Comparison with Gas Chromatography:

It has been observed in our discussion on GC in Unit 7 and preceding discussion on HPLC that both the techniques have many similarities and dissimilarities. A common parameter in two cases is the retention data (retention time tr, relative retention α and separation factor s) that is most useful means of qualitative identification of components in a complex mixture. For quantitative analysis, however, peak height or peak area is measured, the former being suitable for sharp, early eluting peaks where peaks are fully resolved. In both the cases, the stationary phase may be similar but the nature of solute analyte and mobile phases are quite different. Both the techniques are highly sensitive with low detection limits, of the order of 10^-12 to 10^-15 moles which, however, depend on the type of detector used. For example, the use of mass spectrometer (MS) interface may further enhance the sensitivity in both cases. Also, both the techniques are highly reproducible, of the order of 1% and have comparable analysis time (2 to 10 min).