Measuring δ13C values of atmospheric acetaldehyde via sodium bisulfite adsorption and cysteamine derivatisation

Abstract

δ13C values of gaseous acetaldehyde were measured by gas chromatograph–combustion–isotope ratio mass spectrometer (GC–C–IRMS) via sodium bisulfite (NaHSO3) adsorption and cysteamine derivatisation. Gaseous acetaldehyde was collected via NaHSO3-coated Sep-Pak® silica gel cartridge, then derivatised with cysteamine, and then the δ13C value of the acetaldehyde–cysteamine derivative was measured by GC–C–IRMS. Using two acetaldehydes with different δ13C values, derivatisation experiments were carried out to cover concentrations between 0.009×10−3 and 1.96×10−3 mg·l−1) of atmospheric acetaldehyde, and then δ13C fractionation was evaluated in the derivatisation of acetaldehyde based on stoichiometric mass balance after measuring the δ13C values of acetaldehyde, cysteamine and the acetaldehyde–cysteamine derivative. δ13C measurements in the derivertisation process showed good reproducibility (<0.5 ‰) for gaseous acetaldehyde. The differences between predicted and measured δ13C values were 0.04–0.31 ‰ for acetaldehyde–cysteamine derivative, indicating that the derivatisation introduces no isotope fractionation for gaseous acetaldehyde, and obtained δ13C values of acetaldehyde in ambient air at the two sites were distinct (−34.00 ‰ at an urban site versus−31.00 ‰ at a forest site), implying potential application of the method to study atmospheric acetaldehyde.