Photochemical alkylation of inorganic arsenic Part 1. Identification of volatile arsenic species

Abstract

Volatile arsenic species generated by UV irradiation of aqueous solutions of arsenite in low molecular weight (LMW) carboxylic acid media (formic, acetic, propionic and butyric) were identified using ICP-TOF-MS and GC-MS. Cryogenic trapping-GC-MS reveals that inorganic arsenite can be alkylated to yield AsH₃ in the presence of formic acid, trimethylarsine in acetic acid, triethylarsine in propionic acid and tripropylarsine in butyric acid solutions. Mixed ligand arsenic species such as methylarsine, dimethylarsine, dimethylethylarsine and diethylmethylarsine are also formed when a mixture of acids is used. Using 0.05 mg l⁻¹ As(III) as the test solution in 3.1 M acetic acid, a methylation efficiency of approximately 75% was achieved.