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1
University of Aberdeen, Department of Chemistry, Old Aberdeen, AB24 3UE Scotland, UK.
2
University of British Columbia, Department of Chemistry,
Vancouver, British Columbia, Canada V6T 1Z1.
3
University of Alberta, Department of Public Health
Sciences, Edmonton, Alberta, Canada T6G 2G3.
a Address for correspondence to this author at: Environmental Health Sciences Program, Department of Public Health Sciences, 13-103 CSB, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada T6G 2G3. Fax 780-492-0364; e-mail xc.le{at}ualberta.ca
Background: Stability of chemical speciation during sample handling and storage is a prerequisite to obtaining reliable results of trace element speciation analysis. There is no comprehensive information on the stability of common arsenic species, such as inorganic arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid, dimethylarsinic acid, and arsenobetaine, in human urine.
Methods: We compared the effects of the following storage conditions on the stability of these arsenic species: temperature (25, 4, and -20 °C), storage time (1, 2, 4, and 8 months), and the use of additives (HCl, sodium azide, benzoic acid, benzyltrimethylammonium chloride, and cetylpyridinium chloride). HPLC with both inductively coupled plasma mass spectrometry and hydride generation atomic fluorescence detection techniques were used for the speciation of arsenic.
Results: We found that all five of the arsenic species were stable for up to 2 months when urine samples were stored at 4 and -20 °C without any additives. For longer period of storage (4 and 8 months), the stability of arsenic species was dependent on urine matrices. Whereas the arsenic speciation in some urine samples was stable for the entire 8 months at both 4 and -20 °C, other urine samples stored under identical conditions showed substantial changes in the concentration of As(III), As(V), monomethylarsonic acid, and dimethylarsinic acid. The use of additives did not improve the stability of arsenic speciation in urine. The addition of 0.1 mol/L HCl (final concentration) to urine samples produced relative changes in inorganic As(III) and As(V) concentrations.
Conclusions: Low temperature (4 and -20 °C) conditions are suitable for the storage of urine samples for up to 2 months. Untreated samples maintain their concentration of arsenic species, and additives have no particular benefit. Strong acidification is not appropriate for speciation analysis.
The following articles in journals at HighWire Press have cited this article:
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 K. A. Francesconi, R. Tanggaar, C. J. McKenzie, and W. Goessler Arsenic Metabolites in Human Urine after Ingestion of an Arsenosugar Clin. Chem., January 1, 2002; 48(1): 92 - 101. [Abstract] [Full Text] [PDF]
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J. Yoshinaga, A. Chatterjee, Y. Shibata, M. Morita, and J. S. Edmonds Human Urine Certified Reference Material for Arsenic Speciation Clin. Chem., November 1, 2000; 46(11): 1781 - 1786. [Abstract] [Full Text] [PDF]
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