OPTIMIZATION OF TEMPERATURE-PROGRAMMED GAS-CHROMATOGRAPHIC SEPARATIONS .1. PREDICTION OF RETENTION TIMES AND PEAK WIDTHS FROM RETENTION INDEXES

A numerical method is described to predict retention times and peak wi dths of a mixture containing components with known identities in capil lary gas chromatography. The procedure is based on extracting thermody namic values (enthalpy and entropy terms) from Kovats retention indice s. Next, a numerical procedure is developed that uses these data to ca lculate retention times and peak widths on any capillary column contai ning the same stationary phase but with a different phase ratio. The e stimations are based on a sound theoretical basis. The predictions can be performed either in the isothermal or temperature-programmed (sing le- or multi-ramp) mode. In the temperature programs, which cover a br oad temperature range, isothermal plateaus are allowed. Errors in the predictions of retention times are generally less than 4%. Prediction of peak widths under the same conditions can be performed with errors of about 10%. An attractive feature of the approach is, that once the thermodynamic values of the solutes of interest are known, future opti mizations can be performed without the need to perform experimental in put runs. This indicates that the concept can be used for complete off -line simulations and/or optimizations of gas chromatographic separati ons.