Determination of carbon isotope ratios of methanol and acetaldehyde in air samples by gas chromatography-isotope ratio mass spectrometry combined with headspace solid-phase microextraction

Isotopic signatures of atmospheric methanol and acetaldehyde have the potential to improve our ability to quantitatively assess their importance in atmospheric chemistry. However, isotopic measurements of atmospheric methanol and acetaldehyde and their individual source and sink processes have been limited. In this study, we examined gas chromatography-isotope ratio mass spectrometry combined with headspace solid-phase microextraction to measure the carbon isotope ratios of methanol and acetaldehyde in air samples. The method enabled us to determine carbon isotope ratios with a precision (1 standard deviation) of +/- 0.6 parts per thousand for 20ml of air sample containing more than 3ppm of methanol and +/- 0.7 parts per thousand for 20ml of air sample containing more than 2ppm of acetaldehyde. Moreover, the applicability of this method to determine isotope ratios of methanol and acetaldehyde emitted from detached plant leaves was demonstrated.