Question

Why is a temperature gradient used in gas chromatography? What effect does increasing the temperature have on eluting compounds?

Answer 1

At lower temperature some components will spend more time in column and bound to stationary phase for longer time, this results in large band broadening and long run time.At higher temperatures, these components spend more time in the mobile (gas) phase, helping them elute faster and minimizing band-broadening. So, the best separations are usually observed for temperature gradients, because the differences in polarity and in boiling points are used here.

Increasing the temperature( high temperature ) decreases the retention time but also decreases the quality of separation and eluting compouds.