Solute descriptors for characterizing retention properties of open-tubular columns of different selectivity in gas chromatography at intermediate temperatures.

An iteration procedure is used to optimize the solute descriptors for 94 compounds suitable for characterizing the retention properties of open-tubular columns for gas chromatography in the intermediate temperature range of 160-240 degrees C. These solute descriptors are used to calculate the system constants of the solvation parameter model for nine open-tubular columns (SPB-Octyl, HP-5, Rtx-440, Rxi-50, Rtx-OPP, DB-1701, DB-225, HP-Innowax, and HP-88) at increments of 20 degrees C from 160 to 240 degrees C. The optimized descriptors afford a two- to three-fold improvement in the fit to the retention model compared with literature values as determined by the standard deviation of the difference between the model predicted and experimental retention factors (log k). Combining literature values for the system constants at lower temperatures (60-140 degrees C) with those obtained here allowed system maps to be constructed for the nine columns over the full temperature range of 60-240 degrees C. For a wide temperature range the system maps indicate that the relationship between the system constants and temperature is non-linear and that polar interactions are likely to be important in relative and absolute terms to quite high temperatures.