Use of the kinetic plot method to analyze commercial high-temperature liquid chromatography systems. I: Intrinsic performance comparison

The present study aimed at mapping the separation speed potential of a critical pair on commercial high-temperature HPLC (HT-HPLC) supports at elevated temperatures. For this purpose, band broadening and pressure drop measurements were conducted on three different commercial HT-HPLC columns operated at various elevated temperatures but by keeping the same retention factor. The plate height data were subsequently transformed into a plot showing the minimal required analysis time needed to yield a given required effective plate number. For the considered RPLC alkylbenzene separations, it was found that the maximal gain in separation speed of the critical pair that can be obtained by varying the operating temperature from T=30 to 120 degrees C can be expected to be of the order of a factor of 3-4, if using an individually optimized column length for each considered temperature and if no secondary adsorption effects occur at the lower temperature. This gain factor, remaining more or less constant over the most relevant range of plate numbers, largely paralleled the reduction of the mobile phase viscosity accompanying the temperature increase.