Additional standards in quantitative chromatographic analysis features of application

Abstract

The principal reason for low reproducibility of chromatographic peak areas and, hence, the final results
of quantitation, seems to be the partial losses of samples during their injection. The method of its compensation
is considered; it implies replacing the absolute peak areas (Si) with their ratios to peak areas of additional
standards (Si/Sadd.stand.), which should be preliminary added to the samples of interest.
The features of the application of additional standards are considered. They are not identical to those
of internal standards in the same-named method of quantification. The principal differences are i) no restrictions
on the chemical origin of additional standards, ii) no information on their concentrations and calibration
coefficients, like it should be known for internal standards. Sometimes the equality of their amounts in two
samples (external standard), or proportionality in few samples (absolute calibration) should be provided. The
solvents of samples of interest can be used as additional standards. This approach allows dilution of samples
(without control of the dilution ratio), as well as the variations of injected amounts.
The primary processing of experimental data includes measuring peak areas, calculation of ratios
(Si/Sadd.stand.), their averaging, and only after that using the target relations. The modification considered is
recommended preferably for methods of external standard, standard addition, and, little less convenient, absolute
calibration.