensitivity, a confluence manifold was used for the spectrophotometric and/or turbidimetric determination of NO2-, SO42-, and Cl- in natural waters. An injection pulse dampener is described and is recommended when flow injection confluence systems are employed for anal. of very dilute samples.
Chloride Chlorine Chlorate ion Perchlorate Nitrite Sulfate Spectrophotometry Turbidimetry Apparatus Pulse dampener

"A Detailed Study Of Sample Injection Into Flowing Streams With Potentiometric Detection"
Anal. Chim. Acta 1978 Volume 98, Issue 2 Pages 193-203
Zs. Fehér and G. NagyK. Tóth and E. Pungor

Abstract: A new method developed by combining manual or coulometric injection into flowing streams and potentiometric detection is described. The potential-time curves obtained in a flow-through detector as a result of single injections are handled theoretically and examined practically. The effects of experimental parameters, concentrations and flow rates on the signal are discussed. A systematic survey of the potential use of the technique in analysis is given. Species can be determined easily either in the flowing stream or in the injected sample. Some applications in pharmaceutical and other types of analysis are listed, and the main advantages of the technique are summarized.
Bromine Chlorine Cyanide Thiocyanide Indium Enzyme, cholinesterase Uric acid Enzyme, urease Glucose Enzyme, glucose oxidase Urea Nitrogen, urea Potentiometry Coulometric injection

"Determination Of Sulfur Dioxide In Solutions By Pyridinium Bromide, Perbromide, And Titrimetric And Flow Injection Procedures"
Anal. Chim. Acta 1981 Volume 123, Issue 1 Pages 351-354
T. R. Williams, S. W. McElvany and E. C. Ighodalo

Abstract: Sulfur dioxide can be determined by its reaction with pyridinium bromide perbromide using photometric titrations and flow injection procedures. Both methods are useful down to 30 ppm, and are unaffected by ammonia or nitrogen dioxide. Both mercury(II) and EDTA interfere under some circumstances.
Sulfur dioxide Spectrophotometry Sample splitting Titrations

"Flow Injection Method For The Sulfide Determination By The Methylene Blue Method"
Anal. Chim. Acta 1981 Volume 128, Issue 1 Pages 163-168
D. J. Leggett, N. H. Chen and D. S. Mahadevappa

Abstract: Flow injection determination of sodium sulfide and hydrogen sulfide in solution through the methylene blue spectrophotometric procedure is described. The carrier streams are N,N-dimethylaniline sulfate (5.4 mM, HCl solution) and iron(m) ammonium sulfate (14.2 mM, HCl solution) and are merged before injection of sulfide (in 0.01 M NaOH). The sampling rate is 210 per hour. The effect of reagent concentrations and interferents on the determination has been investigated.
Sulfide Hydrogen sulfide Spectrophotometry

"Determination Of Sulfite In A Flow Injection System With Chemiluminescence Detection"
Anal. Chim. Acta 1983 Volume 147, Issue 1 Pages 401-404
Masaaki Yamada, Tsuneo Nakada and Shigetaka Suzuki

Abstract: The emission produced by sulfite on oxidation by permanganate in acidic solution in the presence of riboflavin phosphate or brilliant sulfaflavine is used to determine 0.9-35 ng of sulfite. Only sulfide and thiosulfate also give emissions.
Sulfite Chemiluminescence

"Determination Of Ammonia In Air And Aqueous Samples With A Gas-sensitive Semiconductor Capacitor"
Anal. Chim. Acta 1984 Volume 164, Issue 1 Pages 127-138
F. Winquist, A. Spetz and I. Lundström, B. Danielsson

Abstract: The properties of a new type of ammonia gas-sensitive semiconductor capacitor are described. The sensor is based on a palladium MOS field-effect capacitor with a thin layer (3 nm) of iridium surrounding the palladium gate. The lower limit of detection for ammonia in air is 1 ppm (0.59 mg kg-1). The analytical characteristics and temperature-dependence of the sensor in measurements of ammonia in air are evaluated. Ammonia in aqueous solutions is determined by the use of a continuous flow system utilizing a gaspermeable membrane in combination with the sensor. The calibration plot of the voltage drop of the capacitor vs. ammonia concentration in 150 µL samples is linear in the concentration range 0.2 x 10^-6-5 x 10^-5 M. Ammonia is determined in rain and river water as well as in whole blood and blood serum; 15 samples per hour can be assayed. Analytical recovery studies and the selectivity properties of the system are described and discussed. Finally, the properties of the flow-through system in continuous monitoring are described.
Ammonia Electrode

"Determination Of Hydrogen Cyanide In Air Using Mass Amplification By Heavy-ligand Replacement On A Coated Quartz Piezoelectric Crystal"
Anal. Chim. Acta 1986 Volume 182, Issue 1 Pages 123-131
J. F. Alder, A. E. Bentley and P. K. P. Drew

Abstract: Piezoelectric crystals coated with bis(pentane-2,4-dionato)nickel were used as sensors for 13 to 93 ppm of HCN in air. The displacement of the pentan-2,4-dione ligand (L) by the lighter HCN gave an increase in sensitivity, compared with simple absorption of the analyte. A continuous-flow system was used at r.h. of 40 to 92%. The lifetime of the device was limited by hydrolysis. Reproducibility was poor due to inconsistencies in the crystal coating technique. Other transition metal complexes were evaluated as potential coatings. Reaction rates with HCN decreased in the order NiL2, CoL2, CuL2, CoL3, PdL2.
Hydrogen cyanide Piezoelectric crystal Gas stream

"Determination Of Mercury In Air By Means Of Computerized Flow Constant-current Stripping Analysis With A Gold Fiber Electrode"
Anal. Chim. Acta 1987 Volume 201, Issue 1 Pages 269-273
Huang Huiliang, Daniel Jagner and Lars Renman

Abstract: Mercury in air was determined after collection in potassium permanganate or sodium carbonate solution. The mercury concentration in these solutions was determined in a computerized flow potentiometric stripping analyzer with a 10 µm gold fiber working electrode, a glassy carbon reference electrode and a platinum counter electrode. After sample electrolysis for 1-10 min, stripping was done in a 1 mg L-1 gold(III) solution in 0.01 M nitric acid/0.01 M sodium nitrate with a constant stripping current of 0.50 µA. Results obtained for flue gas samples were in good agreement with results from cold-vapor atomic absorption spectrometry.
Mercury Amperometry Electrode Computer

"Hollow-fibre Membrane For Sample Introduction In A Flow Injection System. Determination Of Carbon Disulfide In Air"
Anal. Chim. Acta 1989 Volume 226, Issue 1 Pages 171-175
I. C. Van Nugteren-Osinga, M. Bos and W. E. Van Der Linden

Abstract: The computer-controlled sampling system consisted of an asymmetric hollow-fiber membrane module made from three fibers (20 cm x 0.65 mm o.d. x 0.30 mm i.d.) through which ethanol could be pumped. The module was exposed to an atmosphere containing varying amounts of CS2, which accumulated in the ethanol when pumping was stopped for a fixed period of time. When pumping was resumed the ethanol stream was mixed with a reagent stream (consisting of ethanolic diethylamine, triethanolamine and Cu acetate), and the Cu(II) complex formed was detected at 421.5 nm. Signal data were collected at a sampling rate of 2 s-1, and the calibration graph (for 15 s pump off and 45 s pump on) was rectilinear from 3 to 30 mg l-1, with a standard deviation (n = 20) of 0.2 to 0.5 mg l-1.
Carbon disulfide Complexation Hollow fiber membrane Computer

"Continuous Monitoring Of Gas-phase Species At Trace Levels With Electrochemical Detectors. II. Detection Of Chlorine And Hydrogen Chloride"
Anal. Chim. Acta 1991 Volume 248, Issue 2 Pages 391-398
Wojciech Matuszewski and Mark E. Meyerhoff

Abstract: The sample gases were trapped through the wall of a microporous polypropylene tube into the recipient buffer solution [10 mM borate (pH 9.0)]. Detection was initially made potentiometrically with Ag - AgCl working electrode, followed by biamperometric detection at 100 mV with two Pt electrodes. The limits of detection were 0.75 and 2.1 ppb of Cl and HCl gas, respectively, with use of the continuous-flow method. The method was applicable to air. For Part I, see previous abstract.
Chlorine Hydrogen chloride Biamperometry Electrode Electrode Potentiometry Buffer Microporous membrane PPB

"Determination Of Nanomole Amounts Of Sulfur Dioxide In Air By Flow Injection Conductimetry With Online Preconcentration"
Anal. Chim. Acta 1992 Volume 269, Issue 2 Pages 177-185
I. Gács*, and R. Ferraroli

Abstract: A sample of air was injected into the flow injection system (diagram given), passed through 0.2 M sulfamic acid to remove NO2 and HCl, then SO2 in the carrier gas stream was pre-concentrated as H2SO4 by absorption in a capillary denuder tube coated with 0.02 M H2O2; CO2, NO and H2S were removed with the carrier gas passing through the tube. The H2SO4-containing film was eluted with a circulating stream of the absorbent and was passed through a conical-plate electrolytic-conductivity µflow cell. The change in specific conductance due to H2SO4 was linearly related to the amount of SO2 in the sample (up to 55 nmol). The method could be used for detecting SO2 in aqueous SO32- solution Samples were injected into the sulfamic acid and the acidic solution was stripped with N. The detection limits were 1 µg L-1 for aqueous solution and 4 µg L-1 for gaseous samples. The time taken for the determination was 7 min. A simple and sensitive flow injection technique for measuring nanomole amounts of SO2 in gaseous atmospheres is presented. The samples are passed through 0.2 M sulfamic acid solution to eliminate constituents interfering with the final electrolytic conductivity measurement. SO2 is pre-concentrated from the carrier gas stream by absorption in a capillary denuder tube coated with 0.02 M H2O2 solution The H2SO4 formed in the liquid film is then eluted with a stream of the absorbent circulated through an electrolytic conductivity microdetector. The change in specific conductance due to the presence of the H2SO4 in the effluent stream is linearly related to the amt. of SO2 in the sample (55 nmol). The method can also be applied to the anal. of aqueous sulfite solutions In this case the samples are injected into the sulfamic acid, and the acidic solution is then stripped with a stream of nitrogen. The limit of detection for aqueous samples is 1 µg/L and for air samples 4 µg/m3. A simple determination, including sample preparation, takes 7 min. The precision is 5% (P = 95%) for 2.5-50 nmol of SO2. The selectivity of the system with respect to nitrogen oxides, NH3, HCl, and H2S was also examined
Sulfur dioxide Conductometry Preconcentration Interferences

"Permeation Denuder For Sampling And Continuous Analysis Of Gases. 1. System Configuration, Basic Studies And Application To Atmospheric Ammonia And Sulfur Dioxide"
Anal. Chim. Acta 1994 Volume 291, Issue 3 Pages 305-320
Wolfgang Frenzel*

Abstract: Recent developments of the coupling of permeation denuders with FIA are described. The principles of the method are outlined. The experimental variables that affect collection of gaseous compounds are considered and the behavior of tubular and planar denuders compared. Collection efficiency of the permeation denuders was assessed in terms of gas flow rate, type of membrane, and composition of absorber solution using NH3 and SO2 as test gases. The calibration methods are outlined.
Ammonia Sulfur dioxide Membrane Optimization

"Electro-osmotically Pumped Capillary Format Sequential Injection Analysis With A Membrane Sampling Interface For Gaseous Analytes"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 281-285
Shaorong Liu and Purnendu K. Dasgupta*

Abstract: An electro-osmotically pumped sequential injection analysis system with miniature diffusion scrubber (MDS) was described and utilized for the determination of NH3 at the ppb level. The MDS consisted of a polypropylene porous membrane tube (Celgard X-20, 0.02 µm mean pore size, 40% surface porosity) mounted inside a PTFE tube. The scrubber solution was propelled through the Celgard tube while the gas sample was pumped through the outer cavity. The scrubbing solution was 1 mM H2SO4 and was kept stationary during the sampling period. At the end of the sampling period, the scrubber solution was aspirated for 10 s (3.9 µL) and then reagents R1, R2 and R3 for 3 s (74 nl) , 5 s (120 nl) and 15 s (360 nl), respectively. The mixture was propelled through the detector where the absorbance at 630 nm was recorded. R1 was a mixture of 10 mg/ml of phenol and 5 mg/ml of sodium nitroprusside. R2 contained 20 mg/ml of EDTA and 20 mg/ml of NaOH. R3 was a sodium hypochlorite reagent prepared by diluting 8 mL of Clorox (5% NaOCl) to 100 mL. The pumping solution was 2 mM sodium tetraborate. The calibration graph for NH3 was linear for 0-250 ppb (by volume) with a gas pumping rate of 0.121 l/min and a sampling time of 4 min.
Ammonia Spectrophotometry Sequential injection Electroosmotic flow Celgard

"Spectrophotometric Flow-through Gas Sensor For The Determination Of Atmospheric Nitrogen Dioxide"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 109-114
D. Schepersa, G. Schulzea and W. Frenzelb,*

Abstract: A flow-through gas sensor has been developed which relies on membrane based analyte collection and trapping in a temporarily halted liquid absorber and in situ spectrophotometric detection of the reaction product formed in solution. Through a stop-and-go sequence of the absorber solution provision is made for real-time detection of the pre-concentration taking place in the minute absorber solution and ready elution after signal evaluation. The determination of nitrogen dioxide at concentration levels relevant to measurement of urban atmospheres is used to demonstrate the principle and capabilities of an inherently universal applicable gas sensing device. The detection chemistry used in the present work is identical to that of common standard methods (i.e., reaction of NO2 with mixed reagent containing sulfanilamide and N-(1-naphthyl)-ethylene-diamine) so that the same selectivity arises. The working range covered in this study is 50-250 µg/m3 NO2 with a time resolution of few seconds. Lower concentrations are accessible when longer pre-concentration times are used. Reasonable precision (typically < 5% RSD) and good long-term stability is given which makes frequent calibration unnecessary.
Nitrogen dioxide Spectrophotometry Sensor

"Determination Of Gaseous Carbon Dioxide By Enhancement Of Luminol-cobalt(II) Phthalocyanine Chemiluminescence: Analysis Of Atmospheric Air And Human Breath"
Anal. Chim. Acta 1996 Volume 329, Issue 3 Pages 305-310
Zhang-Hua Lan and Horacio A. Mottola*

Abstract: Atmospheric air at a minminium of 35 ml/min was pumped into a continuous-flow (1.2 ml/min) solution of 5 mM luminol/cobalt(II) phthalocyanine of pH 12.6 and the solutions mixed in a windowed black PTFE reaction cell. Log-log calibration graphs of the CO2 enhanced led light vs. CO2 were linear up to 800 ppm of CO2 with a detection limit of 1.5 ppm CO2. At 320 ppm CO2 a RSD (n = 11) of 1.2% was obtained with quantitative recoveries in the range 200-600 ppm of CO2. Using a modified apparatus, 100 µL human breath was injected into a continuous-flow (5.2 ml/min) of the 5 mM luminol/cobalt(II) phthalocyanine reagent and CO2 was detected as before. Using the modified apparatus, a response time to CO2 of 1 s and a recovery time of 2.6 s was observed. Sulfur dioxide, nitrogen oxides and ozone were adjusted to cause non-significant interference.
Carbon dioxide Chemiluminescence Interferences

"Determination Of Volatile Arsenicals In Ambient Air By Flow Injection"
Anal. Chim. Acta 1997 Volume 338, Issue 3 Pages 215-222
Joseph H. Aldstadt*, Don C. Olson and Alice F. Martin

Abstract: An FIA method was developed for the determination of trans-dichloro(2-chlorovinyl)arsine (lewisite, a chemical warfare agent) in air. The flow manifold was equipped with a gas permeation membrane sampling unit and a detector based on potentiometric-stripping analysis in the constant-current mode. Air samples were passed through the donor channel of the sampling unit at 200 ml/min for 5-15 min and the vapor-phase lewisite diffused through a Si or natural rubber non-porous membrane (0.66 or 0.27 mm wall thickness) into a stationary 0.01 M NaOH collector. Lewisite hydrolyzed in the alkaline medium and the generated arsenite ions were detected at a Au disc electrode at Ep = -475 mV vs. Ag/AgCl (3 M KCl). The effects of membrane type, membrane tube length, sampling time and sampling temperature were investigated using a dry N2 stream containing 0.99 ppb lewisite. The estimated working range of the method was 0.5-50 µg/m3 using a 15 min sampling period.
Arsine, trans-dichloro-(2-chlorovinyl)-8 Lewisite Potentiometric stripping analysis Electrode Gas stream Selectivity Silicone membrane Tubular membrane

"Membrane Introduction Mass-spectrometry"
Anal. Chim. Acta 1997 Volume 350, Issue 3 Pages 257-271
N. Srinivasan, R. C. Johnson, N. Kasthurikrishnan, P. Wong and R. G. Cooks*

Abstract: An overview of membrane introduction mass spectrometry (MIMS) is presented and comparisons are made with other direct sample introduction techniques. Special attention is given to the unique advantages and the limitations of newer variants on the MIMS technique, including affinity MIMS, reverse-phase and trap MIMS. The salient features of the interfaces used in MIMS are summarized and the various membrane materials commonly used are delineated. The applicability of MIMS is illustrated via discussion of (i) bioreactor monitoring (represented by yeast fermentation), (ii) environmental monitoring (illustrated by analysis of contaminated ground water samples) and (iii) online chemical reaction monitoring (exemplified by the photolysis of aryl esters). The applicability of MIMS to the analysis of environmental samples, including complex mixtures in water, air and soil, is noted. 77 References
Mass spectrometry Membrane Process monitoring Photochemistry Review

"Determination Of Glycerol In Water By Flow Injection Analysis - A Novel Way Of Measuring Viscosity"
Talanta 1976 Volume 23, Issue 5 Pages 409-410
D. BetteridgeJ. Rika

Abstract: Flow injection analysis of mixtures of glycerol and water suggested that precise results may be obtained for the composition of miscible liquid mixtures over a narrow range. Since the viscosity is an important factor in the extent of mixing it could be determined simply and rapidly by this technique.
Glycerol Spectrophotometry Viscosity

"Automated Determination Of Sulfite And Sulfur Dioxide By Cool-flame Molecular-emission Spectrometry After Reduction To Hydrogen Sulfide With Sodium Tetrahydroborate(III)"
Talanta 1992 Volume 39, Issue 11 Pages 1471-1478
Toyin A. Arowolo and Malcolm S. Cresser*

Abstract: Sample was mixed with NaBH4, acidified with 6 M HCl and carried by a continuous-flow stream into a gas - liquid separator where the evolved H2S is swept by N into a cool H - N flame. The intensity of the blue diatomic S2 emission generated was measured at 384 nm. A schematic diagram of the apparatus is presented. The experimental conditions were optimized for the effects of HCl concentration, NaBH4 volume and concentration, sample volume, flow rates and flame composition. Calibration graphs for sulfite were rectilinear at 24 µg mL-1 with a detection limit of 29 ng mL-1 and the coefficient of variation were 1.2 and 1.5% for 1 and 5 µg l-1, respectively. Samples could be analyzed at a rate of ~40 h-1. Some interferences (notably from sulfide) were found, but the effects could be minimized; there was no interference from NO2. The method was applied to the determination of SO2 in air and sulfite in wines.
Sulfite Sulfur dioxide Spectrophotometry Interferences Optimization

"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 Spectrophotometry Gas diffusion Sequential injection Valve

"Field Portable Flow Injection Analysers For Monitoring Of Air And Water Pollution"
Talanta 1996 Volume 43, Issue 6 Pages 915-925
Peter W. Alexandera,*, Lucy T. Di Benedettoa, Telis Dimitrakopoulosa, D. Brynn Hibbertb, J. Catherine Ngilab, Margaret Sequeirab and Damien Shielsb

Abstract: An overview of portable monitors for the analysis of aqueous and gas samples including chemical ion sensors, multi-sensor arrays, test kits, disposable test strips, submersible probes and gas analyzer.s is presented. The use of a portable flow injection potentiometric analyzer. and the monitoring of car exhaust gases, air pollution in houses and ethanol in alcoholic drinks are described. (29 references).
Potentiometry Portable Review Gas phase detection

"Determination Of Passive-sampled Sulfur Dioxide In Ambient Air As Sulfate Ion By Flow Injection Analysis With An Inline Reaction Column"
Talanta 1997 Volume 45, Issue 2 Pages 445-450
Yi Yanga, Xin-Xiang Zhanga, Takashi Korenagaa,* and Keiro Higuchib

Abstract: A modified FIA method was developed for the determination of sulphur dioxide (SO2) in ambient air collected by a passive sampler. SO2 was oxidized by hydrogen peroxide and determined as sulphate ion in solution. Barium-dimethylsulfoazo-III complex was used as spectrophotometric reagent. A BaSO4-immobilized in-line reaction column was introduced into the flow system to increase the sensitivity and reproducibility. An in-line cation exchange column was used to eliminate triethanolamine, which was used as the absorbent reagent in the passive sampler. Sulphate ions can be analyzed in the range of 0.08-10.00 mg L-1 with the RSD less than 1.6% at the rate of 15 samples h-1. It was satisfactory to apply this method to the analysis of sulphur dioxide in ambient air and the results agreed with those obtained by ion chromatography.
Sulfur dioxide Membrane

"Flow Injection Analysis Of Environmental Samples For Nitrate Using An Ion Selective Electrode"
Analyst 1977 Volume 102, Issue 1219 Pages 705-713
E. H. Hansen, Animesh K. Ghose and J. Ruzicka

Abstract: NO3- in soil extracts, wastewater, and fertilizer solutions was determined by addition of a pH 9.5 buffer of 10^-2 M Na tetraborate + 10^-2 M NaOH and measuring the peak max. value in a flow injection system with a NO3--selective electrode. Aqueous extracts of particulate NO3- in air were analyzed without pretreatment. The electrode consisted of tetraoctylammonium bromide in di-Bu phthalate and was calibrated at 10^-5 - 10^-2 M NO3-. For injection of 0.3 mL samples the anal. rate was 90 samples/h. The standard deviation was typically 0.2-0.5 mV, equivalent to 1-2%. The electrode lifetime was 2-3 months. A method is proposed for identifying and correcting for the presence of interferents by observing the shape of each peak and determining its negative elevation. Based on the flow injection principle and employing a nitrate electrode situated in a flow-through cell, a simple, reliable and sensitive method for the automated determination of nitrate and its use for analyzing soil extracts, waste waters, fertiliser solutions and air samples are described. At a sampling rate of 90 samples per hour a standard deviation of only 1-2% is typical. A new approach to identifying and correcting for the presence of interfering species in potentiometric measurements is discussed.
Nitrate Electrode Apparatus Interferences

"Potentiometric Determination Of Fluoride By A Combination Of Continuous-flow Analysis And The Gran Addition Method"
Analyst 1981 Volume 106, Issue 1269 Pages 1275-1280
J.-Cl. Landry, F. Cupelin and C. Michal

Abstract: method is described for the determination of fluoride ion by continuous-flow analysis combined with the Gran addition method using an ion-selective electrode.The Gran addition method is a reliable potentiometric technique and an advantage of its use is that, in addition to the determination of the free and total fluoride concentration in a complexed medium, the complexation rate is also measured. The drawback of the method is the difficulty in adjusting the peristaltic pumps, which is time consuming. However, this extra time is compensated for by the simultaneous determination of fluoride ion concentration and the complexation rate.For concentrations of fluoride ion between 0.5 and 100 mg 1-1, the precision is 5%.
Fluoride Potentiometry

"Continuous-flow Chemiluminescence Determination Of Sulfite And Sulfur Dioxide"
Analyst 1988 Volume 113, Issue 4 Pages 603-608
Ioanna I. Koukli, Evangelos G. Sarantonis and Antony C. Calokerinos

Abstract: Sample solution containing SO32- (0.30 to 3.0 µg mL-1) flowing at 2.00 mL min-1 was mixed with 0.5 mM Ce(IV) - 5 mM 3-(cyclohexylamino)propanesulfonic acid in 0.1 M H2SO4 (flow rate 1.60 mL min-1) immediately before entering a mirror-backed coiled-glass flow cell. The chemiluminescence produced by reduction of Ce(IV) was recorded by using a photomultiplier tube operated at -600 V. The detection limit was 0.02 µg mL-1 of SO32- and the coefficient of variation (n = 4) for 0.30 and 3.0 µg mL-1 of SO32- were 2.0 and 1.0%, respectively. The sampling rate was 50 h-. Nitrate, NO2-, PO43-, Fe(CN)64-, AsO2-, oxalate, I-, Cl-, Br- and some metal ions and alcohols interfered. Metabisulfite and S2- can also be determined by the above method. To determine SO2, sample solution containing SO32- (to give a final concentration. of 1.00 to 20.00 µg mL-1 of SO32-) was mixed with 25.00 mL of aqueous 0.04 M Na2HgCl4 and 10.00 mL of 43 mM sulfamic acid, and the volume was adjusted to 100 mL with water before proceeding as above. This latter method was modified for the determination of SO2 in air. Response was rectilinear over the range studied and the detection limit was 0.8 µg mL-1 of SO32-.
Sulfite Sulfur dioxide Chemiluminescence Interferences

"Determination Of Formaldehyde In Air By Flow Injection Using Pararosaniline And Spectrophotometric Detection"
Analyst 1989 Volume 114, Issue 11 Pages 1469-1471
Mar&iacute;a Pedrero Mu&ntilde;oz, F. Javier Manuel de Villena Rueda and Luis M. Polo D&iacute;ez

Abstract: Air (1 l min-1) was drawn through water (50 ml) for 40 min, and the solution was diluted to 100 mL. An aliquot (80 µL) was injected into a flow (0.4 mL min-1) of 0.31 mM pararosaniline - 0.24 M HCl, which was merged with 4.3 mM Na2SO3 (0.4 mL min-1) and passed through a mixing coil (30 cm x 0.7 mm). Detection was at 570 nm, and conventional and stopped-flow methods were used. The calibration graphs were rectilinear for 2 to 50 and 0.2 to 10 µg mL-1 of formaldehyde for the two modes, respectively, and corresponding sampling rates were 41 and 18 h-1. The detection limits were 1.2 and 0.1 µg mL-1, respectively, and the coefficient of variation (n = 10) were 2.1% for 30 µg mL-1 by the conventional method and 6.3% for 0.6 µg mL-1 by the stopped-flow method. Results were compared with those of the standard chromotropic acid method, and showed good agreement.
Formaldehyde Spectrophotometry Method comparison Stopped-flow

"Flow Injection Spectrofluorimetric Measurement Of Oxidants Formed By An Atmospheric Photochemical Reaction Using Naphthalene-2-thiol"
Analyst 1992 Volume 117, Issue 8 Pages 1339-1241
Tadao Sakai and Harumitsu Nishikawa

Abstract: Photochemical oxidants such as O3 and peroxyacetyl nitrates were determined in air by flow injection analysis with detection of the decrease in fluorescence, based on the reaction of I2 with naphthalene-2-thiol (I). The oxidants were collected in 0.06 M KI absorbent solution The carrier and reagent solution were aqueous 20 mM KI and 0.5 mM I in 1,2-dichloroethane, respectively, at a flow rate of 0.55 mL min-1. Samples containing up to 0.05 mM I2 were injected via a 6-way valve and passed to a 100 cm x 0.5 mm reaction coil. The fluorescence intensity was monitored at 362 nm (excitation 283 nm). The decrease in fluorescence was rectilinear in the range 0 to 1 µM of I2. The coefficient of variation was 1.0% for 5 µM-I2 in the absorbent solution, and the detection limit for photochemical oxidants was 2 ppb in 20 l of air. The sample throughput was 30 h-1. The method was applied to urban air, and interference from SO2 was reduced by the use of glass filter papers coated with CrO3 and H2SO4 before the absorbent solution A method to determine photochem. oxidants in air by flow injection with detection of the decrease in fluorescence, based on the reaction of I with naphthalene-2-thiol, was developed. The decrease in fluorescence was linear from 0-10 x 10^-6 mol/L of I. The relative standard deviation was <1.0% at the 5 x 10^-6 mol/L level of I in the absorbent solution; the detection limit for photochem. oxidants in air was 2 ppb (v/v) in a 20 L sample of air. The sample throughput was 30/h.
Fluorescence Photochemistry Interferences

"Rapid And Sensitive Assay For Some Protease Enzymes Using A Fluorisubstrate-immobilized Bioreactor"
Analyst 1995 Volume 120, Issue 7 Pages 1949-1952
Lian X. Tang, Frederick J. Rowell and R. H. Cumming

Abstract: A flow injection method for the assay of some protease enzymes is described. The sample (20 µL) was injected into a carrier stream (0.2 ml/min) of buffer (Tris or PBS containing Tween 20) of pH 9 and passed through a column of fluorescein-labelled porcine thyroglobulin immobilized on silanized glass beads (preparation described). The fluorescence intensity of the solution emerging from the column was measured at 518 nm (excitation at 490 nm). Calibration graphs were linear from 2-50 ng of subtilisin and trypsin and from 20-200 ng of esperase and alcalase. The detection limit for subtilisin was 0.15 ng. The RSD (n = 12) for 5 ng of subtilisin was 0.8%. The method can be used to monitor air in industries using the enzymes.
Enzyme, protease Subtilisin Trypsin Enzyme, esperase Alcalase Fluorescence Immobilized enzyme Glass beads

"Flow Injection Method For The Determination Of Arsenic(III) At Trace Levels In Alkaline Media"
Analyst 1996 Volume 121, Issue 10 Pages 1387-1391
Joseph H. Aldstadt and Alice F. Martin

Abstract: Sample (100 µL) was injected into a carrier stream (0.75 ml/min) of 10 mM NaOH in a flow injection (FI) system (schematic shown) and transported to a wall-jet flow-through cell. On reaching the cell, the flow was stopped and the sample zone was analyzed for As(III) by constant-current potentiometric stripping analysis at a Au disc working electrode: a depoon potential of -1050 mV vs. Ag/AgCl was applied for 180 s after which stripping was effected by applying a current of +0.1 µA; As(III) was determined by measuring the peak potential at -475 mV. The calibration graph was linear for 0.1-50 µg/l As(III), the detection liwas 0.21 µg/l and the RSD (n = 8) was ?. The method was applied to the indirect determination of Lewisite, a chemical warfare agent which is difficult to measure in the environment because it rapidly decomposes to form its geminal diol 2-chlorovinylarsonous acid (I). Base hydrolysis of I yielded arsenious acid for detection by FI-potentiometry.
Arsenic(3+) Lewisite Potentiometric stripping analysis Electrode Electrode Potentiometry Stopped-flow Indirect

"Determination Of Sulfite In Sugar And Sulfur Dioxide In Air By Chemiluminescence Using The Ru(bipy)3(2+)-KBrO3 System"
Analyst 1998 Volume 123, Issue 10 Pages 2109-2112
Fengwu Wu, Zhike He, Hui Meng and Yun'e Zeng

Abstract: A chemiluminescence (CL) detection method for the determination of sulfite using the reaction of Ru(bipy)32+ (bipy = 2,2'-bipyridyl)-SO32--KBrO3 is described. The concentration of sulfite is proportional to the CL intensity in the range 2.5 x 10^-8-9.5 x 10^-5 mol l-1. The limit of detection is 3.8 x 10^-9 mol L-1 and the relative standard deviation is 4.6% for 5 x 10^-5 mol L-1 sulfite solution with nine repeated measurements. This method was successfully applied to the determination of sulfite in sugar and sulfur dioxide in air by using triethanolamine as the absorbent material.
Sulfite Sulfur dioxide Chemiluminescence

"Simultaneous Determination Of Atmospheric Nitric Acid And Nitrous Acid By Reduction With Hydrazine And Ascorbic Acid With Chemiluminescence Detection"
Analyst 1992 Volume 117, Issue 5 Pages 883-887
Yukio Kanda and Masafumi Taira

Abstract: A continuous-flow system for the simultaneous determination of atmospheric HNO3 and HNO2 was developed, consisting of two sets of dual-channel flow systems: one to measure total HNO3-HNO2 and the other to measure HNO2. HNO3 and HNO2 are continuously stripped from the atmosphere into a NaOH solution by drawing the air sample and the solution through a glass coil. NO3- is reduced with hydrazine sulfate in the presence of Cu2+ to NO2-, which is then reduced to NO with an ascorbic acid solution; the NO is detected by a chemiluminescence NOx analyzer. This measurement system can also determine HNO2, thus giving the total concentration. of HNO3 and HNO2. The measurement system without the N2H4 reduction procedure determines HNO2 alone. The concentration of HNO3 is determined by the difference between the two measurements. Of the common pollutants, NO2 and peroxyacetyl nitrate showed positive interferences. To correct for these positive interferences, each of the measurement systems utilizes a dual flow system and a dual-channel NOx analyzer.
Nitric acid Nitrous acid Chemiluminescence Interferences Redox Differential detection

"Development Of A Proposed International Standard For Determining Arsenic In Workplace Air Using Hydride Generation Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1994 Volume 9, Issue 3 Pages 273-280
Robert D. Foster and Alan M. Howe

Abstract: Air was sampled on a cellulose ester membrane filter and paper back-up pad previously conditioned with 1 M Na2CO3 in aqueous 5% glycerol. The exposed filters were treated at 175°C with 5 mL of concentrated HNO3 and 1 mL of concentrated H2SO4, the volume was reduced to 1 ml, 2 mL of H2O2 was added after cooling, and the mixture was heated until SO3 evolution ceased. The residue was dissolved in 10 mL of water, and 5 mL aliquots were treated with 12.5 mL of concentrated HCl and 2.5 mL of 10% KI solution and then with a stream (5 ml/min) of 0.2-2% NaBH4 solution in 0.1 M NaOH. As was determined at 197.2 or 193.7 nm (calibration graphs linear for 0-50 and 0-25 ng/ml of As, respectively) in both flow injection (FI) and continuous-flow (CF) systems. For 4.8-96 µg of As added on-filter, recoveries were >98.8% for both systems. For 10^-40 ng/ml of As, RSD of 1 and 3% were obtained for the CF and FI systems, respectively, at 197.2 nm. The limits of detection and determination were 0.3 and 1 ng/ml at 197.2 nm. Preliminary results from an inter-laboratory study are discussed.
Arsenic Spectrophotometry Detection limit Cellulose ester

"Sample Flow Velocity And Low Level Sodium Ion Measurement With The Glass Electrode"
Anal. Chem. 1975 Volume 47, Issue 13 Pages 2307-2309
Edgar L. Eckfeldt and William E. Proctor Jr.

Abstract: The accuracy is increased and time and volume of solution required for anal. are decreased when an insert is placed in the sensor bulb portion of a sodium [7440-23-5] ion analyzer to increase the flow velocity of the sample solution passing the sensor bulb surface. By this procedure the flow rate is decreased from 150 to <10 ml/min and as little as 0.1 ppb Na can be determined in water [7732-18-5].
Sodium Electrode Theory

"Flow Injection Analysis Based On Two Consecutive Reactions At Gas-solid Interface For Determination Of Bromine And Chlorine"
Anal. Chem. 1980 Volume 52, Issue 13 Pages 2062-2066
S. M. Ramasamy, M. S. A. Jabbar, and Horacio A. Mottola

Abstract: Repetitive determinations of bromine and chlorine gases by a kinetic-based procedure, an adaptation of flow injection analysis, are described. The determination is based on monitoring the transient signal resulting from two consecutive reactions taking place at a gas-solid interface. The reaction responsible for a signal increase is that of X, and α-naphthoflavone [formation of a 1:l "contact charge transfer"- adsorption complex] leading to formation of a red-brown color. Signal return to base line is due to a slower, simultaneous, combination of two processes: spontaneous decomposition of the transient complex and reaction of the color complex with As(III) in which α-naphthoflavone is regenerated and X2 Is reduced to X-. All these reactions take place at the surface of a filter paper on which a layer of dried reagent mixture has been deposited. The course of the reaction is followed by transmittance spectrophotometry. The overall procedure allows performing about 70 determinations per filter paper unit at a rate of 100-120 determinations/h at parts per million levels.
Bromine Chlorine Spectrophotometry Closed loop Kinetic

"Repetitive Determinations Of Sulfur Dioxide Gas In Air Samples By Flow Injection And Chemical Reaction At A Gas-liquid Interface"
Anal. Chem. 1982 Volume 54, Issue 2 Pages 283-286
S. M. Ramasamy and Horacio A. Mottola

Abstract: Repetitive processing of air samples for SO2(g) determination In a continuous-flow system is presented. Determination Is based on the reaction of SO2 with di-p-hydroxo-bis[bis(1,l0-phenanthroline)iron(III)], the dimer of ferriin, at a gas-liquid Interface. The performance of an open tube coli reactor, a single-bead string reactor, and a midget impinger setup is discussed and compared. The proposed methodology allows determination of SO2. In the 0.5-15.0 ppm (v/v) range with relative standard deviations of 2-4% (for 10 repetitive determinations). The main reagent was electrochemically regenerated by controlled potential electrolysis allowing the use of a closed-loop system. The number of determinations per hour are 20 with the midget impinger, 40 with the open tube coll reactor, and 50 with the single-bead string reactor.
Sulfur dioxide Spectrophotometry Closed loop Open tubular reactor Single bead string reactor

"Continuous Atomic-spectrometric Measurement Of Ambient Levels Of Sulfur Dioxide In Air By Mercury-displacement Detection"
Anal. Chem. 1982 Volume 54, Issue 9 Pages 1490-1494
Geoffrey Marshall and Derek Midgley

Abstract: The analyticai atomic spectrometric technique of mercury displacement detection has been adapted so that sulfur dioxide can be determined at natural background levels in ambient air on a continuous basis with a 90% response time of 1-2 min. Sample air is drawn Into the reaction vessel containing mercury( I) ion reagent and any sulfur dioxide present reacts to form elemental mercury which is measured, after being swept out of the solution by the same flow of sample alr, by a mercury vapor detector. Reagent is continuously pumped through the analyzer and the instrument is calibrated with a permeation tube calibrator. The apparatus has a linear concentration range up to 100 ppb sulfur dioxide and a detection limit of approximately 0.2 ppb sulfur dioxide; this is much lower than can be obtained with existing commercial instruments. The apparatus is very precise and 6, 11, and 20 ppb sulfur dioxide can be measured with coefficients of variation of 1-2 % ,
Sulfur dioxide Spectrophotometry

"Trace Determination Of Aqueous Sulfite, Sulfide And Methanethiol By Fluorimetric Flow Injection Analysis"
Anal. Chem. 1986 Volume 58, Issue 13 Pages 2839-2844
Purnendu K. Dasgupta and Huey Chin Yang

Abstract: Flow injection analysis procedures involving merging streams or membrane-based reagent introduction have been developed for the fast analysis (24 samples h-1) of stabilized SO32-, S2- and methanethiol anions based on the reaction with N-(9-acridinyl)maleimide in aqueous 50% DMF to form a fluorescent product. The preservation of the anions in buffered formaldehyde and oxalohydroxamic acid stabilizers has been studied. Detection limits were 0.04, 0.60 and 0.80 µM, respectively, for SO32, S2- and methanethiol and, under favourable conditions, differential determination was possible. Negative interference from, e.g., formaldehyde was masked by CN-. The method was developed for analysis of air.
Sulfide Sulfite Methanethiol Fluorescence Interferences Membrane reagent introduction

"Electrochemical Determination Of Sulfur Dioxide In Air Samples In A Closed-loop Flow Injection System"
Anal. Chem. 1987 Volume 59, Issue 4 Pages 666-670
Angel Rios, M. D. Luque de Castro, Miguel Valcarcel, and Horacio A. Mottola

Abstract: The method involved injection of the gaseous sample (198 µL) into a carrier solution (pH ~4.5) containing ~1 mM di µ-hydroxybis[bis-(1,10-phenanthroline)]iron(III)(I) (flow rate 1.2 mL min-1, total volume 100 ml). After reaction at the gas - liquid interface at 50°C in the mixing coil (length 125 cm), the extent of reduction to ferroin(II) was amperometrically monitored at 0.964 V vs. silver - AgCl, with a carbon-paste working electrode and a vitreous-carbon auxiliary electrode. Regeneration of I was accomplished in the closed loop system by electrochemical oxidation of II. By application of a continuous-flow/stopped-flow operation (stop time 30 s), SO2 was determined at the 5.0 ppm level with a coefficient of variation (n = 11) of 3.2%; 25 samples could be analyzed in 1 h. By pretreatment of the carbon-paste electrode with Triton X-100, a similar detection limit was achieved with continuous-flow operation, at a rate of 35 samples h-1.
Sulfur dioxide Amperometry Electrode Closed loop Heated reaction Stopped-flow Tecator Triton X Surfactant

"Continuous Monitoring Of Ambient Ammonia With A Membrane Electrode-based Detector"
Anal. Chem. 1987 Volume 59, Issue 19 Pages 2345-2350
David M. Pranitis and Mark E. Meyerhoff

Abstract: A novel detection system suitable for the direct and continuous measurement of atmospheric ammonia levels in the 0.4-260 ppbv range is described. In the proposed system, an appropriate buffer reagent flows through a narrow-bore gas-permeable "sniffer" tube and on to a flow-through ammonium- selective membrane electrode. The ammonium activity detected by the electrode In the reagent stream is directly proportional to the gas-phase ammonia concentrations surrounding the sniffer tube. The detection range of the system can be varied merely by changing the flow rate of the reagent buffer and/or the length of the sniffer. No direct potentiometric response to other atmospheric gases (CO,, NO,, SO,, N,) is observed, although the presence of certain acidic gases appears to diminish the amount of free gaseous ammonia. It is shown that under optimized operating conditions, the system can readily detect small fluctuations In room-air ammonia levels which are measured to be In the 2-10 ppbv range.
Ammonia Electrode

"Chemiluminescent Method For Continuous Monitoring Of Nitrous Acid In Ambient Air"
Anal. Chem. 1990 Volume 62, Issue 19 Pages 2084-2087
Yukio Kanda and Masafumi Taira

Abstract: Air is drawn through a Teflon filter at 2 l min-1, mixed with 5 mM Na2CO3 (0.2 mL min-1) and passed through a ten-turn stripping coil (illustrated). The Na2CO3 scrubbing solution is reduced with 0.1 M ascorbic acid - 0.05 M H2SO4 and the mixture is passed into a gas - liquid separating coil consisting of microporous PTFE tubing inside a silicone tubing sheath (illustrated). The NO evolved diffuses through the microporous separating coil and is swept in a stream of NO-free air into a chemiluminescent NOx analyzer.. Interference by NO2 and peroxyacetyl nitrate are corrected for with use of a dual channel measurement system (diagram given). The calibration graph was rectilinear for 0.21 to 8.5 ppb of HNO2 and the limit of detection was 0.11 ppb. The method has been applied in the determination of ambient HNO2 and HNO2 produced by synchrotron radiation in a high-energy electron storage ring.
Nitrous acid Chemiluminescence Interferences Calibration Gas phase detection Phase separator Teflon membrane

"Hematin As A Peroxidase Substitute In Hydrogen Peroxide Determinations"
Anal. Chem. 1992 Volume 64, Issue 5 Pages 517-522
Genfa Zhang and Purnendu K. Dasgupta

Abstract: Various Mn - porphine complexes and hematin were examined as substitutes for horseradish peroxidase in the fluorimetric determination of H2O2. Hematin with p-cresol as substrate was an inexpensive alternative having comparable properties with reactions and fluorescence measurements being carried out in the same ammoniacal buffer. Hematin achieved a limit of detection of 5 nM-H2O2 in a flow injection system and was also employed in to the determination of H2O2 and alkyl peroxides in air, after separation by chromatography. The method has applications in clinical analysis. Hematin can substitute for horseradish peroxidase (HRP) as the catalyst in the determination of hydrogen peroxide using phenolic substrates such as p-hydroxyphenylacetate or p-cresol. Although the peroxidatic activity of hematin from bovine blood is not as great as HRP in terms of unit iron content, the activity per unit weight is substantially greater. Hematin is 500 times less expensive than HRP per unit peroxidatic activity. In hematin-catalyzed systems, reaction development and fluorescence measurement can both be conducted optimally in the same ammoniacal buffer. Hydroxyalkyl hydroperoxides are rapidly hydrolyzed to H2O2 at this pH and are also determined. On the other hand, for methyl hydroperoxide, hematin exhibits only approximately 10% of the sensitivity exhibited by HRP. Hematin is significantly more stable in solution than HRP. The use of hematin as catalyst and p-cresol as the substrate leads to a particularly inexpensive and sensitive system, permitting a limit of detection (LOD) of 7 nM H2O2 in a flow injection configuration.
Hydrogen peroxide Fluorescence Clinical analysis Immobilized enzyme Catalysis

"Continuous-flow Immunosensor For Detection Of Explosives"
Anal. Chem. 1993 Volume 65, Issue 24 Pages 3561-3565
James P. Whelan, Anne W. Kusterbeck, Gregory A. Wemhoff, Reinhard Bredehorst, and Frances S. Ligler

Abstract: Monoclonal antibodies specific for trinitrotoluene (TNT) were coupled to tresyl chloride-activated Sepharose 4B which was saturated with a solution of trinitrobenzenesulfonate and fluorescently-coupled cadaverine in borate buffer of pH 7.2 then packed into a Biocompatible Guard column (Upchurch, WA, USA). Samples containing TNT or dinitrotoluene (DNT) were injected into a stream (0.4 or 1 ml/min) of PBS of pH 7.4 containing 0.1% Triton X-100 and 12.5% ethanol for passage to the column where the fluorescence intensity was measured. The calibration graphs were linear from 10^-40 and 20-1200 ng/ml of TNT and DNT, respectively, at a flow-rate of 0.4 ml/min and as little as 0.25 ng of TNT could be detected. At a flow-rate of 1 ml/min, the calibration graph for TNT was linear from 20 to >1200 ng/ml, but the sensitivity was reduced 10-fold. The method was applied to air samples with satisfactory results (details given).
Trinitrotoluene 2,4-Dinitrotoluene Immunoassay Fluorescence Sensor Triton X Immobilized antibody Sepharose beads Surfactant

"Continuous Automated Determination Of Atmospheric Formaldehyde At The Parts Per Trillion Level"
Anal. Chem. 1994 Volume 66, Issue 4 Pages 551-556
Qijia Fan and Purnendu K. Dasgupta

Abstract: Air was passed through a Nafion membrane diffusion scrubber (40 cm x 0.8 mm o.d.) and gases diffused into an outer water jacket (0.12 ml/min). This aqueous solution was used as the carrier flow in a flow injection system, merging with a reagent containing 10 mg of 1,3-cyclohexanedione, 10 g of ammonium acetate and 4 mL of concentrated HCl in 100 mL of water (70 µL/min). The mixed stream was heated in a coil (300 cm x 0.46 mm i.d.) at 95°C, then cooled in a PTFE tube (30 cm x 0.3 mm i.d.) at 23°C. Fluorescence was measured with light from a phosphor-coated Hg pen lamp (370 nm) with a bandpass filter centred at 390 nm and with an emission filter of 50% transmission beginning at 460 nm. Calibration graphs in the aqueous phase were linear for 0.0136-13.6 µM-formaldehyde with a detection limit of 6 nM (9 parts per 1012 in air); the day-to-day RSD for calibration was 5%. The reaction with formaldehyde was 54% complete under these conditions and this increased the selectivity. The next most sensitive aldehyde, acetaldehyde was 300 times less sensitive. 1,3-Cyclohexanedione was used for automated near real-time fluorometric determination of atmospheric formaldehyde. Although previous literature reports indicate this reagent to be nonselective, adaptation of a fast flow injection technique that does not rely on the completion of the reaction provided a method with a selectivity factor of >300 for HCHO over its nearest congener, CH3CHO. The system was optimized with respect to the reagent and scrubber liquid composition, reaction temperature, and pH. The limit of detection (LOD) in the aqueous phase is 6 nM (180 ng/L) HCHO for a 45 mL sample (270 fmol) with the linear dynamic range spanning >3 orders of magnitude, up to at least 14 mM. The mean relative standard deviation in the 14 nM-14 mM range is 3. Gas-phase measurements utilized a Nafion 811 hydrophilic membrane tube based diffusion scrubber with water as the scrubbing liquid carrier. At a sampling rate of 1.4 L/min, the LOD for gas-phase HCHO is 9 pptrv. The mean rsd in the 0.07-110 ppbv range is 1.5. Copyright 1994, American Chemical Society.
Formaldehyde Spectrophotometry Hydrophilic membrane Nafion membrane Linear dynamic range

"Electrochemical Detection Of Trace Hydrogen Sulfide In Gaseous Samples By Porous Silver Electrodes Supported On Ion-exchange Membranes (solid Polymer Electrolytes)"
Anal. Chem. 1995 Volume 67, Issue 2 Pages 318-323
Gilberto Schiavon, Gianni Zotti, Rosanna Toniolo, and Gino Bontempelli

Abstract: A highly sensitive and fast-responding electroanalytical sensor for the determination of hydrogen sulfide in gaseous atmospheres is described which eliminates oxygen interferences. It consists of a porous silver working electrode (facing the sample) supported on one face of an ion-exchange membrane, which serves as a solid polymer electrolyte. The other side of the membrane faces an internal electrolyte solution containing the counter and reference electrodes. The performance of this sensor has been tested for the electroanalysis of H2S by amperometric monitoring, cathodic stripping measurements, and flow injection analysis. In all cases, the device displays a high current sensitivity and a low background noise, so that quite low detection limits (45 ppb v/v, 0.07 ppb v/v, and 3.7 x mol in amperometric, cathodic stripping, and flow injection measurements, respectively) are estimated for a signal-to-noise ratio of 3. The responses are found to be characterized by both a good reproducibility and a linear dependence on the concentration of H2S over fairly wide ranges, as well as by a short response time (ca. 0.5 s to attain a 95% response). This fast response time arises from the lack of a gas-permeable membrane and direct gas contact to the triple interphase among the gaseous an-, the porous working electrode, and the solid polymer electrolyte. The absence of any effect due to the most important potential interfering species and the possibility of adopting such a device for the direct detection of H2S in ambient air and for industrial hygiene measurements are discussed.
Hydrogen sulfide Amperometry Electrode

"A Pulse Amperometric Sensor For The Measurement Of Atmospheric Hydrogen Peroxide"
Anal. Chem. 1996 Volume 68, Issue 13 Pages 2062-2066
Huiliang Huang, Purnendu K. Dasgupta, Zhang Genfa, and Joseph Wang

Abstract: The sensor was constructed using two sections of Nafion tubing over a Ag wire with a 1 mm gap. The exposed Ag in the gap was electrochemically chloridized for 5 min in 0.1 M HCl to form a Ag/AgCl reference electrode. Pt and Pt/30% Rh wires were coiled round the Nafion tubing forming counter and working electrodes, respectively. The assembly was placed diagonally in PTFE tubing (15 mm x 2.5 mm i.d.) with the Ag wire protruding at each end. PTFE inlet and outlet tubes (0.6 mm i.d.) were inserted and the unit was encased in epoxy. The electrode was maintained at 0.3 V vs. Ag/AgCl, cleaned for 2 s at 0 V and pulsed to 0.8 V for amperometric measurement of H2O2. In FIA with 1 mM HCl as carrier solution at 1.5 ml/min, calibration graphs were linear for 0.2-4 µM-H2O2 with a detection limit of ~e;30 nM. The sensor was used with a Nafion membrane diffusion scrubber (cf. Atmos. Environ., 1991, 25A, 2717) for the measurement of atmospheric H2O2. The H2O2 collected was absorbed in 1 mM HCl for 4-10 min. A valve was opened to allow the scrubber liquor to flow-through the sensor cell. Calibration graphs were linear for 0-2 ppbv H2O2 with detection limits of 0.24 ppbv and 0.11 ppbv for pre-concentration times of 4 and 9 min, respectively. Results obtained agreed well with those obtained using a fluorimetric technique.
Hydrogen peroxide Electrode Amperometry Sensor Nafion membrane Preconcentration

"Methods For The Determination Of Inorganic Anions. 1. Spectrophotometric Trace Determination Of Chloride In Air, Water And Technical Products In The Iron(II) - Mercury - TPTZ System. Manual, CF And Flow Injection Analysis Methods"
Fresenius J. Anal. Chem. 1983 Volume 315, Issue 3 Pages 197-200
Bernd R&ouml;ssner und Georg Schwedt

Abstract: The application of the Fe(II)/Hg-tripyridyl-s-triazine system for the photometric trace analysis of chloride in the range of 10 g/l to 10 mg/l is shown. The improvement of the method for optimum results leads in the continuous-flow-technique to a detection limit of 5 g/l. A manual procedure for the range of 1-10 mg/l is also described. As examples for application, determinations of chloride in natural waters, p. a. salts, in a bitumen sample and in air are described.
Chloride Spectrophotometry Method comparison

"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 Spectrophotometry Cellulose Gas diffusion Membrane Method comparison

"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.
Gas diffusion Membrane Laminar flow

"A Continuous-flow Instrument With Flow Regulation And Automatic Sensitivity Range Adaptation For The Determination Of Atmospheric Hydrogen Sulfide"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 1 Pages 27-32
W. Jaeschke Contact Information, H. Schunn and W. Haunold

Abstract: A continuous-flow instrument (schematic of experimental set-up given) was developed for atmospheric H2S concentrations from 0.138-17.5 µg/m3. The flows were regulated by flow sensors connected to pumps via a feedback circuit. The instrument operates in two sensitivity ranges, viz., high and low. In the presence of low H2S concentrations (1.75 µg/m3) the instrument runs with low flow rate (0.37 ml/min) in high H2S concentrations (1.75 µg/m3) the pumps switch to a higher flow rate (1.13 ml/min) ensuring a linear quenching signal. The instrument was tested during field measurement in the tropics.
Hydrogen sulfide Gas phase detection Quenching

"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 Coulometry Gas diffusion Optimization

"Chemiluminescence Determination Of Sulfite In Sugar And Of Sulfur Dioxide In Air Using The Tris(2,2 '-bipyridyl)ruthenium-KIO4 System"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 7-8 Pages 566-570
F. Wu, Zhike He, H. Meng, Liangjie Yuan, Xiaoyan Li, Yun'e Zeng

Abstract: The chemiluminescence (CL) detection for the determination of sulfite using the reaction of Ru(bipy)(3)(2+)(bipy=2,2'-bipyridyl)-SO32--KIO4 is described. The concentration of sulfite is proportional to the CL intensity from 1.0 x 10^-7 to 1.0 x 10^-4 mol/L. The limit of detection is 2.0 x 10^-8 mol/L and the relative standard deviation is 4.4% for a 2 x 10^-5 mol/L sulfite solution (n = 9). This method has successfully been applied to the determination of sulfite in powdered sugar (sucrose) and of sulfur dioxide in air by using triethanolamine (TEA) as absorbent material.
Sulfite Sulfur dioxide Chemiluminescence

"Determination Of Organolead Compounds And Of Chromate Beside Chromium(III)"
Microchim. Acta 1992 Volume 109, Issue 1-4 Pages 137-140
Bernd Neidhart and Christoph Tausch

Abstract: The pre-concentration. and determination of ionic alkyl-lead compounds in surface water and human urine and tetra-alkyl-lead compounds in ambient air are described. Preconcentration and cleanup steps were followed by HPLC separation. Ionic species were pre-concentrated by solid-phase extraction; detection was performed online. The alkyl-lead species were eluted from the HPLC column, partially de-alkylated by iodine solution to form dialkyl-lead species and detected as PAR [4-(2-pyridylazo)resorcinol] complexes after the reduction of excess iodine with thiosulfate and adjustment to pH 9 to 10. Difficulties in the validation of trimethyl-lead and dimethyl-lead in some matrices are discussed. A Cr(VI) speciation method consisting of selective biosampling using human erythrocytes and gas-furnace AAS and reversed flow injection analysis is described.
tetraalkyllead Chromium(VI) Spectrophotometry Reverse Speciation

"Detection Of Sulfur-dioxide Using A Piezoelectric Quartz-crystal Microbalance"
Anal. Lett. 1997 Volume 30, Issue 12 Pages 2159-2174
Orliney M. Guimar&atilde;es; Jos&eacute; F. Andrade; Denise P. Ruys

Abstract: Sulfur dioxide was detected and determined in air by a piezoelectric quartz crystal sensor coated with 4-aminoantipyrine/1-hydroxyetil-2-heptadecenyl imidazol (amine 220) solution (1:1 v/v in chloroform). The analytical response curve is linear over the concentration range from 0.70 to 5.0 ppm of SO2. Good linearities (r = 0.9990, 0.9995 and 0.9968) and sensitivities (18.0, 33.4 and 50.7 Hz/ppm) were found, respectively for exposure times of 30, 60 and 90 seconds. The sensor can be used for more than six months without loss in sensitivity and presented good reversibility and reproducibility. Among some possible interferents tested, only nitrogen dioxide and moisture caused major frequency changes. 18 References
Sulfur dioxide Microbalance Interferences Gas phase detection

"Carbon Paste Electrode Chemically Modified By Direct Admixing Of Tris-(4,7-diphenyl-1,10-phenanthroline)iron(II)"
Electroanalysis 1989 Volume 1, Issue 2 Pages 155-160
Christopher J. Hynes, Mojtaba Bonakdar, Horacio A. Mottola*

Abstract: The electrodes (radius 3 mm) were prepared by mixing tris-(4,7-diphenyl-1,10-phenanthroline)iron(II) perchlorate (I) with graphite and acetone and then adding light mineral oil. A typical paste contained 10% of I, 56% of graphite and 34% of oil. Cyclic voltammetry at the electrode with use of a BAS-100 electrochemical analyzer gave one stable Fe(III)-reduction peak at ~+1.0 V vs. Ag - AgCl and one oxidation peak at ~+1.2 V, which disappeared with successive cycling; both peaks were almost independent of pH in the range 1 to 5. The electrode (which has a low rate of loss of I by leaching) was applied in the determination of NO2 from its electrocatalytic oxidation of I in a continuous-flow system; typical coefficient of variation (n = 10) at 15 ppb (v/v) of NO2 in air were ~5%.
Nitrogen dioxide Electrode Electrode Voltammetry Apparatus Detector

"Studies With A Sulfite Oxidase-modified Carbon Paste Electrode For Detection/determination Of Sulfite Ion And Sulfur Dioxide(g) In Continuous-flow Systems"
J. Electroanal. Chem. 1990 Volume 284, Issue 2 Pages 323-333
P. Abu Nader, S. Sagrado Vives* and Horacio A. Mottola

Abstract: Modification of carbon paste electrodes by direct admixing of the enzyme sulfite oxidase from chicken liver [EC] that was previously immobilized on crosslinked agarose gels activated with 1,1'-carbonyldiimidazole and their amperometric peformance in continuous-flow systems are described. The effect of different experimental parameters in the selective detection/determination of sulfite ion in aqueous solutions and S02(g) in air is reported. Hexacyanoferrate ions, used as redox mediators, cannot be incorporated directly (after electrostatic immobilization) into the electrode but their utilization is possible via two alternatives: (a) directly in solution, or (b) immobilized on poly(4-vinylpyridine) but incorporated as a solid reservoir that 'bleeds' the redox mediator slowly into the carrier stream. The second alternative offers some advantages for detection/determination of sulfite ion and SO2(g) at ppb levels.
Sulfite Sulfur dioxide Electrode Electrode

"A Critical Comparison Of Different Solid Supports To Develop Room-temperature Phosphorescence Sensing Phases Of Air Moisture"
Sens. Actuat. B 1997 Volume 38, Issue 1-3 Pages 103-109
J. M. Costa-Fern&aacute;ndeza, A. Sanz-Medela,* and M. E. D&iacute;az-Garc&iacute;aa

Abstract: The effects were studied of different solid supports, viz., Dowex 1X2-200 anion-exchange resin beads, Bio-Rex AG 1-X8 anion-exchange membrane, and an inorganic sol-gel matrix, on the detection of moisture in Ar and air based on the quenching effect of water on the room-temperature phosphorescence of the chelate complex formed between 8-hydroxy-7-iodo-5-quinolinesulfonic acid and Al(III). With use of resin beads or anion-exchange membrane as support it was necessary to employ room-temperature phosphorescence lifetime measurements owing to swelling of the support in the wet gas stream. With resin beads and anion-exchange membrane supports the detection limits were 2.1 and 1.4% r.h., respectively, and response was linear up to 100% r.h. For a moisture content of 28.4% r.h. the respective RSD were 2.8% and 4.2% (n = 5). When the chelate was immobilized on a sol-gel prepared by hydrolysis of a mixture of tetramethoxysilane and methyltrimethoxysilane, the limit of detection was 0.09% r.h., and response was linear up to 30% r.h. in the continuous sensing mode, but the analytical range was 0.35-80% r.h. when a flow injection technique was used. At the 8% r.h. level the RSD were 3.2% and 2% respectively (n = 5). Response times were 3-5 min.
Water Phosphorescence Column Complexation Membrane Sol-gel Dowex Biorex Resin Quenching

"Amperometric Microsensor Array With 1024 Individually Addressable Elements For Two-dimensional Concentration Mapping"
Sens. Actuat. B 1994 Volume 21, Issue 1 Pages 33-37
T. Hermesa, M. B&uuml;hnera, S. B&uuml;chera, C. Sundermeierb, C. Dumschatb, M. Borchardtb, K. Cammannb and M. Knollb, a

Abstract: The cited microsensor array (fabrication described) contained 32 rows and 32 columns of individual addressable amperometric cells on a Si substrate (30 mm x 30 mm). Each cell contained non-polarizable Ag/AgCl reference electrodes (40 µm x 80 µm) and Pt working electrodes of equal dimensions, connected to columns and rows, respectively. HEMA (2-hydroxyethylmethacrylate) was used as a gel electrolyte. Gaseous and biological applications of the sensor for the 2D mapping of O2 concentration profiles are discussed. The sensor response time was estimated at a few seconds, 60-70 s being required for measurement of the whole array. In dry air, the sensor lifetime was about 15 min and limited by the hydrogel. The open architecture of the measuring system should allow it to be used for a multitude of chemical analysis problems. Because of the short response times, the array is suitable for FIA applications and hence nearly real-time multiple analyte detection may be possible.
Oxygen Electrode Electrode Amperometry Sensor

"Gas-phase Chemiluminescence Detection Of Trace Arsenic In Environmental Water"
Anal. Sci. 1990 Volume 6, Issue 3 Pages 425-430

Abstract: The method involves conversion of As into AsH3, mixing the AsH3 produced with O3 and measurement of the resulting chemiluminescence. The apparatus used is illustrated schematically. For determination of total inorganic As, concentrated HCl was added to the sample to 2M, and for total As, the sample was treated with 15% NaOH - 5% K2S2O8 for 1 h at 80°C to 85°C, 40% KI - concentrated HCl for 20 min at room temp., and then 10% ascorbic acid before analysis. The method allowed determination of As at 1 ng mL-1. The method was applied to rain, seawater and condensed atmospheric moisture. Results were slightly higher than those obtained by flow injection analysis - AAS.
Arsenic Chemiluminescence Method comparison Volatile generation Volatile generation

"Ultra-rapid Fluorescence Assay For Cellulase Using A Substrate-immobilized Mini-bioreactor"
Anal. Proc. 1995 Volume 32, Issue 12 Pages 519-520
Lian X. Tang, Frederick J. Rowell and Robert H. Cumming

Abstract: Cellulose (1 g) was activated by the method of Hermanson et al. ('Immobilized Affinity Ligand Techniques', 1992, Academic Press, New York). The activated cellulose was washed with water and 0.1 M NaHCO3 buffer of pH 8.5 (buffer A) and treated with 15 mL ethylenediamine in buffer A (1:5) overnight. The amine-derived cellulose was washed with 0.5 M carbonate/hydrogen carbonate buffer of pH 9.5 (buffer B) and treated with 10 mL Lucifer Yellow (LY; 0.3 mg/ml buffer B) in the dark for 12 h. The LY-labelled cellulose was washed with water and 0.05 M sodium acetate buffer of pH 5 (buffer C) and a 500 µL portion was packed into a disposable plastic syringe tube and incorporated into an FIA system. Portions (20 µL) of cellulase (I) enzyme solutions (trypsin, pepsin and collagenase) and α-amylase were injected into stream of buffer C containing 0.1 M NaCl and 0.1% Tween 20 (2 ml/min) and the fluoresence intensity of the mixed solution was measured at 540 nm (excitation at 430 nm). The calibration graph was linear from 1-20 µg of I (0.5-10 iu/ml) and the detection limit was 0.84 µg. The RSD (n = 9) was 6.1% at 2 µg of I. The response time was ~e;30 s. The method was applied to monitor airborne levels of I in industries using the enzyme.
Enzyme, cellulase Fluorescence Cellulose Reactor Immobilized reagent

"Flow Injection Environmental Analysis. A Review"
Analusis 1985 Volume 13, Issue 4 Pages 147-159

Abstract: A review is presented, with 134 references. The basic flow injection analysis components and the various modes of flow injection analysis are described. Methods of determination of inorganic ions in various water samples are tabulated, and determination of inorganic air pollutants is briefly discussed.

"Rapid, Automated Analysis Of Carbon-13 And Oxygen-18 Of Carbon Dioxide In Gas Samples By Continuous-flow, Isotope Ratio Mass Spectrometry"
Biol. Mass Spectrom. 1991 Volume 20, Issue 11 Pages 724-730
S. J. Prosser, S. T. Brookes, A. Linton, T. Preston

Abstract: An automated continuous-flow system is described (diagram given). Breath is collected in either Vacutainers or Exetainers placed in an autosampler. The sample gas is flushed out of the container into a He flow which is passed through a drying tube containing MgClO4 and then to a GC column (18 in x 0.25 in) of Carbosieve-G operated at 60°C to 120°C. The carrier gas containing the separated CO2 is passed to the ion source of a mass spectrometer. The system is evaluated by determining isotope ratios of 13C:12C in breath CO2, 18O:16O in water, 18O:16O in breath CO2 contaminated with N2O.
Carbon-12 Carbon-13 Oxygen-16 Oxygen-18 GC Mass spectrometry Automation Carrier gas Heated reaction Isotope ratio

"Investigation Of Collecting Conditions For Determination Of Arsine In Working Environment Of Semi-conductor Manufacturing Process"
Bunseki Kagaku 1991 Volume 40, Issue 3 Pages 149-152
Koyama, M.;Chaki, S.;Yamamoto, M.;Kumamaru, T.

Abstract: Sample gas (3 l) was passed at 1 l min-1 for 30 min through an impinger, comprising a bent-type gas dispersion tube sintered with a porous glass plate (20 mm i.d.; 40 to 100 µm), containing 20 mL of 2% KMnO4 - 0.6% H2SO4 solution The absorbing solution was treated with 10 mL of 2.5% H2O2 - 0.6% H2SO4 solution and As was determined by flow injection analysis - hydride-generation AAS. Arsine was determined in the working environment from 8.7 to 420 µg m-3. Recovery was 95%.
Arsine Sample preparation Spectrophotometry

"Galvanic Gas Detector Using Polymeric Electrolyte Film For FIA Of Nitrogen Dioxide"
Bunseki Kagaku 1991 Volume 40, Issue 4 Pages T77-T81
Nagashima, K.;Yajima, I.;Hobo, T.

Abstract: The polymeric film was made by mixing acetonitrile with AgCF3SO3 and poly(ethylene oxide), casting the mixture on a disc (13 mm diameter x 1.1 mm thick) and evaporating the solvent. The working electrode (25 nm thick) was made by coating it with vaporized Au. The max. response appeared within 3 s, after a 2.6 mL sample was injected into the N carrier stream (40 mL min-1). Calibration graphs were rectilinear for 0.2 to 8 ppm of NO2; the coefficient of variation for 1.0 ppm of NO2 was ~3%. After 200 samples the response decreased by 15%.
Nitrogen dioxide Electrode Gas phase detection

"Successive Determination Of Sulfur Dioxide And Hydrogen Sulfide In Atmosphere By Using A Continuous-flow-type Analyzer Equipped With A Chemiluminescent Detector"
Bunseki Kagaku 1992 Volume 41, Issue 4 Pages 157-162
Ishii, M.;Miura, M.;Sato, J.

Abstract: Atmospheric SO2 is trapped in HgCl2 - NaCl solution and H2S is subsequently trapped in Zn(NH3)6(OH)2 solution; a diagram of the trap system is presented. The SO2 and H2S are successively swept from the trap and mixed with a stream of 2 µM-KMnO4 - 2 mM riboflavine 5'-phosphate, and the resulting chemiluminescence is detected with a cooled photomultiplier tube. The log-log calibration graphs were non-rectilinear; the detection limits for SO2 and H2S were 0.2 µM and 0.9 µM, respectively. The coefficient of variation (n = 3) for 2.23 µM SO2 and 2.23 µM H2S were 4.0 and 3.6%, respectively. The only interference was from Na2S2O3, which gave a chemiluminescence response equivalent to that of H2S. Successive determination of H2S and SO2 in the atmosphere was carried out using a flow analyzer equipped with a chemiluminescent detection system for excited SO2 after oxidation with KMnO4. The analyzer comprises the sample flow line with trap for SO2 and H2S and 2 reagent flow lines supplying KMnO4 solution and riboflavin phosphate solution The lower detection limit was 1.78 x 10^-7 M for SO2 and 8.92 x 10^-7 M for H2S, and the relative standard deviation was 4.0% for SO2 solution and 3.6% for H2S solutions at 2.23 x 10^-6 M. Na thiosulfate alone had a chemiluminescent response as large as that of H2S and no other interference was observed The results were in agreement with those obtained by conventional methods.
Sulfur dioxide Hydrogen sulfide Chemiluminescence Interferences Method comparison

"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 Spectrophotometry Gas diffusion Interferences

"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 Conductometry Microporous membrane Polyvinylidene difluoride Gas diffusion

"Measurement Of Low Concentrations Of Ammonia In The Atmosphere By Flow Injection Analysis"
Commun. Soil Sci. Plant Anal. 1991 Volume 22, Issue 17-18 Pages 1741-1752
Bristow, A.W.

Abstract: A method is described for the determination of NH3 in air above grazed pasture. Urine of known chemical composition was applied to a soil core sample, with a regulated flow of NH3-free air maintained across the surface. Volatilized NH3 was absorbed in 10 mM H2SO4, the solution was diluted with water and a portion (100 µL) was mixed in the coil (0.3 m x 0.5 mm) of a flow injection analyzer. with 0.4 M sodium salicylate, 0.00125 M sodium nitroprusside, 0.0045 M sodium dichloroisocyanurate, 0.35 M NaOH (all at 0.6 mL min-1) and 3 mM H2SO4 as carrier (0.8 mL min-1). The reaction coil (3.5 m x 0.5 mm) was heated at 70°C and detection was carried out at 655 nm. Peak height measurements gave a detection limit of 10 ppb NH3-N in solution for a working range of 0 to 1000 ppb, corresponding to an air concentration. of 4 µg m-3. The coefficient of variation was 1.11% and the response was rectilinear up to 15 ppm.
Ammonia Spectrophotometry Heated reaction

"Membrane-based Flow Injection System For Determination Of Sulfur(IV) In Atmospheric Water"
Environ. Sci. Technol. 1986 Volume 20, Issue 5 Pages 524-526
Purnendu K. Dasgupta and Vinay K. Gupta

Abstract: Atmospheric water was collected in buffered formaldehyde absorber solution (pH 4.8) and subjected to flow injection analysis. The sample was mixed with aqueous 50% NaOH in a passive cation-exchange membrane reactor and then mixed with pararosaniline - H2SO4 solution in a pressurized porous membrane reactor before determination by photometric detection at 580 nm. The limit of detection was 0.16 µM-S and up to 31 µM could be determined; the coefficient of variation was 2.5%.
Sulfur Ion exchange Spectrophotometry Membrane Reactor

"Analysis Of Atmospheric Ammonia And Particulate Ammonium By A Sensitive Fluorescence Method"
Environ. Sci. Technol. 1988 Volume 22, Issue 8 Pages 948-952
S. Rapsomanikis, M. Wake, A. M. N. Kitto, and Roy M. Harrison

Abstract: Atmospheric NH3 and particulate NH4+ were collected on H3PO4-impregnated Whatman 41 and PTFE filters, respectively, and the filters were extracted with water. The extracts were analyzed in a flow injection system by injecting the solution into the phthalaldehyde(I) eluent stream and measuring the fluorescence of the NH4+ - I moiety at 455 nm (excitation at 335 nm). Results correlated well with those obtained by the indophenol blue method; the detection limit was 204 ng m-3 for NH3 and 27 ng m-3 for NH4+. Air sampling with both filter packs and a denuder system was evaluated.
Ammonia Ammonium Fluorescence Method comparison

"Flow Injection Analysis With Chemiluminescence Detection Of Trace Hydrazine In Air"
Fenxi Huaxue 1997 Volume 25, Issue 3 Pages 263-266
Wu, Y.Y.;Zhao, F.;Geng, Z.;Chen, Z.G.;Liu, Q.G.

Abstract: Air was sampled by bubbling at 1 l/min for 2 h through an absorption solution of 2 M H2SO4. The solution was then adjusted to pH 5 with NaOH and diluted with water. A portion was injected into a stream of 0.6 mM KIO4 in 0.2 M NaOH which passed through a mixer (40 cm long) then merged with a stream of 0.9 mM luminol in 0.6 M NaOH prior to chemiluminescence detection. The calibration graph was linear from 10 ng/ml to 1 µg/ml hydrazine, the detection limit was 4 ng/ml and the RSD were The sampling frequency was 80/h. The detection limit in a 120 l air sample was 2 µg/m3 hydrazine.
Hydrazine Chemiluminescence Gas phase detection

"Flow Injection Analysis Of Formaldehyde And Sulfite Using The Oxidation Of P-phenylenediamine By Hydrogen Peroxide"
Int. J. Environ. Anal. Chem. 1993 Volume 53, Issue 3 Pages 195-203
T. P&eacute;rez-ruiz; C. Mart&iacute;nez-lozano; V. Tom&aacute;s; F. J. Carri&oacute;n

Abstract: A programmable stopped-flow FIA system was used. All mixing coils were 30 cm long and of 0.5 mm i.d., and the flow rate in each channel was 0.7 ml/min. To determine formaldehyde, a 120 l sample was injected into a stream of 0.2 M phosphate buffer of pH 6.5, which after passage through a mixing coil merged with a stream of 1 M H2O2 and, after passage through another mixing coil, with a stream of 15 mM p-phenylenediamine. After passage through a further mixing coil the flow was stopped for 1 min with the sample zone in an 18 l flow cell, wherein the increase in absorbance at 530 nm was measured. The calibration graph was linear for 3-300 mg/l of formaldehyde, the detection limit was 0.5 mg/l, and the RSD (n = 10) at 13.7 and 20.4 mg/l were 0.48 and 0.67%, respectively. A tenth-molar amount of Cu(II) or Mn(II) interfered. To determine sulfite, 120 l of 3.2 mM formaldehyde was injected into a stream of the sample solution, which passed through a reaction coil (200 cm x 0.5 mm i.d.) before merging with buffer, H2O2 and p-phenylenediamine streams and absorbance measurement as before. The graph was linear for 5-60 mg/l of sulfite, the detection limit was 1 mg/l, and the RSD (n = 10) at 9.2 and 38.3 mg/l were 0.85 and 0.56%, respectively. An equimolar amount of nitrite or Mn(II) interfered. Results for sulfite in wine agreed well with those obtained by the p-rosaniline method.
Formaldehyde Sulfite Spectrophotometry Redox Catalysis

"Measurement Of Atmospheric Formaldehyde Using A Drop Collector And In-situ Colorimetry"
Int. J. Environ. Anal. Chem. 1997 Volume 66, Issue 3 Pages 201-213
Pereira, E.A.;Dasgupta, P.K.

Abstract: A sensitive and affordable approach is described for the in-situ measurement of ambient formaldehyde. Air is sampled around a 100 µL aqueous drop containing 3-methyl-2-benzothiazoline hydrazone. After a desired period of sampling (typ. 5 min) and a waiting period of 10 min for the reaction to be completed, a second reagent (FeCl3) is added to the drop by means of a conjoined conduit. A blue product is formed and is read after an additional 10 min of reaction by a fiber-optic/light emitting diode based photodetector. A fresh drop is then formed and the process begins anew. As demonstrated here, the limit of detection is similar to 6.25 µg m-3 HCHO but can be significantly improved by using longer sampling times and a sampling rate higher than 100 mL min-1 used in most of this work. This is the first example of a chromogenic drop sensor that utilizes sequential reagent addition.
Formaldehyde Spectrophotometry Stationary drop Light emitting diode Optical fiber

"Recent Progress In Continuous-flow Isotope-ratio Mass Spectrometry"
Int. Lab. 1991 Volume 21, Issue 7 Pages 31-34
Preston, T.;Barrie, A.

Abstract: The cited technique (illustrated) is discussed with applications to clinical and environmental analysis; the analysis of CO2 in exhaled breath is described.
Carbon dioxide Clinical analysis Mass spectrometry Isotope ratio

"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

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 Amperometry Electrode Gas diffusion Goretex

"Piezoelectric Quartz Crystal Detection Of Benzene Vapor Using Chemically Modified Cyclodextrins"
J. Chem. Soc. Perkin Trans. 2 1988 Volume 1988, Issue 3 Pages 319-324
Colin S. I. Lai, Gwilym J. Moody, J. D. Ronald Thomas, David C. Mulligan, J. Fraser Stoddart and Ryszard Zarzycki

Abstract: 2,6-Per-O-methyl-β-cyclodextrin 3-perbenzoate(I), 2,6-per-O-(t-butyldimethylsilyl)-α-cyclodextrin(II) and 2,6-per-O-allyl-α-cyclodextrin(III) were prepared. The piezoelectric crystals are the 9-MHz AT-cut quartz type with either Au- or Ag-plated electrodes on both sides, and the crystals are coated with solution of I or III in acetone or II in CHCl3. The crystal is powered by a Weir 400 power supply set at 9 V DC, and the frequency is monitored by a Marconi type 2431A 200-MHz digital frequency meter. The detector is used in conjunction with flow injection analysis, in which the air sample (1 ml), containing benzene, is injected into an air stream, dried by passing through silica gel, and carried (20 mL min-1) through the crystal cell. The cyclodextrin derivatives interact with benzene producing a decrease in frequency of crystal oscillation; the decrease in frequency is related to benzene concentration. The detector was used for the detection of benzene over the range 0.08 to 400 mg l-1, and II-coated crystals were the most suitable. Selective detection of benzene was achieved in the presence of methane, propane, butane, acetylene, NH3, nitrobenzene and toluene.
Benzene Piezoelectric crystal Electrode Electrode Interferences

"Rapid PAH Determination In Urban Particulate Air Samples By HPLC With Fluorimetric Detection And Programmed Excitation And Emission Wavelength Pairs"
J. Chromatogr. Sci. 1995 Volume 33, Issue 4 Pages 181-185
M.N. Kayali, S. Rubio-Barroso, and L.M. Polo-Diez

Abstract: The air sample was collected with use of a high-volume MCV sampler and glass fiber Whatman GF/A filters (Clifton, NJ) at a flow rate of 30 m3/h for 24 h. The filters were sonicated with 50 mL CH2Cl2 for 20 min and centrifuged at 4000 rpm. The extraction was repeated with 50 mL CH2Cl2 and the combined extract was evaporated to 2 mL to remove solvent followed by a further reduction in volume to 0.5 mL under N2. The extract was cleaned up on a preconditioned (details given) activated silica gel column (30 m x 1 cm i.d.; 8 g). Elution was effected with 25 mL hexane followed by 40 mL hexane/CH2Cl2 (4:1); the solvent of the second fraction was removed via a rotary evaporator. The residue was dissolved in methanol and made up to 10 mL. Samples without clean up were filtered. Portions (20 l) of the solutions were analyzed on a 5 m Hypersil Green PAH column (10 cm x 4.6 mm i.d.) operated at 22°C with gradient elution (1 ml/min). Detection was by fluorescence (wavelengths tabulated). Calibration graphs were linear from 0.01-1.2 ng/l for 13 PAH and detection limits ranged from fluoranthene (0.012 pg/l) and 0.45 g/l (naphthalene). Results were compared with those obtained by GC.
Hydrocarbons, aromatic, polycyclic HPLC Fluorescence Post-column derivatization

"Determination Of Sulfur Dioxide In Air By Flow Injection Analysis - Colorimetry"
Shenyang Yaoxueyuan Xuebao 1989 Volume 6, Issue 4 Pages 35-39
Kong Zhang, Xu Xiaomian, Chen Lizhen, Guan Sumei

Abstract: The pararosaniline colorimetric method was modified to shorten the analysis time and improve the reproducibility. Sample or standard solution (120 µL) was introduced into a flow system (diagram presented) in a carrier stream (1.8 mL min-1) and reacted with a color reagent solution containing 1.2% ammonium sulfamate, 0.04% pararosaniline hydrochloride (I) and 0.2% formaldehyde solution The absorbance of the complex formed was measured at 560 nm. The calibration graph was rectilinear from 1 (detection limit) to 12 µg mL-1 of SO2. Recoveries (n = 5) were 99 to 102.3% and the coefficient of variation (n = 7) was 0.9%. Results agreed well with those obtained by the original method. The total analysis time was ~0.7 min.
Sulfur dioxide Spectrophotometry Method comparison

"Applications Of A Mercury-vapor Atomic-fluorescence Detector"
Spectroscopy 1991 Volume 6, Issue 7 Pages 39-41
Stockwell, P.B.;Grillo, A.C.

Abstract: The applications of an automatic Hg detector based on atomic fluorescence principles are described. The instrument can be used to detect Hg in aqueous media over a wide linear-dynamic range and was successfully applied to the determination of total, inorganic and organic Hg in aqueous environmental samples using automatic continuous-flow and flow injection modes (brief details and schematic diagrams given). In combination with a trapping system based upon adsorption - desorption of Hg on to Au-impregnated sand, the detector was also used to determine the Hg concentration. in air or gaseous samples for application in the analyzes of urban stack emissions and natural gas feedstocks on a static or continuous basis.
Mercury(II) Ethylmercury Methylmercury ion Phenylmercury Mercury Fluorescence Automation

"Reagentless Continuous-flow Method For Determination Of Aqueous Ozone With Thin-film Semiconductor And Application To An Advanced Water Treatment Plant"
Water Sci. Technol. 1991 Volume 23, Issue 10-12 Pages 1961-1968
T. Aoki*, H. Oguro*, K. Fujiyoshi** and M. Yamamoto**

Abstract: The aqueous ozone sample flowed (13 mL min-1) down a glass separator tube (20 cm x 8 mm) inclined at 30°C to the horizontal and was met by an ascending stream (50 mL min-1) of clean dry air. The ozone transferred to the air stream was monitored by a thin-film semiconductor (at 67°C) which measured changes in electrical conductivity. Signals were proportional to a concentration. of ozone >5 µg L-1 and the coefficient of variation at a level of 7.6 µg L-1 was 3.8%. Interference from H2O2, chloramine and dichloramine was completely eliminated and there was no significant interference from other species occurring in water.
Ozone Conductometry Heated reaction Interferences

"Flow Injection Determination Of Sulfur Dioxide In Air With Chromatomembrane Preconcentration"
J. Anal. Chem. 1996 Volume 51, Issue 8 Pages 820-823
L. N. Moskvin and V. V. Nikonorov

Abstract: A gaseous sample containing SO2 was passed through a chromatoconcentrator and the concentrated SO2 was absorbed in a solution of iodine in KI containing starch. The absorbance of the sorbent was determined with a flow-through photometric cell at 597 nm. The concentrator incorporated a porous PTFE membrane with 0.3-0.5 µm micropores and 100-200 µm macropores. The sorbent was a filtered solution containing 47.5 µM-I2, 0.01 M KI and 0.03% starch. The gas flow was 50 ml/min and the sorbent flow was 0.3 ml/min. The limit of detection of SO2 in the sorbent was 2 µM. Interference caused by H2S, CH3SH, (CH3)2S and NOx was similar to that found with other analytical methods.
Sulfur dioxide Spectrophotometry Chromatomembrane Interferences Teflon membrane Solid phase reagent Preconcentration

"An Automated Sampler For Collection Of Atmospheric Trace Gas Samples For Stable Isotope Analyses"
Agric. For. Meteorol. 2003 Volume 118, Issue 1-2 Pages 113-124
A. J. Schauer, C. -T. Lai, D. R. Bowling and J. R. Ehleringer

Abstract: Research focused on the isotopic composition of CO2 exchange between terrestrial ecosystems and the atmosphere has been historically constrained by the need for personnel to be present at remote field sites for sample collection. In practice, this has limited sampling frequency and duration, and potentially even biases sampling events to fair weather periods. We have developed an automated sampling system that can be installed and used for unattended collection of 100 mL air samples in remote areas. The sampler was designed with the primary goal of collecting samples for analysis of CO2 concentration and its isotopic composition in ecosystem-atmosphere flux research, but several other potential applications are also discussed.Laboratory tests examined potential artifacts associated with sampler components. These tests included evaluation of potential isotopic exchange between atmospheric CO2 and sampler component materials and the effects of sample exposure to these materials for up to 5 days and under a wide range of temperatures (10-50°C). Some of the rejected component materials influenced either CO2 mole fraction or CO2 isotopic content. Exposure of air at subambient CO2 concentrations to all sampler components in an intact system for 5 days resulted in a [CO2] value that was 0.9 µmol mol-1 higher than for an equivalent sample collected by the sampler but not stored. Associated exposure-induced errors in δ13C of CO2 were generally small, ranging between 0.03 and 0.17[permil] for 0 day versus 5 days exposure, respectively. These error values were within the sampling precision associated with a PreCon continuous flow mass spectrometer analysis. A more substantial exposure-induced error was observed for δ18O in CO2 (0.29 and 0.88[permil], respectively). The potential for isotopic exchange between CO2 and sampler components increased under a combination of elevated temperature and multiple-day storage treatments. These errors were small and of similar magnitude between 10 and 40°C, but unacceptably large at 50°C. Finally, we compared Keeling plots created with samples collected by the sampler with those collected simultaneously by a manual method and found no detectable differences between the two approaches. Based on these results, we conclude that sampler induced isotopic exchange for air samples held up to 5 days between 10 and 40°C is largely within the overall precision limits of a PreCon continuous flow mass spectrometer measurement.
Carbon dioxide Mass spectrometry Isotope ratio Apparatus Optimization Gas phase detection

"Flow-Injection Chemiluminescence Determination Of Formaldehyde With A Bromate-Rhodamine 6G System"
Anal. Sci. 2003 Volume 19, Issue 12 Pages 1643-1646
Baoxin Li, Meilin Liu, Zhujun Zhang And Chunli Xu

Abstract: In this paper, a novel flow-injection chemiluminescence (CL) system for the determination of formaldehyde is described. It is based on a strong enhance effect of formaldehyde on the weak CL emission of the reaction between potassium bromate and rhodamine 6G in a sulfuric acid medium. A possible mechanism for this CL reaction is proposed. A CL calibration graph was linear in the range of 0.8 - 200 µg L-1 and the detection limit was 0.3 µg L-1 (3s). The relative standard deviation was less than 3% for 10 µg L-1 formaldehyde (n = 11). The method has been applied to determine formaldehyde in the air samples.
Formaldehyde Chemiluminescence Optimization Interferences

"Kinetic Spectrophotometric Determination Of Formaldehyde In Fabric And Air By Sequential Injection Analysis"
Anal. Lett. 2004 Volume 37, Issue 12 Pages 2545-2555
Suling Feng, Jing Fan, Aijun Wang, Xingguo Chen, Zhide Hu

Abstract: A kinetic method for measuring formaldehyde by sequential injection analysis (SIA) with spectrophotometric detection was developed for the first time. The method was based on the inhibitory effect of formaldehyde on the ethyl green (EG)-sulfite reaction. The linear range for formaldehyde was 1.0-20.0 µg mL -;1; the detection limit was 0.020 µg mL -;1. The measurement rate was 130 sec, thus allowing to analyze 27 samples per hour, the total reagent consumption in a cyclical procedure is only 240 µL. The method was applied to the determination of formaldehyde in fabric and air, and compared with acetyl acetone spectrophotometric method.
Formaldehyde Spectrophotometry Sequential injection Method comparison Kinetic