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

delta C-13 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 (R) silica gel cartridge, then derivatised with cysteamine, and then the delta C-13 value of the acetaldehyde-cysteamine derivative was measured by GC-C-IRMS. Using two acetaldehydes with different delta C-13 values, derivatisation experiments were carried out to cover concentrations between 0.009 x 10(-3) and 1.96 x 10(-3) mg . l(-1)) of atmospheric acetaldehyde, and then delta C-13 fractionation was evaluated in the derivatisation of acetaldehyde based on stoichiometric mass balance after measuring the delta C-13 values of acetaldehyde, cysteamine and the acetaldehyde-cysteamine derivative. delta C-13 measurements in the derivertisation process showed good reproducibility (< 0.5 %) for gaseous acetaldehyde. The differences between predicted and measured delta C-13 values were 0.04-0.31% for acetaldehyde-cysteamine derivative, indicating that the derivatisation introduces no isotope fractionation for gaseous acetaldehyde, and obtained delta C-13 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.