Modification of inertness test for gas chromatographic systems

Abstract

The previously proposed approach for controlling the inertness of gas chroma to graphic (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 samp les was five). This appro ach was modified with the purpose of increasing the relia bi lity 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 opera tions and minimizing the number of parallel determina ti ons as well as more rational algorithm of data processing was achieved. The essence of the modified appro ach 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-so lu tions 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 nano gram to several nanograms of polar analytes in the chromatographic zone. The results for the test-samples contained some polar constituents (e.g., benzyl alco hol) 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 sorp tion 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.