Prediction of comprehensive two-dimensional gas chromatographic separations - A theoretical and practical exercise

Two-dimensional gas chromatography offers an unsurpassed and ordered separation combined with a very high peak capacity. Especially when applied to the separation and quantitative characterisation of complex mixtures it constitutes a leap forward with respect to state-of-the-art capillary GC. This is realised by the two orthogonal separations to which an entire sample is subjected. However, the selection of the proper combination of stationary phases and the temperature program is rather complicated and time consuming. A model is developed to predict which combination of columns is the most appropriate for a specified separation problem. The model is based on calculating retention times and peak widths of the compounds to be separated, on both columns, thus predicting the eventual chromatogram. It starts from estimating the retention factors (k) of the compounds at their elution temperatures. This is performed with the help of the (calculated) vapour pressures and the enthalpic contribution to the activity coefficient as obtained from the Kovats retention indices. Some examples illustrate the usefulness of the model. (C) 1998 Elsevier Science B.V. All rights reserved.