University of North Florida
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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

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Les Ebdon

Abbrev:
Ebdon, L.
Other Names:
Address:
Institute of Research in the Applied Natural Sciences, University of Luton, Park Square, Luton, LU1 3JU, UK
Phone:
+44-1582-489-255
Fax:
+44-1582-489-362

Citations 6

"Development Of A New Method For The Separation Of Vanadium Species And Chloride Interference Removal Using Modified Silica Capillaries-DIN-ICP-MS"
Microchem. J. 2004 Volume 76, Issue 1-2 Pages 161-171
Raquel Garcia-Sanchez, Jörg Bettmer and Les Ebdon

Abstract: A new on-line method for the separation of vanadium (IV) and vanadium (V) as well as for the removal of ClO+ mass spectral interference on vanadium determination by quadrupole-ICP-MS has been developed. The sample introduction system consists of a modified fused silica capillary coupled to a direct injection nebuliser (DIN), between the solvent delivery system and the ICP. Fused silica capillaries were treated with different anion and cation exchanger reagents and were tested for the retention of Cl- and the separation of vanadium ions at µg L-1 levels. A suitable strong anion exchanger functional group (3-aminopropyltrimethoxy silane) was selected. Chlorine anions were retained in this anionic capillary and the separation between V(IV) and V(V) was possible in the pH range 2-4. The selections of instrumental ICP-MS conditions for the minimisation of the ClO+ interference were carefully considered. Factors affecting the chromatographic separation such as sample pH, sample flow rate, effect of methanol in the mobile phase and length of the capillary for the separation were optimized. The proposed methodology provides a simple and rapid method for vanadium speciation. A relative detection limit of 12 L-1 (i.e. absolute detection limits of 120 pg) for V(IV) based on peak height measurements was obtained. The relative standard deviation for V(IV) was 2.4% for a 10 µl injection (n=6).

"The Speciation Of Arsenic Compounds"
Chem. Anal. 2002 Volume 47, Issue 2 Pages 179-188
L. Ebdon, S. Fitzpatrick and M.E. Foulkes

Abstract: It is known that arsenic demonstrates species-dependent toxicity. Quantification of elemental species in a sample, rather than determining total element levels alone, provides information that can be utilised in assessing toxicity, bioavailability and potential effects on the environment. High performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) has proved an extremely efficient tool for identification and determination of arsenic species providing limits of detection at µg L-1 levels. Low-pressure ion exchange chromatograph using mini-columns can provide a simple. yet effective, method for rapid screening of samples. Inorganic forms of arsenic can be separated from organic forms within 3 in in with limits of detection at 1.6 and 1.8 mug kg-1, respectively. The increasing use of electrospray techniques to provide structural information has enhanced the ability to distinguish with confidence previously unidentified species.
Speciation Interferences Optimization

"Novel Preconcentration Technique For The Determination Of Trace Elements In Fine Chemicals"
Anal. Proc. 1989 Volume 26, Issue 11 Pages 377-379
Andrea J. Ambrose, Les Ebdon, Philip Jones

Abstract: The trace elements are pre-concentrated as chelates with Chrome Azurol S (I) on to activated carbon. Thus, to a solution of Cu, Fe and Mg in water or aqueous KNO3 (20%), glucose (30%) or sucrose (20%) is added 10 mg of I and the pH is adjusted to 3. Activated carbon (0.5 g; 8 µm) was added, and the pH was increased gradually to 10 by adding dilute aqueous NH3. After agitating the mixture for ~20 min, the sorbent was separated by vacuum filtration, oven dried, scraped off the filter and mixed to a slurry with aqueous 1% Triton- x 100. The elements were then determined by flow injection slurry atomization - ICP-AES. Recoveries were complete for each analyte, but blank values were high.
Metals Copper Iron Magnesium Spectrophotometry Chelation pH Slurry Triton X Preconcentration Activated carbon Surfactant

"Determination Of Arsenic And Selenium In Coal By Continuous-flow Hydride-generation Atomic Absorption Spectrometry And Atomic Fluorescence Spectrometry"
Anal. Chim. Acta 1987 Volume 194, Issue 1 Pages 177-187
Les Ebdon and John R. Wilkinson

Abstract: Powdered coal (0.7 g) was digested with 72% HClO4 with cautious heating (and quenching in iced water if ignition appeared imminent) until all carbonaceous material had dissolved and was then heated under reflux for a further 10 min. After cooling, the solution was transferred, with washing with 5 M HCl, to a 50 mL flask. In order to remove interfering metal ions, portions (10 to 20 ml) of the digest were transferred to a PTFE centrifuge tube and 2 mL of 10% LaCl3 solution was added followed by 1 mL of either 10% NaI solution (for As) or 10% NaBr solution (for Se). The mixture was cooled, centrifuged, and treated with further 10% LaCl3 solution, the supernatant solution was discarded and the ppt. was dissolved in 5 M HCl and diluted to volume Hydride-generation AAS or AFS was used to determine As or Se; the AFS detection limit was 25 or 10 ng g-1, respectively.
Arsenic Selenium Coal Fluorescence Spectrophotometry Interferences

"Cold Vapor Atomic Fluorescence Spectrometry And Gas Chromatography-pyrolysis-atomic Fluorescence Spectrometry For Routine Determination Of Total And Organometallic Mercury In Food Samples"
Analyst 2002 Volume 127, Issue 8 Pages 1108-1114
Les Ebdon, Mike E. Foulkes, Sophie Le Roux and Riansares Muñoz-Olivas

Abstract: Two procedures have been investigated for the quantification of the different forms of mercury in food. A two-stage procedure has been developed to determine firstly total inorganic and organometallic species, and then the full separation of all organomercury species. The procedure involves solubilisation of the samples using alkaline extractions or enzymolysis, followed by the extraction of organic mercury in an organic solvent, preferably a mixture of dichloromethane and hexane (3 2). For the total organic mercury determination, the organic extract is analyzed for total mercury after nitric acid/peroxide digestion, evaporation of the solvent and detection by cold vapor-atomic fluorescence spectrometry. Full organomercury speciation requires a clean-up step before analysis of the final extract in dichloromethane by gas chromatography coupled to a pyrolyser and an atomic fluorescence detector (GC-pyro-AFS). A detection limit of 6 ng L-1, and reproducibility of 2% was achieved for the CV-AFS method; GC-pyro-AFS yielded 200 ng L-1 and 5% for detection limit and coefficient of variation, respectively. Both procedures were validated with the use of various certified reference materials over a wide range of mercury concentrations, and by spiking experiments. The validated methods were tested successfully on a wide range of commercially available food samples.

"Automated Determination Of Sulfide As Hydrogen Sulfide In Waste Streams By Gas-phase Molecular Absorption Spectrometry"
Analyst 1997 Volume 122, Issue 7 Pages 689-693
Les Ebdon, Steve J. Hill, Mohammad Jameel, Warren T. Corns and Peter B. Stockwell

Abstract: A continuous-flow vapor generation method for sulfide determination is described. A sulfide solution, stabilized in 25% sulfide antioxidant buffer (0.5 M NaOH/0.2 M NaBH4/0.2 M sodium citrate), was pumped (7.6 ml/min) and mixed with a stream (2.8 ml/min) of 0.6 M HCl in a gas/liquid separator. The H2S generated was purged from the solution by an air stream (200 ml/min) and introduced into a glass absorption cell, where the absorbance was measured at 200 nm. A diagram of the system used is given. The calibration graph was linear for up to 100 mg/l sulfide, the detection limit was 0.13 mg/l and the throughput was ~90 samples/h. Recoveries of added sulfide were 98-108%. Of 16 ions tested, only Cu, Pb, Zn and As interfered. The method was applied to waste water. The results obtained agreed with those obtained by titrimetry.
Sulfide Waste Spectrophotometry Gas phase detection Method comparison Phase separator Interferences