Patent ID: 6274870
Filing Date: 2001-08-14
Classification: A61B,G01N

Abstract:
A method for spectrometrically measuring an isotopic gaseous test sample containing a plurality of component gases including .sup.12 CO.sub.2 and .sup.13 CO.sub.2, by measuring intensity of light transmitted through the gaseous test sample at wavelengths suitable for the respective component gases, and processing data of the light intensity to determine concentrations of the component gases in the gaseous test sample, the method comprising: a first step of introducing the gaseous test sample into a cell and measuring absorbances of the respective component gases in the gaseous test sample; a second step of determining concentrations and concentration ratios of the component gases in the gaseous test sample on the basis of calibration curves; and a third step of obtaining concentration ratio correction values for the component gases on the basis of the concentrations of the component gases obtained in the second step by using correction curves preliminary prepared by measuring absorbances of the component gases in gaseous samples containing the respective component gases in known concentrations with known concentration ratios, determining concentrations and concentration ratios of the component gases in the gaseous samples on the basis of the calibration curves, and by plotting the thus determined concentrations and concentration ratios of the component gases in the gaseous samples, and respectively dividing the concentration ratios of the component gases obtained in the second step by the concentration ratio correction values for the component gases, thereby correcting the concentration ratios of the component gases in the gaseous test sample.