CE-ICP-SFMS and HPIC-ICP-SFMS for arsenic speciation in soil solution and soil water extracts

Abstract

Arsenic speciation in soil solutions and soil water extracts was assessed using two different hyphenated techniques, i.e. ion chromatography inductively coupled plasma sector field mass spectrometry (HPIC-ICP-SFMS) and capillary electrophoresis (CE)-ICP-SFMS. Arsenobetaine (AB), dimethylarsinate (DMA), arsenite As^III, monomethylarsonate (MMA) and arsenate As^V were separated using an anion exchange resin. The CE separation protocol allowed the determination of one more species, namely arsenocholine (AC). A functional make-up flow interface design based on pneumatic nebulization was used for both techniques, allowing stable and dependable operation. The separation time of CE-ICP-SFMS could be significantly reduced by application of hydrodynamic pressure. Addition of isopropanol to the sheath revealed improved sensitivity (factor 3). Excellent detection limits for the arsenic species were in the range of 0.04–0.08 ng g⁻¹ for HPIC-ICP-MS. The detection limits of CE-ICP-SFMS were found to be 2 orders of magnitude higher. Soil solutions and soil water extracts obtained by rhizobox experiments of the hyperaccumulating plant Pteris vittata were investigated. The measurements showed only As^V ranging at concentration levels of 0.3–0.1 µg g⁻¹ and 0.3–0.5 µg g⁻¹ in soil solution and water extracts, respectively.