Selective generation of substituted arsines-cryotrapping-atomic absorption spectrometry for arsenic speciation analysis in N-methylglucamine antimonate

Abstract

Hydride generation-cryotrapping-gas chromatography-atomic absorption spectrometry (HG-CT-AAS) was applied for arsenic speciation analysis in an injectable drug, N-methylglucamine antimonate. The method employs generation of substituted hydrides and selective hydride generation, which makes possible an analysis of arsenites and arsenates and their mono-, di-, and trimethyl substituted species. Interference of the antimony matrix was eliminated using the T-valve to prevent supply of the stibine interferent to the atomizer. The limits of detection in measured sample solutions were 70 ng L⁻¹ for inorganic arsenate, 42 ng L⁻¹ for mono- and dimethylarsenates and 30 ng L⁻¹ for all the other determined species. Concentrations of all methylated species in all samples were below their detection limits. A significant but different amount of inorganic As was found in different batches of the drug: between 0.9 and 2.3 mg L⁻¹ with 7% to 10% of the content present as the trivalent form. The accuracy was assessed by the comparison of the determined inorganic arsenic content with the total arsenic content determined by the conventional inductively coupled plasma mass spectrometry. Both methods yielded for individual samples equal values within experimental error. The HG-CT-AAS procedure showed good performance with minimum sample pretreatment at low investment and running costs.