The optimisation of GC x GC and the analysis of diesel petrochemical samples

Abstract

Comprehensive two-dimensional gas chromatography (GC x GC) is a new technique with a promising future in analytical chemistry. Researchers have already shown the advantages of this technique to unravel complex samples consisting of hundreds of compounds. The predominant advantage of GC x GC above conventional one-dimensional gas chromatography is the greatly enhanced peak capacity. To fully utilise this enhanced peak capacity the instrumentation needs to be run at optimum conditions. The optimisation of one-dimensional gas chromatography (GC) is done on a routine basis in analytical laboratories and handbooks are available to cover these optimisation strategies. This study was aimed at providing similar guidelines for GC x GC. Since the underlying theory of GC and GC x GC are essentially the same, conventional GC optimisation strategies were the point of departure for this research. The different operational parameters in GC x GC were identified and emphasis was then placed on a method to simultaneously optimise the flow rate in both columns, taking into consideration the common practice of series-coupling of columns of different internal diameters. The influence of second-dimension stationary phase, temperature program and modulator operation on the distribution and shape of chromatographic peaks in the two dimensions is also investigated. The results obtained from this study provide a useful new approach to optimise a GC x GC system where two gas chromatographic columns of various dimensions are connected in series. The use of diesel samples in this optimisation process presented some useful applications for future research in the petrochemical industry. Examples of potential applications such as “fingerprinting techniques” and compositional analysis are also discussed.