Question

In gas chromatography how can you calculate the relative amount of the compounds that elute out of the column? Please provide a sample and if it possible a sketch

Answer 1

Gas chromatography is a useful technique to identify as well as quantify individual components in a mixture. By the use of chromatographic data one can calculate the relative amount of the compounds that elute out of the column.

There are variouis methods for the concentration calulation which include:

Area percent method , single point external standard , single point internal method , multiple point internal method

AREA percent method

To know the relative amounts of the compounds eluted out of the column, it is assumed that the detector response is similar towards all the compounds which gives a rough estimate and therefore is an easy method.

The relative percentage of the total response gives the relative concentration/amount.

Percent area = area of analyte / sum of area for all the peaks

This indicates the value of analyte in the sample.

OR

Concentration of unknown sample = (sample area of the sample / sample area of the standard) * concentration of standard

For precise concentration one needs to determine the response factor, using standards.