Gas chromatography–mass spectrometric identification of iodine species arising from photo-chemical vapor generation

Ultraviolet irradiation of aqueous solutions of iodide/iodate ion containing low molecular weight organic acids generates volatile iodine species that are amenable to detection by atomic spectrometry. In the presence of formic, acetic or propionic acids, photo-chemical generation results in the formation of HI, methyl- and ethyl-iodide respectively, the latter two products being directly identified by gas chromatography–mass spectrometry. Deuterium and ¹³C-labeled reagents were employed to elucidate the provenance of the alkyl group. Use of ¹³CH₃–COOH produced ¹³CH₃–I; deuterated acetic acid (D₃C-COOD) resulted in the formation of CD₃–I. These observations indicate direct transfer of the alkyl group from the carboxylic acid to iodide, consistent with the suggestion that the mechanism of synthesis involves radical induced reactions.