Rapid on-site separation of As(III) and As(V) in waters using a disposable thiol-modified sand cartridge.

The rapid redox transformation of arsenic (As) species in waters presents a great environmental challenge in the accurate determination of its concentration and toxicity. The motivation of the present study was therefore to develop a method for rapid on-site separation of As(V) and As(III) in various aqueous matrices. The authors synthesized a thiol-modified sand (T-sand) that selectively removed As(III) but did not adsorb As(V). The novel application of this T-sand in a disposable cartridge was able to successfully separate As(V) (37-970 µg L(-1) ) and As(III) (not detected to 488 µg L(-1) ) in 23 groundwater samples collected in areas with naturally occurring As. The As speciation results determined with T-sand separation in the field were consistent with those obtained using high-performance liquid chromatography-atomic fluorescence spectrometry. Furthermore, the T-sand cartridge was applicable in a wide variety of matrices, including groundwater, leachants of the toxicity-characteristic leaching procedure, and extracts from the California waste extraction test; sequential extraction test; and in vitro gastrointestinal extraction. This easy-to-use separation method is especially suitable for routine field monitoring of As speciation.