Determination and speciation of arsenic in drinking water samples by X-ray spectrometry technique

Arsenic is ranked as the first compound in the Substance Priority List 2023 by the Agency for Toxic Substances and Disease Registry (ATSDR). The most prominent entrance to the human body is through drinking water wherein the predominant species are arsenite and arsenate. The more toxic As(III) has rigorously threatened human health worldwide; hence, speciation and separation are the need of the hour. In this article, we have reported a simple method of arsenic speciation by wavelength dispersive X-ray fluorescence (WD-XRF) spectrometer. Valence to core (VtC) electronic transitions, i.e., AsKβ_2,5 fluorescence lines were used for arsenic speciation. This speciation study by WD-XRF entails direct measurement of activated alumina pellets containing arsenate and arsenite species adsorbed from water sample without separation of the trivalent and pentavalent species. This is the first report wherein the X-ray technique has been explored for speciation analysis of arsenic and the biggest advantage of the method lies in its applicability to direct analysis of synthesized nanotubes or other solid-phase extraction sorbents entrapping both the arsenic species. For determination of total arsenic using activated alumina as adsorbent, the most intense AsKα_1,2 analytical lines were used and the instrumental limit of detection and the lower limit of quantification were 0.23 μg/L and 0.89 μg/L, respectively. For speciation, these limits were calculated to be 50 μg/L and 200 μg/L, respectively.