Development of a simultaneous analytical method to determine arsenic speciation using HPLC-ICP-MS: Arsenate, arsenite, monomethylarsonic acid, dimethylarsinic acid, dimethyldithioarsinic acid, and dimethylmonothioarsinic acid

A simultaneous analytical method for six arsenic species was established using high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). Arsenate (iAsV), arsenite (iAsIII), monomethylarsonic acid (MMAV), dimethylarsinic acid (DMAV), dimethyldithioarsinic acid (DMDTAV), and dimethylmonothioarsinic acid (DMMTAV) were separated with an isocratic elute. Additionally, DMDTAV and DMMTAV were synthesized by thiolation of DMAV and identified by electrospray ionization-mass spectrometry (ESI-MS). The developed method was based on a reversed phase C18 column and various eluents such as 50 mM ammonium acetate, 15 mM citric acid, 50 mM formic acid, and 5.0 mM TBAP (i.e., 5.0 mM TBAP, 5.0 mM TBAP with 5% methanol addition, and 5.0 mM TBAP with 5% methanol addition adjusted to pH 7.7) were tested. Six As species were successfully separated and detected in the order iAsIII < DMAV < MMAV < DMMTAV < iAsV < DMDTAV in 5.0 mM TBAP solution with 5% methanol addition adjusted to pH 7.7 within 65 min. Furthermore, LODs and LOQs (μg-As L− 1) were determined as 0.22 and 0.65 for iAsV, 0.06 and 0.19 for iAsIII, 0.08 and 0.24 for MMAV, 0.04 and 0.12 for DMAV, 0.26 and 0.78 for DMDTAV, and 0.15 and 0.44 for DMMTAV, respectively. The method was validated using CRM-TWMW (Trace Metals in Drinking Water Standard) with a recovery of 85.1%. It is expected that the findings from the study will contribute towards the rapid, convenience and simultaneous determination of As species in speciation research.