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 -> geothermal

Citations 7

"Automatic Determination Of Iron In Geothermal Fluids Containing High Dissolved Sulfur-compounds Using Flow Injection Electrothermal Atomic Absorption Spectrometry With An Online Microwave Radiation Precipitation-dissolution System"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 295-303
J. L. Burguera*, M. Burguera and C. E. Rondon

Abstract: A flow injection sample introduction in electrothermal atomic absorption spectrometry was used to determine iron in geothermal fluids containing high concentration. of dissolved sulfate and sulfide anions. First, sulfide was pptd. as sulfur with a confluencing solution of hydrogen peroxide (10% v/v) on the walls of a knotted reactor exposed to microwave radiation, to ease the precipitation process. While the sulfate containing solution flows downstream and sequestered in a sampling arm for the sequential deposition of aliquots of sample on the graphite tube atomizer platform bypositive air displacement, sulfur was dissolved with CCl4 and diverted to waste. This sequence was timed to synchronize with the spectrometer computer, which had been pre-programmed to introduce aliquots of Lu modifier, previous to each sample deposition, to minimize the sulfate interference, to improve integrated absorbance signal and the reproducibility of measurements. By using the less sensitive iron line at 296.7 nm, the linear range was 12-280 µg L-1, with a characteristic slope of 0.00083, a characteristic mass of 104.8 pg and a detection limit of 72 pg (3.6 µg L-1). The precision of the method, obtained for 10 measurements, was studied as within-run and within-batch precision; the relative standard deviations obtained in both cases were <3%. The accuracy of geothermal fluids was checked by recovery tests and comparison with an independent anal. method. Results obtained by the here proposed method correlate closely with those obtained by a tedious photometric procedure with o-phenanthroline. The sensitivity and the simplicity of this online procedure makes it attractive for routine determination of iron in waters involving large throughput of samples.
Iron Spectrophotometry Precipitation Knotted reactor Interferences Method comparison Microwave

"Online Ion Exchange For The Removal Of Sulfur Anion Interference On The Determination Of Manganese In Geothermal Fluids By Flow Injection Electrothermal Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 7 Pages 479-482
J. L. Burguera, M. Burguera, C. Rivas, P. Carrero, M. Gallignani and M. R. Brunetto

Abstract: Geothermal waters (1 l) were collected (details given) and mixed with 20 mL 1 M triethanolamine. The solution was injected into a flow system (schematic shown) with water as carrier (2.5 ml/min) and drawn through an online anion-exchange column packed with Dowex-1 X8 (NO3- form; mesh size 100-200). Manganese was eluted from the column with 2 mM HNO3 and trapped in a coil. The carrier transferred the analyte to the sample arm assembly and 20 µL portions of the analyte were deposited into the graphite tube atomizer under control of the AAS computer (details given). The analyte was atomized (temperature program details given) and the absorbance of Mn in the vapor produced was measured at 279.5 nm. The calibration graph was linear up to 15 µg/l of Mn and the detection limit was 0.2 µg/l. Inter- and intra-day RSD (n = 10 and 6, respectively ) were 2.8 and 3.2%, respectively, at ~ 5 µg/l Mn. Recoveries were 95-104%. Results agreed well with those obtained by an atomic absorption chelation-liquid-liquid extraction method.
Manganese Ion exchange Spectrophotometry Dowex Interferences Method comparison

"Flow Injection For The Determination Of Selenium(IV) And Selenium(VI) By Hydride-generation Atomic Absorption Spectrometry With Microwave-oven Online Prereduction Of Selenium(VI) To Selenium(IV)"
Spectrochim. Acta B 1996 Volume 51, Issue 14 Pages 1837-1847
J. L. Burguera, P. Carrero, M. Burguera, C. Rondon, M. R. Brunetto and M. Gallignani

Abstract: The manifold is based on an Ismatec IPC eight-channel peristaltic pump and incorporates the time-based injector, controlled by a Gralab model 900 programmable timer, described previously (Carrero et al., Talanta, 1993, 40, 1967; Burguera et al., Anal. Chim. Acta, 1995, 308, 339), a Prolabo MW Microdigest oven mode l 301, and the gas-phase separator of Burguera etal. (Ibid., 1991, 261, 105). The carrier is 1% HCl and the 0.5% NaBH4 reductant solutions for Se(IV) and Se(VI) are in 4 M and 12 M HCl media, respectively. Further NaBH4 solution is added downstream of the microwave oven to keep the baseline stable. Se is determined at 196 nm. The response is linear for up to 120 µg/l of Se(IV) and 100 µg/l of Se(VI), and the detection limits are 1 and 1.5 µg/l, respectively. The RSD were 2.0-2.5% and the recoveries of Se(IV) and Se(VI) were 96-98% and 94-98%, respectively. The method has been applied to geothermal water and citrus juice.
Selenium Sample preparation Spectrophotometry Microwave Online digestion Speciation Phase separator

"Flow Injection Spectrophotometric Determination Of Trace Amounts Of Bromide By Its Catalytic Effect On The Hydrogen Peroxide Oxidation Of Pyrocatechol Violet"
Anal. Sci. 1988 Volume 4, Issue 3 Pages 273-276

Abstract: Trace amounts of Br- were determined by flow injection analysis, by using a 10-m reaction coil operated at 37°C; 500 µL of sample solution was injected into the water carrier stream, which was then mixed with 3.5 M H2O2 and 0.1 or 0.05 mM catechol violet in 2.3 M HCl, with subsequent detection at 550 nm. The calibration graph was rectilinear from 10 to 600 µg L-1 of Br-; coefficient of variation were 2.5 and 1.4% for 20 and 105 muwg L-1 of Br-, respectively (n = 10), and recovery was 90 to 107%. Many common ions did not interfere, and the interference of others was reduced by using flow injection analysis; I- interfered at 200 µg l-1, but the effect could be decreased by suitable dilution. The method has been applied to several natural waters.
Bromide Spectrophotometry Catalysis Heated reaction Interferences

"Automated System For The Determination Of Total Silica In Geothermal Water By Flow Injection - Spectrophotometric Method"
Bunseki Kagaku 1991 Volume 40, Issue 8 Pages 425-428
Takenaka, T.

Abstract: Sample (20 µL), sandwiched between two 100 µL layers of 0.1 M NaOH, was introduced into a stream of water at 1.3 mL min-1. The polymerized silica in the sample was decomposed to the monomer in 10 m of PTFE tubing at 145°C before the sample was merged with 1% ammonium molybdate - 0.3 M H2SO4. After heating at 90°C, the absorbance of the yellow complex was measured at 400 nm. From 0.5 to 100 mg L-1 of Si could be determined at a sampling rate of 30 h-1. For 50 mg L-1 of Si, the coefficient of variation was 1.5%. The method was applied to the analysis of geothermal waters and colloidal silica samples. Results agreed well with those obtained by the JIS method.
Silica Spectrophotometry Automation Heated reaction

"Flow Injection Analysis Of Silicic Acid In Geothermal Water"
Chinetsu 1985 Volume 22, Issue 1 Pages 9-13
Yokoyama, T.;Tarutani, T.

Abstract: Flow injection analysis (FIA) was developed for the spectrophotometric determination of molybdate reactive silicic acid (MRSA) in the presence of polysilicic acid and applied successfully for the determination of MRSA in geothermal water. A sample solution (~0.07 mL) is introduced into a carrier stream of water via a loop-valve sample injector. The carrier stream meets a acidic molybdate reagent stream from another channel and flows together into a reaction tubing. The temperature of the reaction tubing is maintained at 90°C. Residence time of the sample in the reaction tubing is ~1 min. The absorbance of heteropoly complex is monitored at 450 nm. MRSA with concentrations of <50 ppm Si can be determined at a sampling rate of 36 samples/h. Total silicic acid can be determined by FIA after decomposition of polysilicic acid with an alkali. (SFS)
Silicic acid Spectrophotometry Heated reaction

"Online Total Arsenic Determination In Urine And Geothermal Fluids By Flow Injection-hydride Generation Atomic Absorption Spectrometry With Microwave Oven Sample Mineralization/oxidation"
Rev. Roum. Chim. 1998 Volume 43, Issue 4 Pages 301-308
Burguera, J.L.;Burguera, M.;Danet, A.F.

Abstract: Samples of 0.1-2.0 mL were subjected to microwave acidic mineralization/oxidation and the continuous hydride generation was carried out by mixing downstream the acidified digest with a 150 g L-1 KI + 5 g L-1 ascorbic acid prereducing solution and thereafter with a 1.0% w/v sodium tetrahydroborate(III) solution The detection limits were of 0.2 ng of arsenic. The relative standard deviation (RSD) of the method obtained in ten replicate analyzes of urine and geothermal fluids spiked with arsenic species varied from 2.5 to 4.5%. Recovery values of the arsenic species were in the range 101-102%. This method is applicable to the determination of total arsenic in the urine of unexposed and exposed subjects.
Arsenic, total Spectrophotometry Sample preparation Microwave