PREDICTION OF COMPREHENSIVE 2-DIMENSIONAL GAS-CHROMATOGRAPHIC SEPARATIONS - A THEORETICAL AND PRACTICAL EXERCISE

Two-dimensional gas chromatography offers an unsurpassed and ordered s eparation combined with a very high peak capacity. Especially when app lied to the separation and quantitative characterisation of complex mi xtures it constitutes a leap forward with respect to state-of-the-art capillary GC. This is realised by the two orthogonal separations to wh ich an entire sample is subjected. However, the selection of the prope r combination of stationary phases and the temperature program is rath er complicated and time consuming. A model is developed to predict whi ch combination of columns is the most appropriate for a specified sepa ration problem. The model is based on calculating retention times and peak widths of the compounds to be separated, on both columns, thus pr edicting the eventual chromatogram. It starts from estimating the rete ntion factors (k) of the compounds at their elution temperatures. This is performed with the help of the (calculated) vapour pressures and t he 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.