GasChromatography and Gas Chromatography-Mass Spactrometry
Gas chromatography is a technique used for separation of volatile substances, or substances that can be made volatile, from one another in a gaseous mixture at high temperatures. A sample containing the materials to be separated is injected into the gas chromatograph. A mobile phase (carrier gas) moves through a column that contains a wall coated or granular solid coated stationary phase. As the carrier gas flows through the column, the components of the sample come in contact with the stationary phase. The different components of the sample have different affinities for the stationary phase, which results in differential migration of solutes, thus leading to separation
Martin and James introduced this separation technique in 1952, which is the latest of the major chromatograhpic techniques. However, by 1965 over 18000 publications in gas chromatography (GC) were available in the literature. This is because optimized instrumentation was feasible. Gas chromatography is good only for volatile compounds or those, which can be made volatile by suitable derivatization methods or pyrolysis. Thus, about 20% of chemicals available can be analyzed directly by GC.
Gas chromatography can be used for both qualitative and quantitative analysis. Comparison of retention times can be used to identify materials in the sample by comparing retention times of peaks in a sample to retention times for standards. The same limitations for qualitative analysis discussed in Chapter 26 also apply for separations in GC. Quantitative analysis is accomplished by measurement of either peak height or peak area