Comparison of two calculation procedures for gas chromatography-mass spectrometry associated with stable isotope dilution

Abstract

Isotope dilution mass spectrometry is a technique that has been shown to be capable of meeting the accuracy and precision requirements of reference methods. In this technique an exact and known amount of a stable isotope of a specific analyte is added to the sample so that peaks for both the analyte and its isotope are present in the mass spectrum. The computer calculates the concentration of the analyte by means of the ratio of the respective peak areas. Two calculation procedures, viz., those of Pickup and McPherson and Colby and McCaman, are described and the mathematical factors affecting the nature of the calibration graph are examined. Six examples were studied.