High resolution essential oil analysis by using comprehensive gas chromatographic methodology

The new technique of comprehensive gas chromatography (GC x GC) is applied to the analysis of Vetiver essential oil, and the complex nature of the oil components is readily displayed in a two-dimension separation space. The GC x GC method involves the use of two directly coupled columns, with a cryogenic modulation system at their confluence; this allows coeluting peaks from the first column to be zone compressed and pulsed rapidly into the second column and separated. Greater sensitivity of detection is also obtained. Results show that the earlier eluting components from the gas chromatography analysis have similar chemical nature in respect of component polarity, being of low-to-moderate polarity. Later eluting compounds appear to be more polar, and are presumably of an oxygenated nature. Many of these show extensive co-elution, with up to 6-8 overlapping compounds on the first column. These results clearly demonstrate that the complexity of essential oils is much greater than that which might be suspected from single column GC analysis, and also suggest that GC-MS analysis with peak deconvolution capabilities will still probably not be able to adequately identify the interfering components. With GC x GC, minor constituents in the presence of larger components may still be well characterized and quantitated, and from the chromatographic retention patterns their chemical nature might be indicated; this would be aided by establishing the retention behaviour of known compounds. Copyright (C) 2000 John Wiley and Sons, Ltd.