Patent ID: 8145438

Claim:
A method for quantitating a substance to be measured, according to which a substance to be measured is quantitated using a chromatographic mass spectrometer, comprising: a database storing step of storing a database, with which a relative calibration curve is registered showing the relationship between a peak area ratio or a height ratio in the chromatogram of a standard substance to a registered substance and the concentration ratio of the standard substance to the registered substance; an internal standard substance measuring step of measuring an internal standard substance having a known concentration by selecting the same substance as said registered substance as the internal standard substance or selecting a substance having no deuterium atoms substituted for hydrogen atoms as the internal standard substance when said registered substance is a deuterium body where hydrogen atoms are substituted with deuterium atoms so that a mass spectrum of the internal standard substance is gained; an absolute value calculating step of calculating the peak area or the height of an internal standard substance by preparing a chromatogram on the basis of the mass spectrum of the internal standard substance by a processor; a substance to be measured measuring step of gaining a mass spectrum of the substance to be measured by measuring the substance to be measured of which the concentration is unknown; a measured value calculating step of calculating the peak area or the height of the substance to be measured by preparing a chromatogram on the basis of the mass spectrum of the substance to be measured by the processor; and a concentration of a substance to be measured calculating step of calculating the concentration of the substance to be measured on the basis of the relative calibration curve, the peak area or the height of the internal standard substance and the peak area or the height of the substance to be measured by the processor.