Studies on the long-term thermal stability of particulate and monolithic poly(styrene-divinylbenzene) capillaries in reversed-phase liquid chromatography

In the present study, the long-term high-temperature (>80 °C) and temperature programming stability of fused silica capillaries packed with 5 µm PLRP-S 300 Å and monolithic PS-DVB capillaries (both 180 µm id × 6 cm) under reversed-phase conditions has been examined. In isothermal mode, the columns were defined as temperature-stable when a less than 10% change in apparent retention factors (k) and a less than 20% change in “retention time/peak width”-factors (n) of the probe solutes (proteins) were observed after passing 7,500 void volumes of effluent through the columns (about 100 h operation). According to these criteria, the PLRP-S and monolithic capillaries were defined temperature-stable at 100 and 130 °C, respectively. Furthermore, when continuously running temperature programs between 50 °C and the upper temperature limit determined in isothermal mode, virtually no change in k or n were observed on neither of the columns after running more than 35,000 void volumes or 1,600 temperature programs. Additionally, temperature-programmed reversed-phase separations of proteins on both types of capillaries are demonstrated and discussed.