Identification of unknown compounds on the basis of retention index data in comprehensive two-dimensional gas chromatography

The identification of unknown compounds in complex samples is very difficult. Comprehensive two-dimensional gas chromatography (GC×GC) provides very good resolution and improved identification reliability. Mass spectrometry is a powerful identification tool and retention index data are another good approach to this end. In this study, a second-order polynomial was used to calculate retention index data based on n-alkanes beyond the region of the ‘isovolatile’ curve in GC×GC, and the results in the 2nd dimension were validated by using the same stationary phase column in one-dimensional GC. To test the usefulness of the method, volatile compounds in a tobacco leaf extract fraction were analyzed using GC×GC, and 60 compounds were identified on the basis of their retention indices.