University of North Florida
Browse the Citations
-OR-

Contact Info

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

View Stuart Chalk's profile on LinkedIn

Dogfish

Classification: Marine -> fish -> dogfish

Citations 4

"Selective Determination Of Methylmercury By Flow Injection Fast-scan Voltammetry"
Electroanalysis 1998 Volume 10, Issue 13 Pages 926-930
Rebecca Lai, Eva L. Huang, Feimeng Zhou *, David O. Wipf

Abstract: A simple flow injection system, suitable for solution flow rates at microliters-per-minute, was combined with fast-scan voltammetry for selective determination of MeHg+. A thin Hg film was formed at a Pt microelectrode prior to the measurement. Detection of MeHg+ is carried out by measuring the oxidation of MeHg radicals that were generated at the Hg microelectrode. At slow scan rates, the electrogenerated MeHg radicals undergo a follow-up dimerization reaction to form M2Hg2 (ErCi2 mechanism). At fast scan rates, MeHg radicals can be quantitatively reoxidized (reversible electron-transfer). Optimization of the experimental conditions of the system was performed based on studies of the relationship between the scan rate and the dimerization rate of the MeHg radical. Under optimized conditions, detection level of sub-nanomole was obtained with a sample consumption <10 µL, and the concentration. detection limit for MeHg+ at 50 V/s was estimated to be ~0.56 µM. To demonstrate the applicability of this method to automatic analysis, repetitive fast-scan cyclic voltammetry was conducted in conjunction with multiple sample injections. Determination of MeHg+ in the presence of excess inorganic Hg was also conducted. This approach to MeHg+ determination was successfully applied to the analysis of elevated dogfish muscle samples.
Methylmercury ion Voltammetry Electrode Electrode Speciation Optimization Apparatus

"Determination Of Total Mercury In Environmental And Biological Samples By Flow Injection Cold Vapor Atomic Absorption Spectrometry"
Spectrochim. Acta B 1996 Volume 51, Issue 14 Pages 1867-1873
James Murphy, Phil Jones and Steve J. Hill*

Abstract: Samples (~0.25 g) are weighed into 60 mL screw-capped PTFE digestion vessels, and biological samples are treated with 5 mL of HNO3 and 1 mL of H2O2 and environmental samples with 2.5 mL of HNO3, 2.5 mL of H2SO4 and 1 mL of H2O2. The vessels are then sealed and heated in a microwave oven for 1 min at medium power. Each digestate plus 2% HNO3/2% H2SO4 washings is diluted to known volume, the solution is degassed ultrasonically, and a portion is placed in an autosampler phial. A diagram of the manifold is presented; the sample (0.5 ml) is injected into a carrier stream of 3% HCl (12 ml/min) that subsequently merges with a stream of 0.2% NaBH4 solution in 0.05% NaOH (6.7 ml/min), and the liberated Hg is carried to a quartz cell in a stream of Ar. Calibration is effected with standard solutions containing up to 30 or 60 ng/ml of Hg, and the detection limit is 0.1 ng. The results for standard dogfish tissue and estuarine sediment agreed well with the certified values. The method was applied to river sediment and canned tuna.
Mercury Spectrophotometry Sample preparation Reference material Volatile generation

"Determination Of Mercury In Dry-fish Samples By Microwave Digestion And Flow Injection Analysis System Cold Vapor Atomic Absorption Spectrometry"
Food Chem. 1997 Volume 58, Issue 1-2 Pages 169-172
L. Aduna de Paz, A. Alegr&iacute;a, R. Barber&aacute;, R. Farr&eacute; and M. J. Lagarda

Abstract: Flow injection analysis system cold vapor atomic absorption spectrometry (FIAS-CV-AAS) preceded by a wet digestion in a microwave oven, as a method for measuring mercury in fish was studied. The digestion process and conditions of the FIAS (carrier concentration: HCl 3% v/v; reducing agent: SnCl2 2% w/v: filling and injection times: 8 and 25 min, respectively; and sample volumes) were optimized. The analytical parameters of the proposed method (detection limit = 7.7 ng/g; precision intraassay = 6.7%; interassay = 14.0%) demonstrates its adequacy and are similar to the ones (detection limit = 19.4 ng/g; precision intraassay = 11.2%; interassay = 15.9%) obtained using a conventional wet digestion method with HNO3+H2SO4+ V2O5. The accuracy are verified with reference material DORM-1 (dog fish-muscle) NAC-CNRC. Moreover, with the optimized method the risk of losses and contamination is low and it is less time consuming and requires smaller reagent volumes than conventional method. Dried fish samples were wet digested in a microwave oven using a two-step program (4 min at 300 W; 2 min at 600 W) with HNO3 and H2O2. The digested samples were then subjected to flow injection cold vapor AAS. The best signals were achieved using 3% HCl carrier (9 ml/min) and 1% SnCl2 reducing agent (5 ml/min). Measurements were made on a 500 µL sample with use of a Perkin-Elmer model 2380 atomic absorption spectrophotometer in conjunction with a Perkin-Elmer FIAS-100 system. Hg was measured at 253.7 nm with a slit width of 0.7 nm (other parameters are tabulated). The detection limit was 7.7 ng/g of Hg. The intra- and inter-assay RSD were 6.7% and 14%, respectively. The results were compared with those obtained by a conventional method similar to that described by Marts and Blaha (J. Assoc . Off. Anal. Chem., 1983, 66, (6), 1421).
Mercury Spectrophotometry Sample preparation Optimization Reference material Volatile generation Method comparison FIAS-100

"Determination Of Organomercury And Mercury In Environmental Samples By Flow Injection Atomic Fluorescence Spectrophotometry"
Int. J. Environ. Anal. Chem. 1996 Volume 63, Issue 3 Pages 187-193
S. C. Edwardst; C. L. Macleod; W. T. Corns; T. P. Williams; J. N. Lester

Abstract: Environmental samples (dogfish and liver certified reference materials, eel and roach) were digested by heating for 4 h at 60°C with 20% tetramethylammonium chloride in a closed vessel. The digest was extracted with toluene, centrifuged, and the extract was mixed with 1 mL 1 mM cysteine or -thiosulfate. The aqueous phase was analyzed for organomercury by flow injection AFS. Total Hg was determined after microwave digestion of samples with 30% H2O2/HNO3/H2O. Sample (100 µL) was injected into a stream of water which was mixed with a stream (0.4 ml/min) of 25 g/l potassium peroxodisulfate and 1.2 g/l CuSO4 in 0.25 M H2SO4 for oxidation to Hg2+ in a 0.5 mL reaction coil. The flow then merged with a stream (0.5 ml/min) of 100 g/l SnCl2 in HCl for reduction to Hg(O) in a 1 mL reaction coil. The Hg(O) was carried in Ar (after separation in a gas liquid separator) to a hygroscopic tubular membrane for drying and to the AFS instrument. The calibration graph was linear for 5-1000 µg/l methylmercury ions and the detection limit was 2 µg/l. The RSD (n = 10) at 25 µg/l was 3.7%. The calibration graph for inorganic Hg was linear for 0.05-1000 µg/l and the detection limit was 0.02 µg/l. Extraction efficiences were 70-80%.
Mercury Methylmercury ion Fluorescence Sample preparation Sample preparation Reference material Extraction Phase separator Speciation