Integrated Analytical System for Comprehensive Two-Dimensional Enantio-Gas Chromatography and Low-Pressure Gas Chromatography Mass Spectrometry Utilizing a Switching Valve: Design and Optimization.

An analytical system was developed to perform both comprehensive two-dimensional enantio-gas chromatography mass spectrometry with the second-dimension column working under low-pressure conditions (eGC×LP-GC-QMS) and low-pressure gas chromatography mass spectrometry (LP-GC-QMS) analysis, without any changes to the instrumental setup. This is achieved using a switching valve, which also allows for back-flushing of the first-dimension column, thereby generating a flexible and powerful analytical platform. The eGC×LP-GC-QMS configuration can provide both targeted and untargeted information in a single run. In this research, it is employed for the analysis of 56 pesticides (without considering isomers), with the added capability of the backflush mode, effectively removing high-boiling compounds extracted from the matrix and improving sample throughput and system robustness, without major concerns regarding sample preparation. The first-dimension is a chiral column, which enables the separation of seven enantiomers: acephate, benoxacor, chlorflurecol, dibrom, fipronil, methamidophos, and propetamphos. The second-dimension is a wide-bore column (5 m × 0.53 mm I.D. × 0.53 μm df) operating under vacuum conditions. Thanks to the use of a switching valve, it is possible to directly perform LP-GC-QMS analysis, enabling the investigation of a broader range of compounds in terms of boiling point. The operability range of volatile analytes was evaluated for both configurations by injecting different alkane mixtures: C7-C30 for the eGC×LP-GC-QMS configuration and C7-C40 for the LP-GC-QMS configuration.