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

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Well

Classification: Environmental -> water -> well

Citations 33

"Determination Of Bromide In Natural Waters By Flow Injection Analysis"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 453-457
Torbjörn Anfält and Sigrid Twengström

Abstract: The phenol red method with detection at 590 nm is used, optimum sensitivity being obtained at pH 5.2. Concentrations down to 2 µM can be measured. Interference in natural waters is mainly from NH4+, CN- and humic substances. A single reaction coil (60 cm x 0.7 mm) is used, and a simple procedure for the study of interfering species is described.
Bromide Spectrophotometry Interferences

"Chemical Oxygen Demand Determination In Well And River Waters By Flow Injection Analysis Using A Microwave Oven During The Oxidation Step"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 295-299
M. L. Balconi, M. Borgarello and R. Ferraroli*, F. Realini

Abstract: The sample (0.25 ml) is injected into water as carrier and, after mixing, the stream is treated with oxidizing solution prepared by adding dropwise, with vigorous stirring, 10 mL of aqueous 12% K2Cr2O7 to 300 mL of concentrated H2SO4 and diluting the cooled solution to 1 l with concentrated H2SO4. The resulting solution passes through a reaction coil (10 m) enclosed by a microwave oven operated at 180 W and then through a cooling coil and a de-bubbler before absorbance measurement at 445 nm. Under optimum conditions (described), the calibration graph is rectilinear for COD up to 100 mg l-1, and the detection limit is 1.5 mg l-1. The coefficient of variation was 2.1% (n = 20) at 40 mg l-1. Results obtained on well, river and canal water, sewage and food industry waste agreed with those by a standard method. A flow injection method based on the use of a microwave oven to maximize the rate of the oxidation step is described. The flow system consists of 2 lines (water as carrier and K dichromate-H2SO4 mixture as reagent), 3 coils, of which the intermediate one (wound around a special strong microwave absorber support) acts as reaction coil, a membrane degassing unit, and a spectrophotometric detector. Optimal parameters includes the oven capacity at 180 W, application range in 0-100 mg/L COD, relative standard deviation 2.12% at 40 mg/L COD, and detection limit 1.5 mg/L COD. Preliminary applications were made to well water, river water (with low COD levels), and wastewaters. The results obtained are in good agreement with those given by the manual reference method.
Chemical oxygen demand Spectrophotometry Microwave Method comparison Optimization Standard method

"Fluorimetric Flow-through Sensor For Aluminum Speciation"
Anal. Chim. Acta 1994 Volume 295, Issue 1-2 Pages 59-65
P. Cañizares and M. D. Luque de Castro*

Abstract: Water was injected into a 0.1 M NaCl carrier stream (1 ml/min) and merged with a reagent stream (1 ml/min) containing 0.025% salicylaldehyde picolinylhydrazone in 40% ethanol and 0.5 M acetate buffer of pH 5-5.5. After passage through a PTFE mixing coil (400 cm x 0.5 mm i.d.), the complex formed was retained on a layer of Sep-Pak C18 in the flow cell for fluorescence measurement at 468 nm (excitation 382 nm). The complex was desorbed to waste by 2 M HCl. All forms of monomeric aluminum except the hydroxy species reacted. Total monomeric Al was determined by direct injection as described. Non-labile monomeric Al was determined by injection as above, but the carrier stream passed through a column (5 cm x 3 mm i.d.) of Amberlite IR-120 plus to retain cationic species, the anionic and neutral species then merging with the reagent. Acid-reactive Al was determined by adjusting the sample to pH 1, after 1 h readjusting to pH 6, then as for total monomeric Al. Acid-soluble Al and labile monomeric Al were calculated by difference. Calibration graphs for total monomeric Al were linear for 10^-200 ng/ml with a detection limit of 3 ng/ml. The method was used to study the effect of organic ligands (oxalate, citrate, acetylacetone) on the distribution of Al species. The results of analyzes of bottled, tap, spring, well and river waters are reported.
Aluminum Spectrophotometry Fluorescence Sensor Speciation Amberlite

"Comparison Of The Analytical Capabilities Of An Amperometric And An Optical Sensor For The Determination Of Nitrate In River And Well Water"
Anal. Chim. Acta 1994 Volume 299, Issue 1 Pages 81-90
Margaret A. Stanley, Joe Maxwell, Mairead Forrestal, Andrew P. Doherty, Brian D. MacCraith, Dermot Diamond and Johannes G. Vos

Abstract: The analysis of nitrate in water has been studied using novel amperometric and optical sensors. A flow-injection analysis system with amperometric detection has been developed in which nitrate is determined as nitrite after reduction in a cadmium column. The working electrode is glassy carbon modified with a crosslinked redox polymer. The linear range is 0.1 to 190 mg/l NO3-N (r>>0.999) and the limit of detection (LOD) is 50 µg/l NO3-N. A fiber optic sensor based on a dual wavelength absorption approach has also been developed. A signal at 210 nm where nitrate absorbs was referenced against a signal at 275 nm where nitrate does not absorb. Its linear range is from 0.4 to 30 mg/l NO3-N and its LOD is 400 µg/l NO3-N. These diverse methods have been applied to the analysis of the same river water samples and good correlations have been observed between the two measurement techniques and a standard ion chromatography method.
Nitrate Amperometry Sensor Method comparison

"Clean Analytical Method For The Determination Of Propoxur"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 462-468
Miguel de La Guardia*, Karim D. Khalaf, Vicente Carbonell and Angel Morales-Rubio

Abstract: An FIA method for the determination of propoxur (I) was developed based on the alkaline hydrolysis of I to produce 2-isopropoxyphenol which was subsequently treated with p-aminophenol (PAP) in the presence of KIO4 to yield an indophenol dye. A 100 µL portion of an alkaline solution of I was injected into a 0.33 M NaOH carrier stream. The carrier stream was merged with a stream formed by merging 9.3 mM PAP with 0.2 M KIO4. After passing through a reaction coil the absorbance of the flow was measured at 600 nm using a 50 µL flow cell (path length 1 cm). All flow rates were 2.2 ml/min. The waste flow from the detector was irradiated at 254 nm in the presence of TiO2 to degrade excess PAP and the reaction products and so avoid environmental pollution with these substances. The calibration graph was linear for up to 100 µg/ml of I with a detection limit of 0.12 µg/ml. The RSD (n = 3) for the determination of 5 µg/ml I was 0.8%. For the determination of low levels of I (1 µg/ml) a pre-concentration step was introduced into the sample preparation procedure involving the extraction of I into CHCl3 and back-extraction into 0.33 M NaOH. Recoveries of 0.4-10 µg/ml I from tap, well and river water were 99%.
Propoxur Spectrophotometry Preconcentration

"Online Pervaporation Separation Process For The Potentiometric Determination Of Fluoride In 'dirty' Samples"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 246-252
I. Papaefstathiou, M. T. Tena and M. D. Luque de Castro*

Abstract: The FIA method was based on the reaction of fluoride with hexamethyldisilazane (HMDSA) in acidic medium to form trimethylfluorisilane (TMFS). TMFS was evaporated, diffused through a hydrophobic membrane and adsorbed into a NaOH acceptor stream. Fluoride was detected using a fluoride ISE. Streams of the sample solution and 1.5% HMDSA in 2 M H2SO4 were merged to give a combined flow of 0.5 ml/min and passed through a reactor coil (300 cm length) at 90°C. A portion of the solution was injected into a 1 M H2SO4 carrier stream (1.3 ml/min) and transferred to the pervaporation cell which was maintained at 80°C. The volatile TMFS was collected in a 0.05 M NaOH acceptor stream (1.3 ml/min). The acceptor stream was merged with a stream (1.3 ml/min) containing 0.2 M acetic acid and 1 M KCl before passing to the ISE detector. The system was operated in the continuous- and stopped-flow modes. The linear dynamic ranges were 40-100 ng/l (RSD = 2.6%) in the continuous-flow mode and 5-20 mg/l (RSD = 3.58%) in the stopped-flow mode. The sampling frequencies were 8 samples/h for the continuous-flow mode and 6 samples/h for the stopped-flow mode. The method was used to determine fluoride in water, fertilizers and ceramic industry waste water. The recovery of 10 and 50 mg/l fluoride from tap and well water was >89% and the RSD (n = 3) was 3.45%.
Fluoride Potentiometry Electrode Pervaporation Stopped-flow Hydrophobic membrane

"Graphite-poly(tetrafluoriethylene) Electrodes As Electrochemical Detectors In Flowing Systems"
Anal. Chim. Acta 1995 Volume 314, Issue 1-2 Pages 13-22
C. Fernández, A. J. Reviejo and J. M. Pingarrón*

Abstract: Graphite/PTFE composite electrodes (details given) were used as indicator electrodes for the flow injection amperometric detection of the herbicides, thiram (I) and disulfiram (II) at a potential of +1 V vs. Ag/AgCl/3 M KCl in a carrier stream (1.9 ml/min) of 0.1 M phosphate buffer at pH 7.4 and with an injection volume of 250 µL. Calibration graphs were linear up to 40 µM-I and -II and the detection limits were 0.043 and 0.02 µM, respectively. RSD (n = 10) were 7.7 and 5.7%, respectively, for 0.1 µM of I and II. Recoveries of 40 µg/l of I from spiked tap and well water were >97%. The adsorptive pre-concentration of the herbicides from flowing streams (2.7 ml/min) was carried out at 0.0 V. At the end of the pre-concentration period the phosphate buffer stream was passed for 30 s prior to the determination of the suface-bound herbicide by applying a linear sweep anodic potential ramp up to +1.2 V. Calibration graphs were linear from 0.4-1 and 0.2-1 µM-I and -II, respectively. The continuous-flow injection separation of I and II was carried out by inserting a 30-40 µm VYDAC SC-201 column (3 cm x 0.2 mm i.d.) into the FIA system and using acetonitrile/0.1 M phosphate buffer at pH 7.4 (1:3) as mobile phase (1.9 ml/min).
Disulfiram Thiram Amperometry Electrode Preconcentration Column

"Paraquat Sensors Containing Membrane Components Of High Lipophilicities"
Anal. Chim. Acta 1997 Volume 338, Issue 1-2 Pages 89-96
Bahruddin Saad*, Marinah Mohd. Ariffin and Muhammad Idiris Saleh

Abstract: Membrane-type ISE for paraquat were prepared using PVC membranes containing octamethylcyclotetrasiloxane as the sensing substance, bis-(1-butylpentyl)decane-1,1-diyl diglutarate or tetra-n-undecyl-3,3',4,4'-benzophenone tetracarboxylate as the plasticizer and sodium tetrakis-[3,5-bis(trifluoromethyl)phenyl] borate or potassium tetrakis-(4-chlorophenyl)borate as additive. The optimum compositions for the membranes were 3.6% sensor substance, 63.5% plasticizer, 30% PVC and 3% additive. The ISE were fabricated by casting the PVC membranes onto Pt electrodes and the potentiometric response to paraquat was measured against a Ag/AgCl reference electrode. All the ISE exhibited a Nernstian response to paraquat with response times of ~20 s for paraquat concentration greater than 10 µM. The detection limit was 1 µM-paraquat. The ISE were used in a FIA system with Trizma buffer at pH 5.5 as the carrier stream (2.6 ml/min) and an injection volume of 50 µL. The mean recoveries of 10 µM-paraquat from well, river and lake waters were 96.3%, 94.7% and 93.9%, respectively. The sample throughput was 85/h.
Paraquat Potentiometry Electrode Electrode Sensor Buffer

"Flow Injection Spectrophotometric Determination Of Cyanide By The Phenolphthalein Method"
Talanta 1997 Volume 44, Issue 4 Pages 545-551
Amin T. Haj-Hussein*

Abstract: Aqueous sample (50 µL) was injected into a carrier stream of 1 mM NaOH which merged with premixed streams of 0.3 mM phenolphthalin and 0.2 M carbonate buffer of pH 10.3. The flow passed through a column (6 cm x 1.4 mm i.d.) packed with 80 mg CuS particles (0.8-1.2 mm) where phenolphthalein was produced, and then to a detector where the absorbance was measured at 552 nm. The optimal flow rate was 1.08 ml/min. The calibration graph was linear for 0.6-4.3 ppm cyanide and the RSD were ~1%. The detection limit was 0.1 ppm. Interferences were investigated. The method was applied to well water. Recoveries were 98.7-101.5%.
Cyanide Spectrophotometry Column Detection limit Interferences Solid phase reagent Optimization

"Spectrofluorimetric Determination Of Sulfate In Waters In Normal And Open - Closed Flow Injection Configurations"
Analyst 1991 Volume 116, Issue 3 Pages 305-307
Beatriz Fernandez-Band, Pilar Linares, M. D. Luque de Castro and Miguel Valcárcel

Abstract: A 4 mM biacetyl mono-oxime nicotinoylhydrazone solution (1.02 mL min-1) was merged with 10 mM Zr(IV) in 2.4 M HCl (0.67 mL min-1), and this mixture was merged with sample in carrier solution (0.67 mL min-1) comprising 0.2 M NaOH or water for normal and open-closed systems, respectively. Fluorimetric detection was at 505 nm (excitation at 420 nm). In the open-closed system, the sample plug could be recirculated through the flow cell as required. For the normal system, the calibration graph was rectilinear for 2 to 30 and 30 to 150 µg mL-1, the coefficient of variation (n = 3) was 3.5% for 10 µg mL-1, and the sampling rate was 30 h-. Corresponding figures for the open-closed system were 1.5 to 150 µg mL-1, 2.3% and 6 or 12 h-1. Phosphate, MoO42-, F- and Fe(III) interfered in equimolar concentration. The method was applied to well, tap and bottled waters.
Sulfate Fluorescence Interferences Closed loop

"Catalytic Determination Of Dissolved Inorganic Carbon In Natural Waters By Flow Injection Spectrophotometry"
Analyst 1996 Volume 121, Issue 11 Pages 1617-1619
Nelson Maniasso, Sandra Sato, Maria F. Giné and Antonio O. Jacintho

Abstract: Sample was aspirated (2 ml/min) so as to fill a 750 µL sampling loop. The loop contents were injected into a carrier stream (1.6 ml/min) of 30 mg/l silicate of a flow injection manifold (schematic shown). The sample zone was merged successively, with reagent streams of 0.5 M acetate buffer of pH 5 (0.4 ml/min), Cr(III) (3 g/l aged for 10 days before use; 0.4 ml/min) and 0.3 M EDTA (0.4 ml/min). The mixture was passed through a 200 cm coil maintained at 45°C and the absorbance was measured at 540 nm. The calibration graph was linear for 10^-300 mg/l dissolved inorganic carbon (as hydrogencarbonate). The RSD (n = 9) at the 50 mg/l level was The throughput was 36 samples/h. The method was applied to lake, river, well and tap water. The results obtained agreed with those obtained by titrimetry.
Carbon, inorganic Spectrophotometry Buffer Method comparison Heated reaction Catalysis

"Flow Injection Determination Of Anionic Surfactants With Cationic Dyes In Water Bodies Of Central India"
Analyst 1998 Volume 123, Issue 8 Pages 1691-1695
Rajmani Patel and Khageshwar Singh Patel

Abstract: A new, simple and specific flow injection analysis (FIA) procedure for the determination of anionic surfactants, viz., sodium lauryl sulfate (SLS), sodium dodecyl sulfonate, sodium hexadecyl sulfonate and sodium dodecyl benzenesulfonate, with cationic dyes, viz., Brilliant Green, Malachite Green, Methylene Blue, Ethyl violet and Crystal Violet, in water bodies, viz., ponds, tube wells, rivers and municipal wastes, of central India (east Madhya Pradesh) is described. It is based on the precipitation of the cationic dyes with the anionic surfactant due to formation of an ion-associated species within the pH range 5.5-8.0. The apparent molar absorptivity of the ion-associated species formed with various anionic surfactants and cationic dyes is in the range (0.60-1.50) x 104 L mol-1 cm-1 at λmax 590-665 nm. Among them, the pair BG+-LS- was selected for detailed investigation. The detection limit (amt. causing absorbance >3s) of the method with BG is 100 ppb SLS and the sample throughput is 50 h-1. Optimization of FIA and the anal. variables in the precipitation and determination of SLS with BG is described. The method is free from interferences from almost all ions which are commonly present with the surfactant. The proposed method was applied to the mapping of SLS pollution levels in the various water bodies. All surface waters and municipal waste waters and some ground waters lying near the sources were found to be contaminated with SLS beyond permissible limits.
Surfactants, anionic Sodium lauryl sulfate Sodium dodecyl sulfonate Sodium hexadecyl sulfonate Sodium dodecylbenzenesulfonate Spectrophotometry Ion pair formation pH Optimization Interferences

"Determination Of N-methylcarbamate Pesticides In Well Water By Liquid Chromatography With Post-column Fluorescence Derivatization"
Anal. Chem. 1984 Volume 56, Issue 13 Pages 2465-2468
Kenneth M. Hill, Richard H. Hollowell, and Leo A. Dal Cortivo

Abstract: The compounds were separated by HPLC on a column (25 cm x 4.6 mm) of Zorbax C8 at 31°C with gradient elution with methanol - water. Derivatization was achieved on a Kratos URS 051 post-column reaction system, with phthalaldehyde and 2-mercaptoethanol, and fluorimetric detection was at >418 nm (excitation at 230 nm). Recoveries were generally >95% at pH <6.0 at the 8- and 40-ppb levels. In the analysis for aldicarb, good correlation between results by the method proposed and those of a g.c. method was obtained (r = 0.991). The HPLC method also allowed analysis for other pesticides, such as carbofuran and oxamyl.
Pesticides Aldicarb Carbofuran Oxamyl HPLC Fluorescence Post-column derivatization Heated reaction

"Determination Of Sulfate In Natural Water By Flow Injection Analysis"
Fresenius J. Anal. Chem. 1984 Volume 317, Issue 1 Pages 29-31
Susumu Nakashima, Masakazu Yagi, Michio Zenki, Mitsuo Doi and Kyoji T&ocirc;ei

Abstract: Dimethylsulfonazo III was used as reagent and the absorbance was measured at 662 nm. Interference by Ca was eliminated by inserting a column (8 to 15 cm) of Amberlite IR-120B resin (H+ form; 20 to 50 mesh) just after the sample-injection valve. To ensure good sensitivity and reproducibility, the carrier solution was saturated with BaSO4 and the reaction coil was filled with aqueous 50% ethanol when not in use. At a level of 10 mg L-1 of SO42-, the following (concentration. in mg l-1) did not interfere within 5% negative error: Mg and NH4+ (30); Na (50); K (80); and Cl-, NO3-, PO43-, HCO3- and SiO32- (100). The calibration graph was rectilinear up to 14 mg L-1 (K2SO4 standard). The coefficient of variation (n = 20) at 6 and 10 mg L-1 were 0.94 and 1.2%, respectively. In 9 separate samples of natural rain, tap, well and river waters, recoveries of added SO42- (4 and 6 mg l-1) ranged from 95 to 105%. A Shimadzu double-beam spectrophotometer with a 1-cm flow-through micro-cell (8 µL) was used, and the flow rates for both the reagent and carrier solution were 1.7 mL min-1. The sample solution (130 µL) was injected via a 6-way valve into the carrier stream. Flow lines were made of PTFE tubing (1 mm or 0.5 mm i.d.). The limit of detection was ~0.2 mg l-1. A flow diagram of the apparatus is given.
Sulfate Ion exchange Spectrophotometry Amberlite Interferences

"Selective Spectrofluorimetric Determination Of Zinc In Biological Samples By Flow Injection Analysis (FIA)"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 7 Pages 597-600
P. Fern&aacute;ndez, C. P&eacute;rez Conde, A. Guti&eacute;rrez and C. C&aacute;mara

Abstract: Sample (0.25 g) was heated at 500°C for 2 h in a muffle furnace. The residue was dissolved in 0.5 mL of HNO3 and the solution was diluted to 25 mL with water. A 125 µL portion of the resulting solution was injected into a carrier stream (0.62 mL minmin1) of 0.5 M hexamethylenetetramine adjusted to pH 6 with HClO4 which merged with a stream (0.36 mL min-1) of 0.05% of 5,7-dibromo-8-quinolinol in ethyl ether. The two phases were separated and the organic phase was passed through a flow cell where its fluorescence was measured at 550 nm (excitation at 410 nm). The calibration graph was rectilinear up to 1 µg mL-1 of Zn(II); the detection limit was 3 ng mL-1. Sample throughput was 40 h-1. Among the 30 cations and anions studied, only Ni(II), Mn(II) and EDTA interfered seriously. The method was used to determine Zn in tap and well water, muscle, milk powder and whole diet. The automatization of a spectrofluorimetric method for the determination of zinc at trace level is described. It is based on the formation of the fluorescent complex Zn(II)-5,7-dibromo-8-quinolinol [Zn(II)-DBQ] followed by extraction into diethyl ether using flow injection analysis The optimum fluorescent emission is reached in hexamethylenetetramine (H2MTA+/HMTA) buffer pH 6.0. A membrane phase separator was used. The calibration graph is linear up to 1.5 µg/mL of Zn(II). The proposed method (detection limit 3 ng/mL) is very selective and has been successfully applied to determine Zn(II) in biological samples, tap waters, and various food items.
Zinc Fluorescence Organic phase detection Optimization Interferences Reference material Phase separator

"Determination Of Trace Amounts Of Phosphate In Natural Water By Flow Injection Fluorimetry"
Anal. Lett. 1989 Volume 22, Issue 15 Pages 3081-3090
Wei, F.;Wu, Z.;Ten, E.

Abstract: Sample (50 µL) is injected into a carrier stream of water which then merges with merged streams fo 28 mM Mo(VI) - 0.8 M HCl and 20 µM-rhodamine 6G (C. I. Basic Red 1) - 0.025% of OP, and after passage through an 88-cm mixing coil the degree of fluorescence quenching at 550 nm is measured (excitation at 350 nm). The calibration graph is rectilinear for 100 ng mL-1 of P, and the detection limit is 2 ng mL-1. Only As(V) interferes, but can be masked by a 50-fold concentration. of S2O32-. Coefficients of variation (n = 12) for 10, 20 and 50 ng mL-1 of P were 5.4, 1.8 and 1.1%, respectively, and recoveries from tap-, well-, lake and pond water ranged from 92 to 102%.
Phosphate Fluorescence Quenching Interferences

"Integrated Retention - Spectrophotometric Detection Method For The Determination Of Formaldehyde"
Anal. Lett. 1992 Volume 25, Issue 12 Pages 2279-2288
Pablo Richter; M. D. Luque de Castro; Miguel Valc&aacute;rcel

Abstract: Sample solution (1 ml), containing 1 to 30 µg mL-1 of formaldehyde (I) was injected into a stream (0.5 mL min-1) of water. The stream was merged with 0.08% p-rosaniline - 0.4 M HCl - 0.1% Na2SO3 (1 mL min-1) and passed through a reaction coil (3 m x 0.5 mm). The reaction product was retained in a flow-through cell (40 µL, 1 mm path length) packed to a depth of 8 mm with Dowex 1-X-8 (Cl- form, 100 to 200 mesh). The retention signal was monitored at 560 nm and once it reached a max., the concentrated product was eluted with 2 M HCl saturated with 1-butanol. The coefficient of variation for 2 and 20 µg mL-1 of I were 2.8% and 1.35% respectively (n = 11) and the detection limits were 0.3 µg mL-1 of I for a 1 mL sample. Sampling frequency was 18 h-1; the detection limit was decreased to 75 ng mL-1 of I using a 2 mL sample, but the sampling rate then dropped to 10 h-1. Other aldehydes interfered less in this method than in conventional or stopped-flow injection analysis. An integrated-sensor method for the determination of HCHO in water was based on retention of the reaction product of the analyte with p-rosaniline and sulfite in a flow-cell packed with Dowex 1-X-8 anion exchange resin. The method has a good selectivity with a detection limit of 0.3 µg/mL (1 mL sample) or 75 ng/mL (2 mL sample), and a linear range 1-30 µg/mL. The relative standard deviations (n = 11) were 2.8 and 1.3% for 2 and 20 µg/mL HCHO, respectively. Depending on the working conditions, the sampling frequency ranged between 10 and 18 h-1. The method was applied to the determination of HCHO in well water.
Formaldehyde Spectrophotometry Dowex Interferences Selectivity Stopped-flow

"Ultraviolet Determination Of Chloride In Water By Flow Injection Analysis"
Anal. Lett. 1996 Volume 29, Issue 5 Pages 793-806
Amin T. Haj-Hussein

Abstract: Water (50 µL) was aspirated into the sample loop via a syringe and injected into 0.01 M EDTA in acetate buffer of pH 4.6 as carrier stream (0.74 ml/min). The sample was merged with 1 mM Hg-EDTA reagent (0.74 ml/min) also buffered at pH 4.6 and passed through a 25 cm reaction coil. Detection was at 250 nm. The calibration graph was linear from 1.8-35.5 ppm chloride with a detection limit of 0.2 ppm. The sampling rate was 60 samples/h. The method was applied to tap, well, spring and river water. Recoveries ranged from 97.5-101.2%.
Chloride Spectrophotometry

"High-sensitivity High Performance Liquid Chromatographic Analysis Of Diquat And Paraquat With Confirmation"
J. Chromatogr. A 1989 Volume 479, Issue 1 Pages 153-158
Verne A. Simon and Anne Taylor

Abstract: Paraquat (I) and diquat (II) were extracted from well water (containing 1,1'-diethyl-4,4'-bipyridinium di-iodide as internal standard) on a silica cartridge and eluted with aqueous 1.2% tetramethylammonium hydroxide pentahydrate (III) - 3% (NH4)2SO4 of pH 2.2 (adjusted with 50% H2SO4). HPLC was performed on two silica cartridges (each 3.3 cm x 4.6 mm) in series with aqueous 1% III - 3% (NH4)2SO4 of pH 2.2 as mobile phase (0.8 mL min-1). Detection was at 255 nm for I and 310 nm for II, or at 379 nm for both compounds after post-column derivatization with Na2S2O4. Calibration graphs for I and II after reaction with Na2S2O4 were rectilinear in the range 0.1 to 10 µg kg-1 (injection volume 50 µL).
Paraquat Diquat HPLC Spectrophotometry Sample preparation Extraction Post-column derivatization

"Spectrophotometric Determination Of Silicic Acid By Flow Injection Analysis"
Bull. Chem. Soc. Jpn. 1982 Volume 55, Issue 11 Pages 3477-3481
Takushi Yokoyama,Yukio Hirai,Norimasa Yoza,Toshikazu Tarutani and Shigeru Ohashi

Abstract: Flow injection analysis (FIA) was developed for the spectrophotometric determination of silicic acid based on the formation of a yellow molybdosilicic acid (yellow method) and a heteropoly blue complex (blue method). In the yellow method, silicic acid in the concentration range of 2 to 100 ppm (SiO2) could be determined at a sampling rate of 60 samples/h. The FIA system was modified to determine silicic acid in the presence of orthophosphate. Oxalic acid was used for the decomposition of molybdophosphoric acid. The modified system was employed for the rapid and selective determination of silicic acid in well and river waters. In the blue method, ascorbic acid was used to reduce the yellow molybdosilicic acid to a heteropoly blue complex. Silicic acid in the concentration range of 0.02 to 1.0 ppm (SiO2) could be determined at a sampling rate of 40 samples/h. The FIA system was also modified to determine silicic acid in the presence of orthophosphate. The reducing agent was introduced after molybdophosphoric acid had been completely decomposed by adding oxalic acid. The modified system was employed for the determination of silicic acid in sea water.
Silicic acid Spectrophotometry Interferences Heated reaction

"Flow Injection Analysis Of Phosphates In Environmental Waters"
Bunseki Kagaku 1981 Volume 30, Issue 7 Pages 465-469
Yukio HIRAI, Norimasa YOZA, Shigeru OHASHI

Abstract: High-pressure flow injection system developed for the determination of ortho- and polyphosphates was applied to the rapid analysis of phosphates in various environmental waters. A strongly acidic molybdenum (V) and molybdenum(VI) reagent was used so that hydrolysis of polyphosphates and color development of the resultant orthophosphate could be achieved simultaneously. A sample solution (0.5 ml) was introduced into a carrier stream of water via a loopvalve sample injector. The carrier stream meets a molybdenum reagent stream from another channel and flows together into a reaction tubing. For complete chemical reaction, the temperature of the reaction tubing (PTFE, 0.5 mm i.d., 1.5 mm o.d., 30 m) was maintained at 140°C. Residence time of the sample in the reaction tubing was about 4 min. The absorbance of heteropoly blue complex was monitored. at 830 nm. Sampling rate was 30 samples/h. Detection limit was 3 x 10^-7 M (0.010 ppm P). The precisions (C.V.) were 4.0 %, 0.3 % and 0.2 % for orthophosphate of 1 x 10^-6 M, 1 x 10^-5 M and 1 x 10^-4 M, respectively. It was found that the flow injection system was effective in determining phosphate in river and well water, but the concentrations of phosphate in sea water and tap water were too low to be monitored by the present system.
Phosphate Polyphosphates Spectrophotometry Heated reaction

"Determination Of Ultratrace Amounts Of Selenium(IV) In Water And Soil Extracts By Flow Injection Online Ion-exchange Preconcentration Hydride Generation Atomic Absorption Spectrometry"
Kexue Tongbao 1990 Volume 35, Issue 6 Pages 526-527
XU SHU-KUN, ZHANG SU-CHUN, FANG ZHAO-LUN

Abstract: Sample solution (9 mL min-1) was merged with 0.2 M acetate buffer (pH 5; 0.5 mL min-1) before passing through a column (4.5 cm x 3 mm) of D201 macroporous anion exchanger (50 mesh). Selenium was eluted with 1 M HCl (6 mL min-1) and the eluate was mixed with 0.5% of NaBH4 in 0.1% NaOH solution (2 mL min-1). The SeH4 was separated in a gas - liquid separator and carried by Ar (150 mL min-1) to a silica atomizer heated at 700°C for determination by AAS at 196.0 nm. The detection limit was 2 ng l-1, and the sampling rate was 50 h-1. The coefficient of variation were 1.1% (n = 11) for 0.5 µg L-1 and 6.4% (n = 10) for 0.01 µg l-1. Recoveries from tap, well and mineral waters were 96 to 100% and from soil extracts were 92 to 102%.
Selenium(IV) Ion exchange Spectrophotometry Clinical analysis Sample preparation Preconcentration Buffer pH Phase separator Detection limit Ultratrace Volatile generation

"Determination Of Trace PAHs In Water Samples By Synchronous Fluorophotometry With Flow Injection And Column Preconcentration"
Fenxi Ceshi Xuebao 1998 Volume 17, Issue 2 Pages 68-70
Lin Yuhui, Zhang Yong, Yuan Dongxing

Abstract: A simple and rapid synchronous fluorophotometric method couples with flow injection and column pre-concentration is described for the online simultaneous determination of trace benzo[a]pyrene (BaP) and perylene (Per) in tap and well water. The detection limits of BaP and Per are 0.2 µg.L-1 and 0.04 µg.L-1, respectively. The relative standard deviations are 7.10% and 7.54%, respectively. The recoveries are 93.3-103.3% and 103.3-116.7%, respectively.
Hydrocarbons, aromatic, polycyclic Benzo(a)pyrene Perylene Fluorescence Column Preconcentration

"Determination Of Fluoride In Water By Flow Injection Potentiometry With The Ion-selective Electrode"
Fenxi Huaxue 1987 Volume 15, Issue 9 Pages 825-827
Cui, H.;Fang, Z.L.

Abstract: A filtered sample of well- or surface water was mixed with a total-ionic-strength-adjustment buffer composed of NaCl, Na acetate, Na citrate and 36% acetic acid. The F- content of this mixture, calibrated against standard solution of F-, was determined by flow injection potentiometry with an ion-selective electrode that incorporated an AlF3 single-crystal slice. Optimum conditions were established with use of 200 ppb of F- in the carrier liquid to increase the stability and speed of response, reduce the signal noise of the potentiometer, and avoid interference by OH-. The detection limit was 0.02 ppm, the standard deviation (n = 11) for 0.5 ppm of F- was ±0.1 mV, and a sampling rate of 80 h-1 was achieved.
Fluoride Electrode Potentiometry Interferences

"Flow Injection Analysis Micellar-solubilization Spectrophotometry. 1. Determination Of Phosphorus At Microgram/liter Levels With The Ethyl Violet-heteropoly Acid-Triton X-100 System"
Fenxi Huaxue 1987 Volume 15, Issue 11 Pages 1022-1024
Yuan, Y.;Qu, K.

Abstract: The flow of the three reagent solution, viz, (A) 0.06 M in H2SO4 and 3 mM in MoO42-, (B) prepared by mixing 20 mL of 10% Na2S2O3 solution, 60 mL of 10% Na2SO3 solution (to eliminate interference of As(V)), 6 mL of 5% Triton X-100 solution and water to produce 200 ml, and (C) aqueous 0.12 mM ethyl violet (C. I. Basic Violet 4), is controlled by a peristaltic pump at 1.43 mL min-1, 0.67 mL min-1 and 1.41 mL min-1, respectively. solution A and B are mixed just before the injection of 1 mL of the sample or standard P solution (e.g., 42 µg l-1). solution C enters the system after passage of the sample solution through a coiled reaction tube (90 cm x 0.3 mm) and flow continues through another coiled reaction tube (300 cm x 0.8 mm) to an 8 µL detector cell for absorbance measurement at 553 nm. The calibration graph is rectilinear for up to 100 µg L-1 of P. The detection limit is 0.5 µg l-1. The method has been successfully applied to the determination of trace P in tap and well water.
Phosphorus Spectrophotometry Micelle Interferences Triton X Surfactant

"Stop-flow Reverse Flow Injection Analysis For Trace Manganese The Manganese(II)-sodium Phosphinate (NaH2PO2)-potassium Periodate NTA System"
Fenxi Huaxue 1988 Volume 16, Issue 4 Pages 315-319
Yuan, Y.;Wang, Y.;Qu, K.

Abstract: The water sample (tap water after removal of Cl by boiling, or polluted or well water after removal of bacteria by filtration) was merged with separate reagents of 1.1 mM KIO4 (40 µL) and 16% hexamine - HCl - NaOH buffer (pH 6.6), containing 0.15 mM NaH2PO2 and 0.3 mM nitrilotriacetic acid, in the stopped-flow apparatus (diagram given), and reacted in a 70-cm tube for 5 min followed by elution and absorbance measurement of Mn(II) at 236 nm. Both sample matrix and the hexamine reagent act as carriers. A rectilinear calibration graph is obtained for up to 5 µg L-1 of Mn(II) and the detection limit is 0.05 µg l-1. For determination of 3 µg L-1 of Mn(II), the coefficient of variation is 3% (n = 10). Most foreign ions, e.g., Al(III), Ba(II) (2 µg mL-1), Cr(VI) (6) and Pb(II) (1.6) do not interfere but Co(II) (>4 ng mL-1) produces a negative interference.
Manganese Spectrophotometry Interferences Reverse Stopped-flow

"Flow Injection Analysis Micellar-solubilization Spectrophotometry. 2. Simultaneous Spectrophotometric Determination Of Calcium And Magnesium With Xylenol Orange-cetyltrimethylammonium Bromide System"
Fenxi Huaxue 1988 Volume 16, Issue 6 Pages 546-548
Yuan, Y.;Wang, Y.;Qu, K.

Abstract: Flow injection analysis was used for the simultaneous spectrophotometric determination of Ca and Mg as complexes with xylenol orange in the presence of hexadecyltrimethylammonium bromide. Calcium and Mg were determined at 585 nm in a medium of NH3 - NH4Cl buffer (pH 10.5) containing triethanolamine, and then Ca was determined at 605 nm in NH3 - NH4Cl - Na citrate buffer containing triethanolamine. The calibration graph was rectilinear for Ca and Mg in the former buffer for up to 8 µg mL-1, and for Ca in the latter buffer, for up to 5 µg mL-1. The coefficient of variation was 1.4% for 4 µg mL-1 of Ca. The method was applied to the determination of Ca and Mg in tap water, well water and seawater. Results agreed well with those obtained by AAS.
Calcium Magnesium Spectrophotometry Complexation Merging zones Method comparison Simultaneous analysis Micelle

"Application Of A Photochemical Reaction In A Flow Injection System. 5. Determination Of Trace Amounts Of Nitrite With A Nitrate/luminol Photochemical Reaction System"
Fenxi Huaxue 1995 Volume 23, Issue 3 Pages 321-324
Liu, D.J.;Liu, R.M.;Sun, A.L.;Liu, G.H.

Abstract: Sample was adjusted to pH 5 and injected into a carrier stream of H2SO4 (1.5 ml/min) to mix in a photochemical reactor (180 cm) while irradiated with a high-pressure Hg lamp. It was then carried via a connection tube (11 cm) to react with a stream of 50 µM-luminol containing 0.1 M KOH of pH 13 (0.5 ml/min) in a reactor (3 cm) and the chemiluminescence intensity was measured. The calibration graph was linear for 50 nM- to 0.1 mM nitrate and the RSD were 0.74-0.92%. Fe(III), Cu(II), Co(II) and Ni(II) interfered seriously. The method was applied to river and well water and the results were compared with those obtained by the phenol disulfonic acid method.
Nitrate Chemiluminescence Photochemistry Interferences Method comparison

"Catalytic Spectrophotometric Determination Of Trace Manganese(II) By Flow Injection Analysis"
Fenxi Shiyanshi 1993 Volume 12, Issue 5 Pages 53-54
Zhu, H.Y.;Peng, A.S.;Zhang, L.

Abstract: Sample (50 µL) was injected and carried (all streams at 1.5 ml/min) by 6 M H3PO4, mixed with 0.01% diantipyrinephenylenemethane in a tube (40 cm x 0.5 mm) then with 2 mM Cr(VI) in a reaction tube (100 cm x 0.5 mm) at 40°C before detection at 540 nm. Relationship between peak height and concentration. was linear for 0.03-5 ng/ml of Mn2+. Most foreign ions did not interfere. The method was applied to analysis of hair and well water with recoveries of 93-110% and RSD of 2.9-6.4%.
Manganese(II) Spectrophotometry Catalysis Interferences

"Determination Of Nitrite In Water By Catalytic-kinetic Flow Injection Fluorimetry"
Fenxi Shiyanshi 1997 Volume 16, Issue 1 Pages 26-28
Wang, K.T.;Chen, X.G.;Hu, Z.

Abstract: Sample (120 µL) was injected into a carrier stream of water (0.8 ml/min) that merged first with a stream of 2.5 mM rhodamine 6G in 0.5 M H2SO4 (0.8 ml/min) in a mixing coil (12 cm x 0.5 mm i.d.) and then with a stream of 1.2 mM KBrO3 (1.2 ml/min) in a reactor (100 cm x 0.5 mm i.d.) before fluorimetric detection at 549 nm (excitation at 519 nm). The calibration graph was linear for 9-100 µg/l of nitrite, with a detection limit of 3.5 µg/l. Large quantities of chloride were removed by precipitation with Ag(I). The method was applied to the analysis of river water, well water and waste water, with recoveries of 94-108% and RSD of 0.81-1%. The sampling frequency was 65 runs per h.
Nitrite Fluorescence Catalysis Interferences Precipitation Kinetic

"Flow Injection Chemiluminescence Analysis And Its Application"
Huaxue Tongbao 1992 Volume 18, Issue 4 Pages 42-46
Li, G.H.;Yu, Z.N.

Abstract: A flow system was developed, based on the lumninol - CN- - Cu(II) system, and applied to the determination of Cu(II) in well, rain and lake water. Sample was filtered through a 0.454 µm filter paper and the filtrate was diluted with 10 mM Na4P2O7. The solution was injected into a flow coil in which a solution containing 0.033 mM luminol, 13.36 µg mL-1 of CN- and 0.033 M NaOH had merged with 0.1 M NaOH, and the chemiluminescence was measured. The calibration graph was rectilinear from 0.4 ng mL-1 to 0.8 µg mL-1 of Cu(II). The detection limit was 10 pg mL-1 of Cu(II). Recoveries were quantitative. The method was also applied to the determination of Co and Cr in natural water, Pb in waste water and H2O2 in tap water.
Cobalt Chromium Copper Chemiluminescence

"Studies On Precision For Silicate Determination By Flow Injection Analysis And Correlation Between The Flow Injection Method And Conventional Method"
J. Flow Injection Anal. 1989 Volume 6, Issue 2 Pages 151-159
Toshihiko Miyaji, and Kiyokatsu Kibi

Abstract: Two flow injection analysis methods are described. For method (i), sample (100 µL) is injected into a carrier stream (1 mL min-1) of water and mixed with a reagent stream (1 mL min-1) of 1% (NH4)2MoO4 in 0.25 M HCl at 60°C in a 3-m coil followed by a stream of 2% oxalic acid (0.5 mL min-1) and detection at 400 nm. For method (ii), an additional reagent stream containing 0.05% 1-amino-2-naphthol-4-sulfonic acid, 0.2% Na2SO4 and 2% NaHSO3 (0.5 mL min-1) was added to the mixture used in method (i) just before detection at 815 nm. After addition of 2% oxalic acid, P and As at 50 ppm, 1 ppm of Fe(III) and 2% of NaCl did not interfere. Detection limits for (i) and (ii) were 0.03 and 0.0023 mg L-1 of Si, respectively; for the determination of 10 ppm of Si by method (i) and 1 ppm of Si by method (ii), the corresponding coefficient of variation (n = 10) were 0.45 and 0.59%. Sample throughput was 60 h-1. Results obtained by methods (i) and (ii) correlated well with each other and the Japanese Industrial Standard method. The methods were applied in the analysis of tap water, well water and industrial waste water.
Silicate Spectrophotometry Precision Method comparison Standard method Interferences

"Determination Of Iron In Water By Flow Injection Analysis"
Lihua Jianyan, Huaxue Fence 1988 Volume 24, Issue 2 Pages 89-90
Yu, Z.;Zhang, N.

Abstract: A 100 µL water sample (industrial or well water) is fed into a flow injection analysis system (flow diagram given) in which Fe is allowed to react with 0.05% 1,10-phenanthroline - 0.2% hydroxylammonium chloride - Na acetate mixed chromogenic solution to form a red chelate in Na acetate - HCl buffer solution (pH 5), and the change in absorbance is measured by using a Model 721 spectrophotometer. The calibration graph is rectilinear up to 4 ppm of Fe. Recovery is 98 to 102% with a coefficient of variation of 1.2%. The detection limit is 0.02 ppm. Most co-existing ions do not interfere. Results compared well with those by manual photometry.
Iron Spectrophotometry Chelation Interferences Method comparison