Solid-phase arsenic speciation using XANES: preservation of arsenic species for reliable and accurate environmental risk assessment

Abstract

ABSTRACT The toxicity, bioavailability, and mobility of the toxic element arsenic (As) vary with oxidation state and the chemical environment. Determining the precise fraction of individual As species as well as the total As content in various matrices is essential for evaluating the potential risk of As contamination. We present a synchrotron X-ray absorption spectroscopic study to characterise As species in a total of 14 different matrix certified reference materials (CRMs) and candidate materials of Korea Research Institute of Standards and Science (KRISS) include sediments, ash, ore tailings, seafood, commodity plastics, and cosmetic products. The validity of the method was evaluated by comparison with the results obtained using routinely applied extraction-based sample preparation and ion chromatography-inductively coupled plasma mass spectrometry for speciation analysis. Our study of the As K-edge fine structure with linear combination fitting revealed details of both the composition and distribution of As species in intact solid samples. The key advantage of the present method is its capability to selectively and non-destructively probe As species with minimal risk of species transformation, thus complementary to more popular extraction-based analytical methods. Depending on the sample matrices and origins the investigated CRMs showed distinct As species compositions, the spatial distribution of which was also investigated. This study proposes that X-ray absorption measurement has the potential to determine the native fractions of individual elemental species.