Sensitive online speciation analysis of arsenic in biological samples by ambient mass spectrometry

Abstract

As a redox-sensitive and multi-species trace element, the chemical behavior of arsenic in various biological sources was closely related to human health. Direct and sensitive speciation analysis of arsenic from complex matrices is ideally required since it enables obtaining multidimensional information concerning arsenic concentration, existing forms, redox states and molecular structures without sample pretreatment. Herein, an online speciation analysis method allowing molecular characterization of both inorganic (As(III), As(V)) and organic arsenic species (MMA, DMA, AsB and AsC) at trace levels from original bio-matrices (e.g. crayfish, laver and kelp) was developed based on ambient ionization mass spectrometry, namely extraction electrospray ionization-hydride generation-microwave plasma torch-mass spectrometry (EESI-HG-MPT-MS). The novel ambient ionization source of MPT was combined with a hydride generator, resulting in a unique mass spectrum behavior for As. By using a home-made sample introduction device and incorporating a HG-MPT, the sensitivity of analytes and matrix tolerance were significantly improved. The detection limits of As(III), As(V), MMA, DMA, AsB and AsC were 0.01, 0.02, 0.08, 0.08, 0.05 and 0.02 μg kg⁻¹ respectively. An online spike experiment was also conducted, showing a recovery of 94–111%, with an RSD less than 10%. The developed method may play a role in studying the chemical or biological behaviors of arsenic in various environments.