Compounds for expanding the descriptor space for characterizing separation systems

A combination of gas chromatography and liquid–liquid partitions in totally organic biphasic systems is used to determine descriptor values for compounds of low volatility suitable for characterizing open tubular columns at high temperatures. The descriptor database of varied compounds includes several difficult to determine by conventional techniques due to their low water solubility or stability. The descriptor database facilitates an expansion of the descriptor space and compound variation for characterizing separation systems. As an application the descriptor database is used to determine the system constants for SPB-Octyl, HP-5, Rxi-5Sil MS, Rtx-440, and Rtx-OPP for the temperature range 200–300 °C. As an example of the broader affect of temperature on column selectivity the variation of the system constants for Rtx-440 over the temperature range 60–300 °C is described in detail. These studies demonstrate the persistence of polar interactions to the highest temperature studied and that at high temperatures selectivity differences persist for moderately polar stationary phases.