Comparative characterization of quantitative gas chromatographic analysis capabilities using basic and modified external standard methods

The known mode of chromatographic quantification by the method of external standard is based on the comparison of average absolute peak areas of analyte(s) for target samp les ( S x ) and additionally prepared external standards ( S stand ). This method is characteri zed by the valuable “sensitivity” of the results in relation to the repeatability of the measured peak areas. In the modified method of external standard, the equal amounts of additional standard are added to the equal amounts of samples; the peak ratios ( S x / S add.stand ) and ( S stand / S add.stand ) are used in the subsequent data processing. This modified external standard method is not described in the contemporary scien tific and teaching literature on gas chromatography. Thus, for the illustration of its advan tages, the results of target analyte quantification in different solvents using basic and modified methods are compa red in the cur rent study. All measurements were carried out by the senior students of the Institute for Chemistry of St. Petersburg State University (Russia) during their practical exercises in gas chromatography. It was shown that the modified external standard method compared with its basic ver sion provided better repeatability of determinations, better precision (lesser systema tic errors) and reduced the overall time expenses due to the lesser quantity of serial ana lyses and the absence of the necessity to reveal and exclude the outliers.