Quantitative aspects of a valve-based, multi-stage multidimensional gas chromatography-infrared spectroscopy-mass spectrometry system

Abstract

Use of high-resolution capillary gas chromatography coupled with infrared and mass spectral detectors is a very powerful qualitative analytical technique. However, accurate qualitative analyses with spectroscopic detection requires that the separation system provide the detectors with pure components. Unfortunately, in very complex mixtures, this is virtually impossible when single-stage separations are employed. This paper describes the sample recycling capabilities of a valve-based multidimensional gas chromatography system equipped with both infrared and mass spectral detectors. Sample recycle efficiencies, valve adsorption effects and cycle-to-cycle reproducibility are considered. Mixtures including the Grob test mixture were analyzed and it was found that 35 out of the 40 total components examined could be recycled six times or more following injection of 500 ng or less of each component. Additionally, the first demonstration of a 23-stage recycling experiment with several components of a chlorinated hydrocarbon mixture is shown. This demonstrates the plausibility of performing GC n experiments, where n is the number of separation stages, with values of n up to 23 for these components. It is also shown that mechanical valves generally do not have deleterious effects on the majority of these components. The main limitations of the system appear to be the design of the heating system and the manual control of the pressure and flow switching systems. The applicability of the present results to qualitative analyses are discussed.