Gas chromatography is one of the widely used analytical tools. The applications of gas chromatography include
- Qualitative analysis
- Testing the purity of compounds
- To trace impurities
- Quantitative analysis
- Determination of a mixture of drugs
- Isolation and identification of metabolites
- Identification of compound mixtures.
Qualitative analysis: Here the compounds in a given sample are identified. Qualitative analysis is done by measuring and comparing the retention time of the sample with that of the standard. The retention time for the sample and standard would be the same under identical conditions.
Testing the purity of compounds: When the chromatogram is run, the peaks are checked. Presence of additional peaks is an indication of impure compounds. For this, the chromatogram of the test is compared with that of the standard. Based on the percentage area of the peaks, the percentage of purity can be derived.
To trace impurities: This is similar to the previous step. The additional peaks indicate the presence of impurities. The peak area also helps to determine the percentage of impurities in the test sample.
Quantitative analysis: This is the technique which helps to determine the quantity of the compound in the test sample. This is done by either
a) Direct comparison technique b) By use of calibration curves c) By internal standard method.
Determination of a mixture of components:
This is multicomponent analysis wherein the quantity of each component in the mixture is determined. This procedure is mostly used for quality control of pharmaceutical drugs.
Isolation and identification of metabolites: The biological samples like urine, serum, plasma can be analyzed to identify the metabolites in them.
Identification of compound mixtures.
Some of the pharmacopeias like USP, BP recommend gas chromatography analysis for drugs like diphenhydramine, atropine, antazoline, etc. This is a standard protocol to be followed by industries as part of quality control.