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
Email: schalk@unf.edu
Website: @unf

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William R. Cullen

Abbrev:
Cullen, W.R.
Other Names:
Address:
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
Phone:
+1-604-822-4435
Fax:
+1-604-822-2847

Citations 5

"Determination Of Urinary Arsenic And Impact Of Dietary Arsenic Intake"
Talanta 1993 Volume 40, Issue 2 Pages 185-193
Xiao-Chun Le, William R. Cullen* and Kenneth J. Reimer,

Abstract: Urine samples (10 ml) were treated with 0.1 g of L-cysteine to obtain the same sensitivity from As(III), As(V), monomethylarsonic acid and dimethylarsinic acid. Portions (0.1 ml) were injected into the carrier stream and mixed with 0.7 M HCl and 0.65 M NaBH4 in 0.1 M NaOH. The AsH3 generated from these four species were passed through a gas-liquid separator and thence to the air - acetylene flame for AAS. A second sample (40 ml) without the cysteine addition was heated in a microwave oven in the presence of 4.5 g of K2S2O8 and 2.7 g of NaOH for five 3 min periods. This converted all arsenic species to As(V) (including arsenobetaine, which was not reduced to AsH3 by NaBH4). The solution was diluted to 50 mL and the total As(V) was determined as before but with 3 M HCl. This method is capable of differentiating between different sources of urinary intake, e.g., occupational exposure and dietary intake.
Arsenic Urine

"Arsenic And Antimony Biomethylation By Scopulariopsis Brevicaulis: Interaction Of Arsenic And Antimony Compounds"
Environ. Sci. Technol. 2000 Volume 34, Issue 11 Pages 2249-2253
Paul Andrewes, William R. Cullen, and Elena Polishchuk

Abstract: The biomethylation of arsenic by the filamentous fungus Scopulariopsis brevicaulis is well documented, and the biomethylation of antimony by this fungus was recently established. However, in all the previous studies each metalloid was studied in isolation. Arsenic and antimony are often associated in the environment, and so an understanding of interactions between these elements is necessary. To this end, S. brevicaulis was grown in media containing mixtures of arsenic and antimony compounds in various proportions, and the principle nonvolatile biomethylation products (trimethylantimony and trimethylarsenic species) in the medium were quantified by using HG-GC-AAS. It was found that the yield of trimethylantimony compounds, obtained from the biomethylation of potassium antimony tartrate, was increased in the presence of sodium arsenite. The production of trimethylarsenic species from sodium arsenite was significantly inhibited in the presence of antimony (either as potassium antimony tartrate or antimony trioxide) at antimony concentrations too low to inhibit growth. This is although arsenic(III), in the absence of antimony, is much more readily biomethylated. That is 1.2-5.3% of added arsenic is biomethylated by S. brevicaulis whereas only 0.0006-0.008% of added antimony(III) is biomethylated over 1 month. Potassium hexahydroxyantimonate had no effect on arsenic biomethylation. The addition of potassium tartrate to cultures did not inhibit arsenic biomethylation. The biomethylation of sodium arsenate was not inhibited as much by antimony compounds. The inhibitory effect of antimony was found to be a function of the ratio of antimony to arsenic rather than the absolute amount of antimony.
Speciation

"Antimony Biomethylation By Scopulariopsis Brevicaulis: Characterization Of Intermediates And The Methyl Donor"
Chemosphere 2000 Volume 41, Issue 11 Pages 1717-1725
Paul Andrewes, William R. Cullen and Elena Polishchuk

Abstract: The filamentous fungus Scopulauiopsis brevicaulis biomethylates inorganic antimony(III) compounds to trimethylstibine, that can be detected in culture headspace gases. Dimethylantimony and trimethylantimony species have been detected in the medium of these cultures, but the origin of these species was controversial. We now show that the dimethylantimony species is a true intermediate on the pathway to trimethylstibine (rather than arising from trimethylstibine oxidation or as an analytical artifact) because no dimethylantimony species are formed on trimethylstibine oxidation, as determined by using HG-GC-AAS. Furthermore, the dimethylantimony and trimethylantimony species can be separated, by using anion exchange chromatography, and so the dimethylantimony species is not an analytical artifact, formed during the hydride generation process. The antimony biomethylation mechanism was further probed by measuring incorporation of the methyl group, from (CD3)-C-13-L-methionine and CD3-D-methionine, into methylantimony species and, for comparison, into methylarsenic species. The percentage incorporation of the labeled methyl group into methylarsenic and methylantimony species was not significantly different. The incorporation from (CD3)-C-13-L-methionine was 54% and 47% for antimony and arsenic, respectively. The incorporation from CD3-D-methionine was 20% and 16% for antimony and arsenic, respectively. It appears that the biomethylation of arsenic and antimony occur by very similar, perhaps identical, mechanisms.
Speciation

"Antimony Biomethylation By The Wood Rotting Fungus Phaeolus Schweinitzii"
Appl. Organomet. Chem. 2001 Volume 15, Issue 6 Pages 473-480
Paul Andrewes, William R. Cullen, Elena Polishchuk, Ken J. Reimer

Abstract: The wood rotting fungus, Phaeolus schweinitzii, efficiently transforms the antimony(III) compounds potassium antimony tartrate and antimony trioxide to nonvolatile dimethylantimony and trimethylantimony species, The organoantimony species were detected in potato dextrose broth media samples by using hydride generation-gas chromatography-atomic absorption spectroscopy (HG-GC-AAS). The average concentrations of trimethylantimony species after 40 days incubation with potassium antimony tartrate were approximately 35 mug, 155 µg and 520 µg Sb/l, for substrate concentrations of 10 mg, 100 mg and 1000 mg Sb/l respectively. Thus, the maximum yield of trimethylantimony species was approximately 0.4%, When antimony trioxide (saturated solution, 4 mg Sb/l) was used as a substrate, the average concentration of trimethylantimony species was 150 µg Sb/l after 40 days. The HG-GC-AAS response for the dimethylantimony species was less than that for the trimethylantimony species; however, quantification was not possible because of the lack of an appropriate standard. In comparison, cultures of P, schweinitzii incubated with 1 mg As/I as sodium arsenite contained approximately 200 µg As/I as trimethylarsenic species, i.e. 20% yield, Biomethylation of antimony(V) was inefficient: cultures contained only 3 µg Sb/l as trimethylantimony species after incubation with 100 mg Sb/l as potassium hexahydroxyantimonate, No organoantimony species were detected in control cultures that contained only medium and inorganic antimony compounds. The identities of the organoantimony species were confirmed by using CC-Mass Spectrometry.
Speciation

"Decomposition Of Organoarsenic Compounds By Using A Microwave Oven And Subsequent Determination By Flow Injection-hydride Generation-atomic Absorption Spectrometry"
Appl. Organomet. Chem. 1992 Volume 6, Issue 2 Pages 161-171
Xiao-Chun Le, William R Cullen*, Kenneth J Reimer

Abstract: Environmentally important organoarsenicals such as arsenobetaine, arsenocholine and tetramethylarsonium ion do not form volatile hydrides under the commonly used analytical conditions on treatment with borohydride and it has been difficult to determine their concentrations without further derivatization. This paper describes a rapid method which completely decomposes and oxidizes these arsenicals to arsenate by using potassium persulphate and sodium hydroxide with the aid of microwave energy. The quantitative decomposition of these species permits their determination at low nanogram levels, by hydride generation atomic absorption spectromety (HG AA). A new hydride generator which has high efficiency and minimum dead volume and therefore is suitable for flow injection analysis (FIA) is also described. A system combining flow injection analysis, online microwave oven digestion, and hydride generation followed by atomic absorption measurement, is developed. This system is capable of performing analysis at a sample throughput of 100-120 per hour. Calibration curves were linear from 10 to 200 ng mL-1 of arsenic and the detection limit was 5 ng mL-1 for a 100- injection or 0.5 ng of arsenic. All ten organoarsenic compounds studied gave arsenate as the decomposition product, which was confirmed by using molybdenum blue photometric measurement.