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 -> water -> estuarine

Citations 21

"A Flow Injection-fluorometric Method For The Determination Of Ammonium In Fresh And Saline Waters With A View To In Situ Analyses"
Water Res. 2001 Volume 35, Issue 7 Pages 1777-1785
Alain Aminot, Roger Kérouel and Dominique Birot

Abstract: A version of the orthophthaldialdehyde-fluorescence ammonium determination for flow injection analysis (FIA) is presented here, with a view to its use for in situ, low-power consumption systems, Thus, the reaction temperature was limited to 30°C and FIA was used in stop-Bow mode (3 min stop). The calibration is linear up to 50 µmol L-1, but concentrations up to 100 µmol L-1 can be measured. Repeatability is around 1% in the range of 0.5-4 µmol L-1 and the detection limit is about 0.03 µmol L-1 Over the salinity range of 5-35 (seawater practical salinity scale) the salt effect is almost negligible (within±2%); and below salinity of 5 it increases to a maximum of -9% in fresh water compared to seawater. Hydrogen carbonate, dissolved oxygen and turbidity (either suspended sediments or phytoplankton cells) have almost no adverse effect in a wide range of concentrations, covering most natural water conditions. Relative interference of primary amines is negligible and mercury (a common sample preservative) does not depress the signal up to 20 mg L-1 Hg II. Sulfide, that may be present in areas with anoxic waters, depresses the signal only slightly and linearly (-9% at 100 µmol L-1 S2-). The method appears to be convenient for the determination of ammonium in most coastal, estuarine and fresh waters. Sample throughput is 9 h-1. The performance of the method can be improved, either by increasing the reaction time (low throughput) or, if enough energy is available, by increasing the reaction temperature (non-stop-flow mode, high throughput). Combining FIA and fluorometry appears to be interesting for in situ determination (submersible devices) of dissolved compounds in environments with variable salinity and turbidity (especially coastal and estuarine waters). (C) 2001 Elsevier Science Ltd. All rights reserved.
Ammonium Fluorescence Interferences Optimization Method comparison Reagent stability Remote instrument

"Determination Of Arsenic Species In Seawater By Flow Injection Hydride Generation In Situ Collection Followed By Graphite Furnace Atomic Absorption Spectrometry - Stability Of As(III)"
Anal. Chim. Acta 2000 Volume 418, Issue 1 Pages 19-31
Jean Yves Cabon and Nolwenn Cabon

Abstract: Dissolved arsenic is present in seawater at the 1 µg L-1 level in various chemical forms: mainly, As(III) and As(V) inorganic arsenic, MMA, DMA, and eventually, unknown organic compounds. The concentrations of the minor arsenic species are well below the detection limit of graphite furnace atomic absorption spectrometry (GFAAS). Therefore, a pre-concentration/separation step is generally required before their determination. In this study, arsenic species were determined in seawater by flow injection hydride generation (FI-HG), collection within the graphite furnace, followed by atomic absorption spectrometry. This protocol permitted a pre-concentration factor of about 1000 lowering the detection limit of arsenic in seawater to about 1.5 ng L-1 for a 10 mi sample volume under optimized experimental conditions. Based on the different responses of arsenic species towards hydride generation, an experimental protocol for arsenic speciation was proposed. Total arsenic could be determined after a thermal or a UV irradiation treatment in an alkaline persulfate medium after the conversion of all arsenic species to inorganic As(V). Total hydride-reactive species (As(III), As(V), monomethylarsenic (MMA) and dimethylarsenic (DMA)) could be determined for high NaBH4 and HCl concentrations because a similar analytical response was obtained for these individual species. As(III) could be determined alone by performing hydride generation in seawater at a pH of about 7-8. Non-hydride-reactive arsenic species were determined by the difference between total arsenic and hydride-reactive species. According to this analytical protocol, arsenic species were determined in reference estuarine and coastal seawaters. Hydride-reactive arsenic species were the major compounds, probably mainly As(V); this study tended also to confirm the presence of non-hydride-reactive organic species in seawater (15%). We also showed that As(III) was not stable in acidified seawater and was also slowly converted to As(V) in a coastal surface seawater at its natural pH. These results indicated that time and preservation conditions could severely modify the speciation of arsenic in seawater, particularly for the preservation of As(III).
Arsenic(3+) Arsenic(5+) Dimethylarsenic Monomethylarsine Spectrophotometry Speciation Preconcentration Reference material Optimization

"A Novel Flow-through Disk-based Solid-phase Extraction Diffuse Reflectance Optrode. Application To Preconcentration And Determination Of Trace Levels Of Nitrite"
Analyst 2001 Volume 126, Issue 10 Pages 1740-1746
Manuel Miró, Wolfgang Frenzel, José Manuel Estela and Víctor Cerdà

Abstract: A novel, versatile and sensitive flow-through optical fiber diffuse reflectance sensor to implement disk-based solid-phase extraction in a flow injection analysis (FIA) system is presented. Nitrite optosensing at trace levels is chosen as a model of chemistry to demonstrate its applicability. The methodology is based on on-line nitrite derivatization with Shinn reagent to form a moderately polar azo dye, whose pre-concentration oil to octadecyl covalently bonded silica gel particles tightly bound to an inert matrix (C-18 disk) is continuously monitored using a plug-in diode-array spectrophotometer. After the analytical signal has been recorded, fast sensor regeneration is achieved with a methanolic eluent, rendering the system ready for the next extraction. Selection of the solid disk support and the suitable flow-through cell configuration to reduce back-pressure effects are discussed in detail. By matching the illumination and retention zones, concentrations of nitrite as low as 1 ng mL-1 are easily determined using 2.5 mL of sample. A detection limit (3s (blank)) of 0.1 ng mL-1 of nitrite, repeatability and reproducibility better than 3.2%, an analytical throughput of 11 h-1 and an enrichment factor of 140 are the figures of merit of the proposed optrode. The utility of the flow-through optosensing system, wherein minimization of additive matrix interferences is feasible, was testified by the satisfactory results obtained in its application to tap, ground, harbor and aquarium water samples.
Nitro compounds Sensor Spectrophotometry Optrode C18 Preconcentration Optimization Interferences

"Determination Of Nickel, Cobalt, Copper And Uranium In Water By Cathodic Stripping Chronopotentiometry With Continuous-flow"
Anal. Chim. Acta 1987 Volume 199, Issue 1 Pages 59-76
M. P. Newton and C. M. G. Van Den Berg

Abstract: An automated analyzer. with fast data acquisition (250 kHz) is described. Adsorptive collection of surface-active metal complexes on a hanging-mercury-drop electrode is followed by cathodic scans in which a constant current of 0.8 to 60 µA is passed through the working electrode. Copper, U and Ni can be determined in the presence of dissolved O but the sensitivity for Ni is then much reduced, and Co cannot be determined as its peak is superimposed on the O peak. The sensitivity of stripping chronopotentiometry in the presence of dissolved O is similar to that of fast linear-sweep voltammetry in the absence of dissolved O. Detection limits in deaerated seawater are 0.1, 0.1, 1.8 and 1.6 nM for Ni, Co, Cu and U, respectively, using 60-s stirred adsorption and could be lowered further by prolonged collection (300 s). The technique was successfully applied in measuring Ni with continuous-flow in estuarine water.
Nickel Cobalt Copper Uranium Potentiometry Electrode Voltammetry Interferences

"Intelligent Flow Injection Inductively Coupled Plasma System For Matrix Matching"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 207-212
M. F. Giné, H. Bergamin, B. F. Reis and R. L. Tuon

Abstract: Estuarine waters of varying salinity were analyzed by a flow injection analysis system, with ICP-AES detection of Ca, Mg, Al, Fe, P and Si. The sampling zone approach was used to balance the salt content of samples and standards in order to compensate for matrix effects. This matching was achieved automatically by processing the sample Na signal with a microcomputer and adding Na+ as necessary. The matrix-matching procedure and the decision process are discussed. Interference by Na+ was thus minimized, allowing analysis of samples containing 2.5% of NaCl. The sampling rate was 60 h-1. Recoveries were >96%.
Calcium Magnesium Aluminum Iron Phosphorus Silicon Spectrophotometry Interferences

"Time-based And Volume-based Sampling For Flow Injection Online Sorbent-extraction Graphite-furnace Atomic Absorption Spectrometry"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 477-487
Bernhard Welz*, Xuefeng Yin and Michael Sperling

Abstract: Separation of the analyte from the sample matrix, and its pre-concentration, were achieved by use of a Perkin-Elmer model FIAS-200 flow injection accessory having its sample loop replaced by a conical micro-column (Eppendorf pipette tip) packed with 15 µL of RP-C18 solid-phase sorbent. The flow injection manifold was connected to the sample-introduction capillary of a Perkin-Elmer model Zeeman/3030 AAS instrument equipped with an HGA-600 graphite tube furnace and an AS-60 furnace autosampler. Details and diagrams are given of the sequence of operations for pre-concentration, involving volume-based sub-sampling; the system was more sensitive than one involving time-based sub-sampling. The system was applied in the determination of Cd, Cu, Pb and Ni. The acidified sample was mixed with a pre-purified 0.05% solution of Na diethyldithiocarbamate (I) in 0.06 M NH3 - 0.03 M acetic acid buffer (pH 9), and the metal - I complex was adsorbed on the micro-column. The column was then washed in the reverse direction with 0.02% (v/v) HNO3 before elution of the complex with ethanol and transfer of only 40 µL of the eluate to the graphite tube; furnace operating parameters are specified. With 60-s pre-concentration. of the analyte, the detection limits for Cd, Cu, Ni and Pb were 0.6, 8.5, 21 and 4 ng l-1, respectively. The method was used to determine the cited metals in standard reference seawater (open-ocean and coastal), estuarine water and river water; results agreed well with reference values. Flow injection online pre-concentration. systems for graphite furnace atomic absorption spectrometry are complicated by the low eluate volume of typically less than 50 µL which can be accommodated in a graphite tube or on a graphite platform. Even when a column with an extra small capacity of 15 µL was used, it was found impossible to elute the sorbed analyte completely with an eluate volume that was compatible with the capacity of the graphite furnace. Two approaches for introducing only the most concentrated fraction of the eluate into the graphite tube while discarding the rest were investigated and compared: controlling the time interval for collection and introduction of the eluate fraction into the furnace tube (time-based sampling), and collection of the eluate fraction of interest in thin tubing of fixed volume, followed by introduction of this fraction into the tube using a low flow of air (volume-based sampling). Cadmium, copper, lead and nickel were the analyte elements investigated. A 15-30% greater enhancement factor was obtained for volume-based sampling because dispersion was interrupted during sample injection by air segmentation. The short- and long-term reproducibility were also better for volume-based sampling because variations in the pump tubing had no influence on the eluate volume introduced. These combined effects resulted in an improvement in detection limits of the four elements by factors of 1.3-2.0. Sample throughput (23 h-1), sample consumption (3 mL min-1) and reagent consumption were the same for both approaches. There were no significant differences in the accuracy and precision of the two techniques in the anal. of seawater, estuarine water and river water standard reference materials.
Cadmium Copper Lead Nickel Spectrophotometry Sample preparation Matrix removal Preconcentration Timed injection Reference material FIAS-200 Reagent consumption Solid phase extraction

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

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

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

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

"Elimination Of The Schlieren Effect In The Determination Of Reactive Phosphorus In Estuarine Waters By Flow Injection Analysis"
Anal. Chim. Acta 1997 Volume 351, Issue 1-3 Pages 265-271
Ian D. McKelvie*, Darren M. W. Peat, G. Peter Matthews and Paul J. Worsfold

Abstract: Conventional flow injection manifolds with sample injection for the determination of reactive phosphorus in estuarine waters are limited by the Schlieren or refractive index (RI) effect which can cause major errors in quantification. A simple flow injection (FI) manifold which obviates this RI error in reactive phosphorus measurement is reported. It involves the injection of acidic molybdophosphate reagent into a carrier stream of sodium chloride solution of similar refractive index, which is then sequentially merged with a sample (the salinity of which may vary widely from sample to sample) and a reductant. Despite the occurrence of sizeable blank signals, reactive phosphorus has been successfully measured in samples with salinities ranging from 0 to 34 parts per thousand using calibration standards prepared in deionised water, with a detection limit of 6 µg L-1 P. 21 References
Phosphorus Refractive index Portable Optimization

"Direct Trace Determination Of Lead In Estuarine Water Using In-situ Preconcentration Of Lead Hydride On Ir, Zr And W-coated Graphite Tubes"
Anal. Chim. Acta 1998 Volume 368, Issue 3 Pages 281-289
Pilar Bermejo-Barrera*, Jorge Moreda-Pi&ntilde;eiro, Antonio Moreda-Pi&ntilde;eiro and Adela Bermejo-Barrera

Abstract: Methods for the direct trace determination of lead in sea water involving hydride generation, trapping and the atomization of the hydride generated in a graphite furnace has been developed. Different permanent coated graphite tubes: iridium, tungstate and zirconium coated graphite tubes were investigated for the in situ pre-concentration of lead hydride. The results obtained were compared with the ones achieved by the conventional HG-AAS. Trapping on Ir-coated graphite tubes offers the best analytical performances, with detection limits of 60 ng 1-1. The accuracy was studied using IAEA/W-4 and SLRS-2 reference materials, and the method was applied to several sea water samples. The number of samples analyzed in an hour was 40. 41 References.
Lead Spectrophotometry Volatile generation Reference material

"Determination Of Trace Amounts Of Zinc In Water Samples By Flow Injection Isotope-dilution Inductively Coupled Plasma Mass Spectrometry"
Analyst 1997 Volume 122, Issue 3 Pages 233-237
Tarn-Jiun Hwang and Shiuh-Jen Jiang

Abstract: A water sample (25 ml) was adjusted to pH 4 with 5 mL 1 M ammonium acetate buffer. After a suitable amount of Zn-67 had been added, the solution was diluted to 50 mL with water. A portion (10 ml) of the resulting solution was loaded at a flow rate of 10 ml/min on to a column (5 cm x 10 mm i.d.) of SO3-quinolin-8-ol carboxy-methylcellulose. The column was washed with 0.1 M ammonium acetate buffer of pH 4; the retained Zn was eluted (3 ml/min) with 0.5 M HNO3. The eluate was analyzed by ICP-MS (details given). The Zn-66/Zn-67 isotope ratio was calculated from the peak areas of the flow injection peaks. The calibration graph was linear up to 50 ng/ml Zn-66; the detection limit was 14 pg/ml. RSD was 1.4% (n=7). The method was applied to several water CRM; the results agreed with the certified values.
Zinc-66 Zinc-67 Mass spectrometry Mass spectrometry Column Detection limit Reference material Buffer

"Determination Of Dissolved Reactive Phosphorus In Estuarine Waters Using A Reversed Flow Injection Manifold"
Analyst 1997 Volume 122, Issue 12 Pages 1477-1480
Stefan Auflitsch, Darren M. W. Peat, Ian D. McKelvie and Paul J. Worsfold

Abstract: The Schlieren or refractive index (RI) effect is a major problem in the determination of dissolved reactive phosphorus in estuarine waters using conventional flow injection (FI) manifolds with sample injection, This is because differences in RI between the injected sample zone and the carrier stream give rise to a lensing effect which is superimposed on the blank response and causes significant error in quantitation, A simple reversed flow injection (rFI) manifold using spectrophotometric detection which removes these quantitation errors is reported. Acidic molybdate is injected into a sulfuric acid carrier stream of the same refractive index and sequentially merged with sample and reductant (ascorbic acid), Reduction of phosphomolybdate to phosphomolybdenum blue is carried out in a coil thermostated at 60°C. Dissolved reactive phosphorus has been successfully determined in estuarine waters with salinities ranging from 0 to 30 parts per thousand using calibration standards prepared in deionized water, with a detection limit of 2 µg L-1 PO4-P and a linear range of 2-100 µg L-1 PO4-P (r2 = 0.9998).
Phosphorus Spectrophotometry Reverse Refractive index Heated reaction

"Sensitive Determination Of Selenium By Inductively Coupled Plasma Mass Spectrometry With Flow Injection And Hydride Generation In The Presence Of Organic Solvents"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 10 Pages 865-870
Riansares Mu&ntilde;oz Olivas, C. R. Qu&eacute;tel and O. F. X. Donard

Abstract: Two sample introduction methods, viz., pneumatic nebulization and hydride generation via a flow injection system were used to study the optimum conditions for Se determination. The effect of organic solvents in polyatomic interferences (40Ar, 37Cl, 40Ar, 38Ar and 40Ar2H2) suppression and signal enhancement were investigated. The organic solvents studied were: methanol, ethanol, propanol, acetone and acetonitrile. A SCIEX Perkin Elmer 5000 spectrometer was used. The pneumatic nebulization flow rate ranged from 0.95-1.05 L/min and the Ar flow rate for hydride generation was similar (1.05-1.1 L/min); other operating conditions are tabulated. Under optimum conditions (NaBH4 = 0.2%, pH = 1, methanol load = 6%) for flow injection hydride-generation ICP-MS a detection limit of 1 pg of Se was obtained using a 200 µL sample. The average RSD was 2%. The method was applied to estuarine water and Se levels ranged from 5 to 70-80 ng/L. Validation was via an EC certification campaign.
Selenium Mass spectrometry Volatile generation Optimization Organic solvent Method comparison Interferences Signal enhancement Volatile generation

"Application Of Multielement Time-resolved Analysis To A Rapid Online Matrix Separation System For Inductively-coupled Plasma-mass Spectrometry"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 11 Pages 929-933
Simon M. Nelms, Gillian M. Greenway and Robert C. Hutton

Abstract: A rapid online matrix separation system for ICP-MS, using multi-element time-resolved analysis, was developed for the determination of several trace elements in complex matrix samples, A flow injection manifold was constructed consisting of a mini-column of 8-hydroxyquinoline covalently immobilized on to controlled pore glass, Analytes retained on the column were eluted using 0.1 mi of 2.0 mol L-1 nitric acid, Sample volumes of 0.5 mi were analyzed, yielding a pre-concentration factor of 5 in addition to matrix separation, The system was optimized with respect to the variables of buffer concentration, buffer pH and eluent acid volume and concentration, Calibrations from both pure water and synthetic seawater compared well and showed good linearity, with correlation coefficients of 0.988-0.999 for a range of analytes, The method showed good within-run reproducibility with precisions (s(r)) at the 1 ng mL-1 level of typically <3%, In general, recoveries between 89 and 104% were obtained, with the exception of Ni, which showed a recovery of 78% under the compromise conditions used. The method was validated by the analysis of estuarine (SLEW-1) and coastal (CASS-2) certified reference materials, Good agreement with the certified values was obtained for both of these materials. (17 references)
Metals, trace Mass spectrometry Sample preparation 8-Hydroxyquinoline Controlled pore glass Optimization Preconcentration Reference material Solid phase extraction

"Determination Of Copper, Cadmium, Manganese, And Lead In Saline Water With Flow Injection And Atom Trapping Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1998 Volume 13, Issue 7 Pages 631-634
Lyndon A. Ellis and David J. Roberts

Abstract: A flow injection device has been developed to sep. Cu, Cd, Mn and Pb from a solution of sodium chloride, thus minimizing interference and enabling their accurate determination in high salinity waters such as sea- or estuary water. Micro-columns of Chelex 100 resin were used and parameters of ammonium acetate buffer concentration, pH and the concentration. of a buffer flush have been optimized. Close to 100% recovery of the transition elements and 99.8% exclusion of sodium chloride was achieved. Atom trapping atomic absorption spectrometry (ATAAS) was used as the detection technique to determine concentrations. of the four elements at four sites on the Severn Estuary. In addition, a water cut-off device has been incorporated to improve the safety of the AT app.
Copper Cadmium Manganese Lead Spectrophotometry Interferences Chelex Buffer

"Selective Determination Of Inorganic And Total Mercury By Cold Vapor Atomic Fluorescence Spectrometry Coupled With Flow Injection Analysis"
Anal. Sci. 1990 Volume 6, Issue 1 Pages 91-95

Abstract: An aqueous sample (0.6 ml), containing 0.5 to 20 ppb of Hg(II), is injected into a stream of 0.5 M H2SO4. Organomercury compounds, e.g., methylmercury chloride, are irradiated in a flow system for 1.5 min in 0.05 M H2SO4 with a 400-W UV lamp before sample injection. The Hg(II) is reduced to elemental Hg with SnCl2 solution (1 to 10%) in 0.5 M H2SO4, and the Hg is separated by passage through PTFE tubing counter-current to a flow of Ar in an outer tube. Any water in the Ar is removed by condensation at -5°C and Hg is determined by AFS in a special cell with irradiation at 253.7 nm and measurement with a solar-blind photomultiplier. The limit of detection is 0.18 ppb of Hg is reported. Of the substances tested only cysteine interferes in the determination of total Hg probably via decomposition to S2-. The coefficient of variation were 2% (n = 10). The sampling rate was 20 h-1.
Mercury Methylmercury ion Fluorescence PPB Detection limit Interferences UV reactor Photochemistry

"Flow Injection Determination Of Nitrate In Estuarine And Coastal Waters"
Anal. Proc. 1994 Volume 31, Issue 3 Pages 81-83
Trevor McCormack, Anthony R. J. David, Paul J. Worsfold and Robin Howland

Abstract: Water (260 µL) was injected into a NaCl stream (0.23 ml/min), merged with an NH4Cl carrier stream (0.23 ml/min) and mixed thoroughly in a column (2 cm x 3 mm i.d.) packed with glass beads (1.5-2 mm o.d.). After mixing, the stream passed through a Cd reactor column and was merged with the color reagent stream (0.16 ml/min) composed of N-(1-naphthyl)ethylenediamine dihydrochloride/sulfanilamide in a reaction coil (200 cm). The resulting pink-purple color was detected spectrophotometrically at 540 nm. The FIA manifold is shown schematically. The calibration graph was linear from 0.1 (detection limit) to 73 µM-nitrate. For higher nitrate concentrations, as occur in terrestrial discharges, the range can be extended up to 730 µM-nitrate by the use of a 50 µL sample loop. The RSD (n = 6) were 1.6 and 2% for 73 and 1 µM-nitrate, respectively.
Nitrate Spectrophotometry Glass beads

"Determination Of Dissolved Vanadium In Natural Waters By Flow Injection Analysis With Colorimetric Detection"
Limnol. Oceanogr. 1998 Volume 43, Issue 3 Pages 526-529
Shiller, Alan M., Lunjin Mao, and Jeram&eacute; Cramer

Abstract: A flow injection technique for the determination of dissolved V in natural waters utilizes the V-catalyzed oxidation of Bindschedler's green leuco base by bromate with tiron and tartrate as reaction activators. The reaction product is quantified colorimetrically. A chelator column of immobilized 8-hydroxyquinoline reduces matrix effects but can be eliminated if samples with a constant matrix are being analyzed. Using the chelator column, 1 mL of sample can be analyzed in <10 min with a detection limit of 0.2 nM. The method was used for the determination of dissolved V in river and estuarine waters.
Vanadium Spectrophotometry Chelation 8-Hydroxyquinoline

"Monitoring Of Labile Copper And Zinc In Estuarine Waters Using Cathodic-stripping Chronopotentiometry"
Mar. Chem. 1991 Volume 34, Issue 3-4 Pages 211-223
C. M. G. van den Berg

Abstract: The sensitivity of cathodic-stripping chronopotentiometry was not affected by variations in salinity or by dissolved O, which rendered this technique suitable for the online automated determination of Cu and Zn in the Tamar estuary. The measurement rate was ~90 samples h-1 and the detection limits were 5 nM and 6 nM for Cu and Zn, respectively. The results agreed with the findings of previous studies. The online measurements eliminated the problem of sample contamination, provided a detailed picture of metal behavior in the estuary and elucidated local inputs. The technique is less sensitive than differential pulse cathodic-stripping voltammetry, but does not require sample filtration or deaeration, which facilitates its application to continuous-flow analysis. The sensitivity was not sufficient, however, to monitor Cu and Zn concentration. in uncontaminated seawater.
Copper Zinc Potentiometry Automation Method comparison Interferences Sensitivity

"Hydrogen Peroxide Determination In Estuarine And Marine Waters By Flow Injection With Fluorescence Detection"
Oceanol. Acta 1995 Volume 18, Issue 3 Pages 353-361
Amouroux D, Donard Ofx

Abstract: The Scopoletin-Peroxidase fluorescence decay method has been developed using standard additions and a flow injection manifold for hydrogen peroxide (H2O2) determination in marine waters. The limit of detection of the method was optimized using stored milli-Q water with a minimum of 5 nM (3s). The method was found to be linear from 5 to 700 nM, with an approximate relative standard deviation of 10%. This accuracy was verified on both milli-Q and natural waters running systematically duplicate analysis. (35 References)
Hydrogen peroxide Fluorescence Optimization Photochemistry Standard additions calibration

"Determination Of Indium In Natural Waters By Flow Injection Inductively Coupled Plasma Mass Spectrometry"
Proc. Indian Acad. Sci. 1998 Volume 107, Issue 4 Pages 359-366

Abstract: Two methods were developed to measure In in natural waters by flow injection inductively coupled plasma mass spectrometry (ICP-MS). One is the isotope dilution technique using an 113In enriched spike and the other utilizes natural Y present in the sample as an internal standard In the former, optimization of the 113In spike to minimize error is often difficult for samples in which In concentrations are variable, whereas in the latter method, a sep. determination of Y in the sample is necessary and hence more sample is required. Using ≈1 L of a water sample, 200-fold pre-concentration of In was performed by solvent extraction and back extraction technique and then introduced into the ICPMS to measure the 113In/115In or 115In/89Y ratios. The detection limits were 0.01-0.02 pmol kg-1 for both methods. Application of the methods to seawater samples yielded the concentrations of 0.06-0.15 for the Pacific and 0.6-1.5 pmol kg-1 for the Atlantic. The large inter-oceanic variation of In best resembles that of Al amongst the 3B group of elements in the periodic table. River and estuarine samples gave a more variable range of concentrations of 0.01-15 pmol kg-1. Most of the In supplied by rivers is removed by scavenging in the estuarine mixing zone, suggesting that the fluvial input of In to the ocean is small.
Indium Mass spectrometry Mass spectrometry Sample preparation Optimization Calibration