Group-type analysis of hydrocarbons provides a highly useful characterization of petrochemical samples. Comprehensive two-dimensional gas chromatography (GCxGC) is known for its capabilities to separate different hydrocarbon types across the two-dimensional chromatographic space. But, processing GCxGC data has its own unique challenges due to the additional dimension and requires specific data analysis tools to automate routine methods.<br/><br/>Multi-type templates with peak sets, integration areas, and polygonal retention regions are flexible and effective structures for GCxGC data analysis. A template records the expected two-dimensional retention-time pattern of targeted analyte peaks. In addition, it contains peak sets, consisting either of individually identified peaks or of peaks in a defined polygonal region of the retention-time plane. Once a template is created, a matching algorithm can be applied to align the template with sample data.<br/><br/>One issue for this approach is that the retention-time region for a chemical group may contain peaks of chemicals not in the group. Moreover, polygons for different chemical groups may overlap. The location and shape of the retention-time region for a chemical group may shift across multiple chromatograms too. Combined with mass spectrometry, constraints can be attached to template peaks and polygons of peak sets to improve accuracy and allow automated adjustments. These rule-based constraints use mass-spectral criteria (such as library search, characteristic ions, spectral match factors) to distinguish between peaks in chemical groups, even for groups that overlap in the retention-time plane. Example applications of petrochemical samples demonstrate that a multi-type template, combined with retention-time pattern matching and spectral constraints, is the basis for routine comprehensive group analysis.

Towards automated data analysis for quantifying hydrocarbon types in petrochemical samples with comprehensive two-dimensional gas chromatography

ACS Fall 2021

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