Question

Describe “purge and trap” in analytical separation. How does it work, and why is it effective for only the lighter components of crude oil mixture?

Answer 1

Purge and trap are techniques of separating volatile organic compounds (VOCs) and readily absorbable/adsorbable compounds respectively.

In purging, an inert gas is passed through a organic compounds containing purie, in this case the crude oil mixture, wherein the VOCs are carried along with the inert gas carrier. Whereas in trapping, a substrate is used to contain the selectively absorbable or adsorbable compound is absorbed/adsorbed on the substrate when the organic purie (crude oil) is passed through the test tube. In both cases, one set of compounds is preferentially separated from the other.

As both purging and trapping involve pressure driven flow of the mixture, only lighter fractions which are low in weight can be either vaporized (being volatile) or conveniently adsorbed (being light in weight) on a substrate. Hence the observation.