Optimization in headspace GC/FTIR

Abstract

In recent years GC/FTIR has developed into a valuable complementary technique to GC/MS, yielding additional information especially with respect to the identification of isomeric compounds. A disadvantage of GC/FTIR is its inherent inability to attain the low detection levels of GC/MS. Sensitivity is known to be enhanced when employing headspace GC for the trace analysis of volatile components in a non-volatile matrix. Thus, lower detection limits may be expected in GC/FTIR when using the headspace sampling technique. Nevertheless, very little work on headspace GC/FTIR has been done in the past [1]. Generally speaking, optimization in GC/FTIR means increasing the amount of sample and modifying the chromatographic operating parameters in order to obtain the best compromise between maximum chromatographic resolution and highest S/N ratio of the infrared spectra. Using the equilibrium headspace technique, the chromatographic resolution is influenced most strongly by the volume of gas injected onto the column. In balanced pressure sampling with a long injection period, the total amount of sample may be so large that peak distortion will occur. Therefore, in order to optimize headspace GC/FTIR, information is needed on how the sampling time will influence the chromatographic resolution and the S/N ratio of the spectra. The best possible approach to optimized headspace GC/FTIR utilizes the cryogenic capillary head trapping technique, which allows high preconcentration during long sampling periods without any loss in chromatographic resolution [2].