Considerations for for the use of ultra-high pressures in liquid chromatography for 2.1 mm inner diameter columns

The current contribution investigates the effects of viscous heat dissipation in chromatographic columns (with an emphasis on so-called narrow bore columns with an inner diameter of 2.1 mm) using numerical simulations of the temperature and velocity profiles and the resulting band broadening, for the first time at operating pressures up to 2000 bar. When operating columns under well-thermostatted conditions to maintain a constant temperature of the mobile phase, a dramatic increase in plate heights can be observed that voids any advantage one could expect from the possibility to use smaller particles offered by the increased pressure limit. It is also clearly demonstrated that, even when the column is not temperature controlled, the backflow of heat along the wall can causes a significant loss in performance under standard operating conditions in a still air oven. It is found that for operating pressure above 1250 bar, a significant (relative to the typical column performance) contribution to the observed plate height will be caused by viscous heating effects, which increases with increasing temperature dependency of the retention factor. In addition, unprecedented experimental measurements of the temperature effects at an operating pressure up to 2600 bar were performed on a 10 cm long, 2.1 mm ID column showing a dramatic temperature increase up to 60 °C relative to the inlet temperature when using methanol as a mobile phase.