title: Effectiveness of Global, Low-Degree Polynomial Transformations for GCxGC Data Alignment.
abstract: As columns age and differ between systems, retention times for comprehensive two-dimensional gas chromatography (GCxGC) may vary between runs. To properly analyze GCxGC chromatograms, it often is desirable to align the retention times of chromatographic features, such as analyte peaks, between chromatograms. Previous work by the authors has shown that global, low-degree polynomial transformation functions, namely affine, second-degree polynomial, and third-degree polynomial, are effective for aligning pairs of two-dimensional chromatograms acquired with dual second columns and detectors (GC×2GC). This work assesses the experimental performance of these global methods on more general GCxGC chromatogram pairs and compares their performance to that of a recent, robust, local alignment algorithm for GCxGC data [ Gros Anal. Chem. 2012 , 84 , 9033 ]. Measuring performance with the root-mean-square (RMS) residual differences in retention times for matched peaks suggests that global, low-degree polynomial transformations outperform the local algorithm given a sufficiently large set of alignment points, and are able to improve misalignment by over 95% based on a lower-bound benchmark of inherent variability. However, with small sets of alignment points, the local method demonstrated lower error rates (although with greater computational overhead). For GCxGC chromatogram pairs with only slight initial misalignment, none of the global or local methods performed well. In some cases with initial misalignment near the inherent variability of the system, these methods worsened alignment, suggesting that it may be better not to perform alignment in such cases.
authors.affiliation: University of Nebraska, Lincoln , Lincoln Nebraska 68588-0115, United States.
authors.forename: Davis W
authors.initials: DW
authors.lastname: Rempe
authors.affiliation: University of Nebraska, Lincoln , Lincoln Nebraska 68588-0115, United States.|GC Image, LLC , Lincoln Nebraska 68505-7403, United States.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Reichenbach
authors.affiliation: GC Image, LLC , Lincoln Nebraska 68505-7403, United States.
authors.forename: Qingping
authors.initials: Q
authors.lastname: Tao
authors.affiliation: Università degli Studi di Torino , I-10125 Torino, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Cordero
authors.affiliation: Honeywell UOP , 25 East Algonquin Road Des Plaines, Illinois 60017-5016, United States.
authors.forename: Wayne E
authors.initials: WE
authors.lastname: Rathbun
authors.affiliation: Universidade Federal do Rio Grande do Sul , 91501-970 Porto Alegre, Rio Grande do Sul, Brazil.
authors.forename: Cláudia Alcaraz
authors.initials: CA
authors.lastname: Zini