Drug testing is used to detect the level of drug abused by an individual.  Techniques employed in the drug testing are immuno assay technique which is used in screening for presence of drugs and gas chromatography/ mass spectrometry in quantitative analyzes. In quantitative analyzes gas chromatography is performed first. This is one of the widespread confirmative test in chemical analyzes.

The principle behind gas chromatography is that it split all components from the sample and provides delegate output. The sample is introduced in to the gas chromatography column via injection port. The sample is then vaporized inside the instrument and the components are separated. The output is obtained in the form of peaks on a paper. Peak represents the amount of substance in the sample.

Sample used for drug testing is the urine sample. GC consists of inert gas which carries the urine sample to the column where components in the sample are separated by boiling temperature and likeness for the column. Retention time is the time elapse between the sample injection and elution of the sample. This retention time helps in identification of the components.

GC analyzes is quite costly and requires well practiced to handle the instrument. Scientific professional can handle the instrument properly and produce the report with out any error. GC has certain limitations in detecting the drugs. Not all the drug produces the similar peak. If a drug crosses the limitation will produce the maximum peak only. Moreover the report changes from instrument to instrument.

Gas chromatography technique is employed in most of the drug testing such as urine test for nicotine, cocaine urine test, methadone urine drug test, barbiturate urinalysis, and in amphetamine drug testing. These tests with the aid of gas chromatography technique will provide you the accurate result in lab.