A fast and fit-for-purpose arsenic speciation method for wine and rice

Abstract

This fit-for-purpose method was designed in response to recent and proposed food standards, both international and national, that limit inorganic arsenic rather than total, organic, or individual arsenic species such as arsenite (As^III) and arsenate (As^V). In this method, As^III is intentionally oxidized to As^V with H₂O₂ during sample preparation, converting all inorganic arsenic (the sum of As^III and As^V) to the As^V form. Arsenic species were separated in less than 2 minutes using a short, narrow bore, 5 μm chromatography column. This analysis time is 10× faster than the current FDA regulatory method. The use of O₂ reaction gas with inductively coupled plasma triple quadrupole mass spectrometry (ICP-QQQ with MS/MS capability) avoided spectral interferences and dramatically increased sensitivity, allowing for low volume injections. The small injection volume and modified mobile phase composition mitigate non-spectral interferences such as carbon enhanced ionization. Furthermore, the shortened analysis time significantly increases sample throughput. Validation data from two laboratories demonstrate the method's accuracy and reproducibility of both wine and rice matrices in a single analytical batch.