EA-Conflo-IRMS联机系统的燃烧转化率漂移及其对碳、氮同位素测定的影响

Changes of the Combustion Transformation Capability for EA-Conflo-IRMS and Their Impacts on Carbon and Nitrogen Isotope Ratio Measurement

Changes were demonstrated which were in combustion transformation capability (CTC) of EA-Conflo-IRMS with measuring time and the relationship of measured carbon and nitrogen isotope ratios with their CTC. Although the CTC generally decreases with measuring time, the CTC displayed no or only a little variation during short period (one day or several day) and marked decrease in CTC occurr only when most Cu in reduction tube were oxidized and the oxidative ability of upper part of combustion tube declined. Moreover, the measured carbon and nitrogen isotope ratios tended to reduce with the declined CTC despite there were some complicated changes in the measured isotope ratios due to the influences of other factors. In order to obtain more precise measurement, a reversed calibration should be performed periodically on the CO2 and N2 reference gases by some standard samples to give out the properly normalized δ-values.