Direct Liquid Injection in Comprehensive Two-Dimensional Gas Chromatography Hyphenated to Quadrupole Time-of-Flight...

Luxury food products such as olive oil, wine, and whisky are highly vulnerable to fraudulent practices. Their chemical complexity, fortunately, provides numerous potential adulteration markers, but unfortunately also necessitates the use of powerful, comprehensive profiling approaches involving detailed methods for sample cleanup and analysis. One technique capable of both targeted marker analysis and untargeted profiling is comprehensive two-dimensional gas chromatography coupled to high-resolution mass spectrometry (GC×GC-HRMS). However, as with other chromatographic methods, this technique typically requires substantial sample preparation to eliminate contaminants, which increases the risk of losing valuable information. To address this issue, a direct-injection GC×GC-HRMS technique was developed for comprehensive quality profiling of whiskies. Multiple injection parameters were optimized to deal with the direct injection of a large series of whiskies with a focus on data quality. Overall, carryover percentages of less than 1.5% were obtained, except for long-chain linear acids, sugar-related compounds, and lignin-related compounds (carryover at most 7.1%, 11.4%, and 18%, respectively). The method demonstrated adequate sensitivity to identify numerous quality marker compounds. The developed method was applied to 59 whiskies, with some samples being measured in multiple sequences to assess method stability. Finally, chemometric analyses proved the data to be of good quality. By employing techniques such as principal component analysis, hierarchical clustering analysis, and partial least squares regression, valuable information was obtained, including insights into the preparation process and prize categorization.