Speciation of arsenic compounds by using ion-pair chromatography with atomic spectrometry and mass spectrometry detection

Chromatography separation of arsenic compounds is important for chemical speciation studies; yet a complete separation of several biologically and environmentally important arsenic compounds has been difficult to achieve on a single column. We report here baseline resolution for arsenate, arsenite, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine, arsenocholine, and tetramethylarsonium ion, by using mixed ion-pair reagents containing 10 mM hexanesulfonate and 1 mM tetraethylammonium hydroxide, as mobile phase. The complete separation of these anionic, cationic and neutral arsenic species on a reversed-phase C-18 column took only 12 min. Inductively coupled plasma mass spectrometry, hydride generation atomic absorption spectrometry and atomic fluorescence spectrometry systems were used for element-specific detection. The speciation technique was successfully applied to studies of urinary excretion of arsenic compounds following one-time ingestion of shrimp. Arsenobetaine ingested from the consumption of shrimp was excreted into urine in its original form; and approximately 70% of the total arsenobetaine ingested was excreted into urine within 37 h after ingestion.