Modification of inertness test for gas chromatographic systems

Abstract

The previously proposed approach for controlling the inertness of gas chroma­to­graphic (GC) systems was based on the determination of peak area ratios for polar and non-polar constituents of test-solutions ( S rel = S polar / S non-polar ) for the series of samples obtained by the consequent dilutions (for the 10-times dilutions the number of samp­les was five). This appro­ach was modified with the purpose of increasing the relia­bi­lity of evaluating the minimal quantities of analytes ( m lim ), for which one can neglect the insufficient inertness of GC systems. In addition to that, the simplification of experimental opera­tions and minimizing the number of parallel determina­ti­ons as well as more rational algorithm of data processing was achieved. The essence of the modified appro­ach was the approximation of S rel = f (p m ) data sets with the 3 rd degree polynomials, following by comparing these data with the averaged S rel (with standard deviations) values for the most reproducible S rel values of three test-so­lu­tions with the highest concentrations of test-compounds. It was shown that the limits of the inertness for the WCOT-column (with the standard non-polar polydimethylsiloxane stationary phase) were from the fractions of nano­gram to several nanograms of polar analytes in the chromatographic zone. The results for the test-samples contained some polar constituents (e.g., benzyl alco­hol) which lead to suggesting that the integral manifestations of the insufficient inertness could be caused not only by the influence of chromatographic systems, but also by the sorp­tion of polar analytes on the surfaces of vials used for the dilution of test-samples. The differences in m lim values for the same polar components at the same analytical conditions, when the dilutions were carried out in the glass or polypropylene vials, were revealed. Keywords : Gas chromatography, inertness control for chromatographic systems, mixtures of polar and non-polar analytes, consequent dilutions of test-solutions, insufficient inertness of sample preparation DOI: http://dx.doi.org/10.15826/analitika.2020.24.2.004 Igor G. Zenkevich, Alena I. Desyatova St. Petersburg State University, Institute for Chemistry Universitetskii prosp., 26, St. Petersburg 198504, Russian Federation