ABSTRACT

A gas chromatographic method for separating CO₂ and N₂O was developed to measure ¹³C/¹²C ratios of atmospheric CO₂. The mixture of N₂O and CO₂, which was condensed out from an air sample, was separated by passing through a column packed with porous silica beads, and only CO₂ was recovered for δ¹³C measurements. It was confirmed that the gas chromatographic separation of CO₂ does not change the δ¹³C value of CO₂. Urban air samples in Tokyo and oceanic air samples in the northwestern Pacific were analyzed by using this method. The δ¹³C value of separated CO₂ was shown to be 0.20 ± 0.03‰ greater than the value obtained when the CO₂-N₂O mixture was directly introduced to the mass spectrometer.