Method for spectrometrically measuring isotopic gas and apparatus thereof

Abstract

A correction curve (FIG.,) is prepared by plotting,CO,concentrations and,CO,/,CO,concentration ratios which are determined on the basis of a calibration curve and,CO,and,CO,absorbances of gaseous samples having the same,CO,/,CO,concentration ratio but known different,CO,concentrations. A gaseous test sample containing,CO,and,CO,as component gases is introduced into a cell, and spectrometrically measured. A,CO,concentration of the gaseous test sample is determined by way of the spectrometric measurement. A concentration ratio correction value is obtained on the basis of the correction curve and the,CO,concentration of the gaseous test sample thus determined. A measured,CO,/,CO,concentration ratio is divided by the concentration ratio correction value thus obtained for correction of the,CO,/,CO,concentration ratio. Thus, the measurement accuracy of the concentration ratios of the component gases can be improved.