University of North Florida
Browse the Citations

Contact Info

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

View Stuart Chalk's profile on LinkedIn


Classification: Marine -> shellfish -> oyster

Citations 5

"A Comparison Between ICP-MS And AFS Detection For Arsenic Speciation In Environmental Samples"
Talanta 2000 Volume 51, Issue 2 Pages 257-268
Jose Luis Gómez-Ariza, Daniel Sánchez-Rodas, Inmaculada Giráldez and Emilio Morales

Abstract: Performances of two atomic detectors, Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) arid Atomic Fluorescence Spectrometry (AFS) have been compared for arsenic speciation in environmental samples. Instrumental couplings, based on the use of high performance liquid chromatography (HPLIC), hydride generation (HG), and the two atomic detectors were used for the speciation of arsenite, arsenate, dimethylarsinic acid and monomethylarsonic acid. Optionally, arsenobetaine was also determined using on-line ultraviolet (UV) photooxidation. The detection limits ranging from 0.1 to 0.3 µg L-1 (as As) and the precision > 10% RSD obtained with HPLC-(UV)-HG-AFS were comparable with those obtained with HPLC-(UV)-HG-ICP-MS. Both instrumental coupling were applied to the NRCC-TORT-1 and several environmental samples, such as seawater, freshwater, sediments, bivalves and bird eggs, taken from two areas with different degrees of pollution. No influence of the sample matrix was observed on the results using external calibration and standard additions met:hods, for both coupled techniques.
Arsenate ion Arsenite Arsenoβine Dimethylarsinic acid monomethylarsonic acid Fluorescence Mass spectrometry Sample preparation HPLC Speciation Extraction Method comparison Reference material Interferences Standard additions calibration Optimization

"On-line Preconcentration System For Lead Determination In Seafood Samples By Flame Atomic Absorption Spectrometry Using Polyurethane Foam Loaded With 2-(2-benzothiazolylazo)-2-p-cresol"
Anal. Chim. Acta 2001 Volume 441, Issue 2 Pages 281-289
Valfredo A. Lemos and Sérgio L. C. Ferreira

Abstract: In the present paper, an on-line system for enrichment and determination of lead is proposed. It is based on the chemical sorption of lead(II) ions on a minicolumn packed with polyurethane foam loaded with 2-(2-benzothiazolylazo)-2-p-cresol (BTAC) reagent. After pre-concentration, lead(II) ions are eluted by 0.10 mol L-1 hydrochloric acid solution and determined directly by flame atomic absorption spectrometry (FAAS). Chemical and flow variables as well as effect of other ions were studied. The results demonstrated that lead could be determinate with an enrichment factor of 26 for a sample volume of 7.0 mL and pre-concentration time of 1 min. The detection limit (3 s) was 1.0 µg L-1 and the precision (assessed as the relative standard deviation) reached values of 6.0-0.7% in lead solutions of 10^-500 µg L-1 concentration, respectively. The enrichment factor and the detection limit can be further improved by increasing pre-concentration time without degradation in the efficiency due to the favorable kinetics and low hydrodynamic impedance of the present system. Achieved sampling frequency was 48 samples per hour. The effect of another ions in concentrations agreeing with biological samples was studied. It was found that the proposed procedure has necessary selectivity for lead determination in seafood and other biological samples. The accuracy was confirmed by analysis of the followings certified reference materials: fish tissue IAEA, lobster hepatopancreas NRCC TORT-1 and citrus leaves NIST 1572. Recoveries of spike additions (0.2 or 1.0 µg g-1) to several seafood samples were quantitative (90-107%). These results proved also that the procedure is not affected by matrix interferences and can be applied satisfactorily for lead determination in samples of shrimp, oyster, crab, fish and mussel contaminated by it.
Lead Spectrophotometry Preconcentration Interferences Amberlite Polyurethane foam Solid phase extraction

"Flow-through Microwave Digestion System For The Determination Of Aluminum In Shellfish By Electrothermal Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 7 Pages 501-504
Marco A. Z. Arruda, Mercedes Gallego and Miguel Valcárcel

Abstract: Freeze-dried shellfish tissue (100 mg) was accurately weighed, treated with 25 mL 0.2% HNO3 and the slurry was sonicated for 10 min. Portions (100 µL) of the slurry were injected into a carrier stream of 0.2% HNO3 (0.25 ml/min) of a flow injection system (schematic shown) and mixed with 200 µL 3 M HNO3. The mixed solution was transferred to a digestion coil (200 cm x 0.8 mm i.d.) located inside the microwave oven. When the sample was inside the digestion coil (1.5 min after injection), the microwave oven was switched on at 800 W for 2 min. The digested sample was collected in an autosampler cup for 2 min. Portions (20 µL) were automatically transferred to a GF, mixed with 10 µL 0.01 M Mg(NO3)2 and subjected to a pyrolysis/atomization program (temperature/time details given). The absorbance of the volatiles produced was measured at 309.3 nm for Al by AAS. The calibration graph was linear from 100-1000 µg/l of Al (5-50 µg/l of Al after 20-fold dilution of sample in the flow injection system) and the detection limit was 10 µg/l. The method was used to analyze a standard NIST SRM 1566a oyster tissue sample with inter- and intra-day RSD (n = 12 and 10, respectively) of 4.3 and 14.4%, respectively. Recoveries were ~ 90%. The method was applied to the analysis of five fresh shellfish samples (details given) with an RSD (n = 5) of 3.2-14%.
Aluminum Sample preparation Spectrophotometry Microwave Online digestion Reference material Slurry Volatile generation Volatile generation

"Determination Of Arsenic And Selenium By Hydride Generation Atomic Absorption Spectrometry Using A Gas-liquid Separator And A Dehydration Trap"
Microchem. J. 1996 Volume 53, Issue 1 Pages 18-25
Hisatake Narasaki and Jun-Yan Cao

Abstract: Biological material (0.25 g) was allowed to stand overnight in 3 mL concentrated HNO3, 0.5 mL concentrated H2SO4 and 1 mL 60% HClO4 were added and the mixture was digested under low heat until the fumes of HClO4 subsided. The digests, including siliceous residues, were transferred to a Pt dish with water and evaporated to 2 mL. The residues were dissolved with 5 mL 46% HF, 1 mL 9 M H2SO4 was added and the solution was concentrated to 2 mL. The pH was adjusted to 3.5 with 1 M NH3 and applied to a SPE column (35 cm x 10 mm i.d.) packed with 10 cm Chelex 100 chelating ion-exchange resin and the column was washed with 2 x 10 mL water. For the analysis of As; the column effluents were diluted to 100 mL with water and a 10 mL portion was mixed with 5 mL 6 M HCl. Portions of both acid solutions were introduced into the flow injection hydride generation system (schematic shown) and mixed with a stream of 2% sodium tetrahydroborate(III) solution in a Pyrex mixing coil (16 cm x 2 mm i.d.). The hydride generated was collected in a gas-liquid separator, dehydrated in a dehydration trap and swept into an electrically heated furnace with a carrier stream of N2 (2.5 l/min) by manipulating electromagnetic relays and timers (operating details given). The atomized As and Se species were detected at 193.7 and 196 nm, respectively, by AAS. The detection limits were 0.6 and 1 ng/ml, respectively. Tolerance levels to 10 foreign ions are listed. The method was applied to the analysis of five NIST Standard Reference materials (listed). Results agreed well with certified values.
Arsenic Selenium Spectrophotometry Reference material Chelex

"Determination Of Cadmium By Ion-chromatography Using 10-(2-pyridylazo)-9-phenanthrol As A Post-column Derivatization Reagent"
Bunseki Kagaku 1993 Volume 42, Issue 5 Pages 311-316
Yoshida, T.;Okawa, S.

Abstract: Sample (20 µL) was injected onto a Shimadzu pack IC-Cl column (15 cm x 5 mm) with 0.25 M lactic acid buffer of pH 3.3 as mobile phase (1 mL min-1) and post-column reaction with 0.2 mM 10-(2-pyridylazo)-9-phenanthrol solution containing 5% dioxan - 4% Brij 35 - 0.0198% Na borate - 0.0214% NaOH (0.3 mL min-1) at pH 10.3. Detection was at 545 nm. The calibration graph was rectilinear from 40 to 200 ppb of Cd and the coefficient of variation (n = 6) was 1.3% (for 80 ppb of Cd). The detection limit was 14.5 ppb of Cd. The cited method was applied to the determination of Cd in standard reference oyster tissue.
Cadmium HPIC Post-column derivatization Reference material