Speciation of submicrogram per liter levels of arsenic in water: On-site species separation integrated with sample collection

Speciation of arsenic is crucial for assessing health implications from ars enic ingestion and for effective removal of arsenic from water. We report a method for the speciation of submicrogram per liter levels of arsenic in w ater. The method incorporates water sample collection with on-site arsenic species separation. The method is based on selective retention of arsenic s pecies on specific solid- phase cartridges followed by selective elution an d hydride generation atomic fluorescence analysis of the arsenic species. T he use of a membrane filter, a resin-based strong cation-exchange cartridge , and a silica-based strong anion-exchange cartridge allows for the speciat ion of particulate arsenic and soluble arsenite, arsenate, monomethylarsona te, and dim ethylarsinate species. Detection limit is on the order of 0.05 mu g/L. The method is suitable for direct water sample collection and on-si te separation of arsenic species by flowing a measured volume of water samp le through the filter and cartridges connected in serial. A particular adva ntage of this approach is to maintain the integrity of original arsenic spe cies in the sample. It overcomes the common problem of instability of arsen ic species after water sampling and during sample storage and handling. App lications of the method are demonstrated to the speciation of arsenic in we ll water, raw (untreated) river water, bottled water, and a standard refere nce material (SRM 1643d). Results agree well with the certified values of t he SRM.