Estimation of Uncertainty of Measurements of Linear Retention Indices with Increasing Temperature of the Capillary Chromatographic Column

A brief review is given of the methods of analysis and the analytical parameters for identifying the components of complex mixtures. Parameters for identification of substances with chromatographic analysis of complex multicomponent mixtures are studied: linear retention indices; and it is shown that in order to ensure the necessary level of reliability of the analysis results, it is necessary to estimate the uncertainty of the measurement of these indices. A general equation for determining the variance of the result of indirect measurements of linear retention indices is obtained. For analysis of mixtures containing both analytes and n-alkanes, and mixtures with a separate content of these components, particular formulations of the general equation are generated. A formula for determining the effective number of degrees of freedom of standard uncertainty is presented, taking into account the correlation of input variables in the measurement equation. Mathematical expressions are derived for calculating the extended uncertainties of an estimate of linear retention indices that take into account correlations of the retention times of adjacent chromatographic peaks. Using methods of interval mathematics, an upper estimate of the standard uncertainty of linear retention indices for the joint presence of analytes and n-alkanes in the analyzed mixture was derived, and a significant decrease in comparison with the specified uncertainty in the analysis of mixtures with a separate content of these components was shown. The correspondence of theoretical and experimental results was established. The results obtained can be used to identify the components of the analyzed mixture when standardizing chromatographic analysis techniques.