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.