Speciation of Arsenic Compounds Using High-Performance Liquid Chromatography at Elevated Temperature and Selective Hydride Generation Atomic Fluorescence Detection

Abstract

Understanding arsenic toxicity and metabolism requires quantitation of individual arsenic species. However, it has been difficult to separate many biochemically and environmentally important arsenic species on a single chromatography column. We have studied the separation of 11 arsenic compounds by using ion pair chromatography at 30, 50, and 70 °C column temperatures. The use of elevated column temperature improved separation efficiency and dramatically reduced chromatographic retention time for arsenobetaine, arsenocholine, tetramethylarsonium, and arsenosugars. On-line microwave derivatization combined with hydride generation and atomic fluorescence spectrometry (HGAFS) was used for detection, which was able to differentiate more toxic from less toxic arsenic species. The speciation technique was successfully applied to a study of metabolism of arseno sugars present in commercial seaweed products. Two uncharacterized arsenic-containing metabolites were detected in urine samples collected 20−33 h after the consumption of the seaweed product. These metabolites did not form hydride without microwave digestion. Up to 90 ng/mL of dimethylarsinic acid was detected in the urine samples collected 25−35 h after the consumption of seaweed, compared to a background level of less than 15 ng/mL in urine samples collected before the ingestion of seaweed. The combined high-temperature ion pair chromatography with selective arsenic detection provided a rapid approach to monitoring metabolism of arsenic compounds.