Speciation of Arsenic Metabolite Intermediates in Human Urine by Ion-Exchange Chromatography and Flow Injection Hydride Generation Atomic Absorption Spectrometry

Abstract

Biomethylation is considered as the principal metabolic and detoxification pathway for inorganic arsenic in human. The end products of methylation are less toxic and more readily excreted through urine. Therefore, speciation of metabolites in urine is essential to a better understanding of arsenic metabolism, health effects and detoxification ability of individuals exposed to arsenic through drinking water, food and environmental materials. Speciation of inorganic and methylated arsenic in urine is an analytical challenge and often requires expensive instrumentation. We have applied a relatively inexpensive technique for the separation and analysis of various arsenic species, such as, arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in human urine. The technique is based on ion exchange chromatographic separation followed by flow injection hydride generation atomic absorption spectroscopy (FI-HG-AAS). The detection limit varies from 1.0 to 2.0 µg/L for various species. The technique has been successfully applied to speciation of arsenic metabolite intermediates in urine samples collected from patients in Hajiganj, a serious arsenic affected area in Bangladesh. Arsenite (AsIII) was found to be the major component in the urine from these patients. Our findings from patients in Hajiganj, Bangladesh are presented in this paper. The technique permits us to carry out arsenic speciation in urine, essential for toxicological studies and possible nutritional intervention in combating arsenic poisoning in Bangladesh.