Features of the dependence of gas chromatographic retention indices on a ratio of amounts of target analytes and reference compounds for high capacity capillary columns

Abstract

The dependence of gas-chromatographic retention indices on the ratio of amounts of target analytes
and reference compounds, RI(γ), is one of the main factors determining their inter-laboratory reproducibility.
For partition mode of chromatographic separation such dependence was previously characterized for packed
columns and WCOT columns only with thin films of stationary phases (0.25–0.33 µm). This work continues
characterization of the dependence RI(γ) and devoted to the discussion of the features of manifestation of this
effect for capillary columns of higher capacity compared with previously characterized, namely, the columns
with an inner diameter of 0.53 mm and stationary phase film thickness more than 1 µm.
To characterize the features of manifestation of the dependence RI(γ) three test analyte of different
polarity were chosen. In the case of partition mode of chromatographic separation linearly descending
dependence RI(γ) were revealed for the first time. It is confirmed that the influence of the ratio of amounts of
characterized and reference compounds on the retention indices of analytes is not associated with overloading
of a column. It is stated that variations of the asymmetry of chromatographic peaks of characterized
compounds at the changing of the temperature of gas-chromatographic separation also affect directly on the
type of dependencies RI(γ) for columns of megabore type. Thus, the character of dependencies RI(γ) is affected not only by the mechanism of
 chromatographic separation (adsorption or partition), but also by the
characteristics of the column (column diameter and film thickness), as well as the chemical origin of
characterized components.
The specificities revealed allow clarifying the influence of various factors on inter-laboratory
reproducibility of gas chromatographic retention indices and, therefore, increase the reliability and
unambiguousness of algorithms of chromatographic identification based on these retention parameters.