Kinetic plot equations for evaluating the real performance of the combined use of high temperature and ultra-high pressure in liquid chromatography. Application to commercial instruments and 2.1 and 1 mm I.D. columns.

The use of ultra-high pressure liquid chromatography (UHPLC) with pressures up to 1000 bar and columns packed with sub-2-microm particles combined with high-temperature mobile phase conditions (up to 90 degrees C) is assessed according to the current available instrumentation via constrained kinetic plot equations. It is shown that the gain in separation speed, theoretically expected from high-temperature UHPLC (HT-UHPLC), is significantly reduced when taking into account the existing instrumental constraints (extra-column band broadening, flow-rate and column length limitations). This study also shows that significant improvements could be expected on the current commercial instruments by increasing the flow-rate limit and/or using packing columns with particle size in the range 2.5-3.5 microm instead of the current sub-2 microm. These particles should obviously withstand very high pressure.