Comparative visualization for comprehensive two-dimensional gas chromatography

This paper investigates methods for comparing datasets produced by comprehensive two-dimensional gas chromatography (GC  ×  GC). Chemical comparisons are useful for process monitoring, sample classification or identification, correlative determinations, and other important tasks. GC  ×  GC is a powerful new technology for chemical analysis, but methods for comparative visualization must address challenges posed by GC  ×  GC data: inconsistency and complexity. The approach extends conventional techniques for image comparison by utilizing specific characteristics of GC  ×  GC data and developing new methods for comparative visualization and analysis. The paper describes techniques that register (or align) GC  ×  GC datasets to remove retention-time variations; normalize intensities to remove sample amount variations; compute differences in local regions to remove slight misregistrations and differences in peak shapes; employ color (hue), intensity, and saturation to simultaneously visualize differences and values; and use tools for masking, three-dimensional visualization, and tabular presentation with controls for graphical highlights to significantly improve comparative analysis of GC  ×  GC datasets. Experimental results indicate that the comparative methods preserve chemical information and support qualitative and quantitative analyses.