For the total analysis of a complex sample, like the naphtha, which contains a host of homologues and isomers in widely varying proportions, the efficiency of any single stationary liquid is definitely limited with respect to its power of fractionation, resolution and identification of the components. These deficiencies can be removed by using a pair of stationary liquids, one separating essentially according to vapour pressure and the other predominantly according to structural differentials of the solute molecules in both the stages of fractionation by preparative GC and subsequent resolution of the fractions by analytical GC. By choosing squalane and tetracyanoethylated pentaerythritol as the two stationary liquids, it has been demonstrated that the efficiency of the retention index and its extended concepts, like, ΔI, dI/dT etc., is vastly improved for the identification of hydrocarbon peaks and the interpretation of complex gas chromatograms. This principle can be easily extended to the qualitative and quantitative analysis of complex samples of all other chemical types, provided the choice of the pair of stationary liquids is proper and the desired retention data of the components are available in them.