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.