Selective oxidation of formaldehyde to carbon dioxide from high ionic strength solution for carbon-13 analysis by mass spectrometry

Abstract

A method for determining the carbon isotopic composition of sub-milligram to milligram amounts of formaldehyde in high ionic strength aqueous solution has been developed. The procedure involves a highly selective two-step oxidation to CO₂, followed by purging, drying and cryogenic trapping of the CO₂. The ¹³C content of processed samples is determined by mass spectrometry. Calibration of the method with an isotopic standard gave yields in the range 85–92%, while isotopic reproducibility (compared with quantitative combustion) was excellent. It is anticipated that the oxidation procedure will prove useful for the analysis of atmospheric formaldehyde collected by sulphito-based substrates.