Benefit of running HPLC in high temperature

There are several benefits of running the compounds separation in higher temperature. Besides decreasing the run times, an increase in temperature can have other beneficial effects. As the temperature increases, the viscosity of the mobile phase will decrease, resulting in lower pressures. Lower mobile-phase viscosity also improves diffusion in the chromatographic system, giving narrower peaks. Simultaneously, shorter retention times will generate narrower peaks. Narrower peaks mean taller peaks, assuming the same mass of sample on the column, and thus lower detection limits. And if you are happy to work at the original pressure, you can further reduce the run time by increasing the flow rate with isocratic separations until the original pressure is reached.

Increasing the temperature also increases the compound solubility. When a compound has a low solubility, they may precipitate and clog the column. This can be avoided by increasing the temperature. However one must also take into consideration that compound stability depends on the temperature, especially biological compounds. When the temperature is too high, these compounds may degrade and you will not be able to get a good separation and measurement.

So in many cases, an increase in temperature can have multiple benefits – if adverse selectivity changes are not encountered.