What happens to the retention time of a compound?

Question

if we increase the temperature of the column in the gas chromatogram? will it increase, decrease or remain the same?

Answer 1

A higher GC column temperature will tend to excite molecules into the gas phase - either because they evaporate more readily, or because they are so energetic that the attractions of the liquid no longer hold them. A high column temperature shortens retention times for everything in the column. This is why too high a column temperature decreases it's resolution.

Hope this helps!!!

Answer 2

The material is already in the gas phase, having been put there by the injector block.  The sample gas is carried by the carrier gas (either helium or nitrogen) through the column material which usually causes compounds to remain associated on it depending on polarity.  The retention time for all compounds will be shortened.  Peaks that are low and spread out will be sharpened, but peaks that are close to each other will tend to start to overlap.