Unsupervised parameter optimization for automated retention time alignment of severely shifted gas chromatographic data using the piecewise alignment algorithm

• Published in: Journal of Chromatography A 2007-02, Vol.1141 (1), p.106-116
• Main Authors: Pierce, Karisa M., Wright, Bob W., Synovec, Robert E.
• Format: Article
• Language: English
• Subjects: Algorithms; Analytical chemistry; Applied sciences; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography, Gas; Correlation coefficient; Crude oil, natural gas and petroleum products; Energy; Exact sciences and technology; Fuels; Gas chromatographic methods; Gas chromatography; Gasoline - analysis; Pattern Recognition, Automated; Piecewise alignment; Principal Component Analysis; Prospecting and production of crude oil, natural gas, oil shales and tar sands; Time Factors; Unsupervised retention time alignment
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2006.11.101

Simulated chromatographic separations were used to study the performance of piecewise retention time alignment and to demonstrate automated unsupervised (without a training set) parameter optimization. The average correlation coefficient between the target chromatogram and all remaining chromatograms in the data set was used to optimize the alignment parameters. This approach frees the user from providing class information and makes the alignment algorithm applicable to classifying completely unknown data sets. The average peak in the raw simulated data set was shifted up to two peak-widths-at-base (average relative shift = 2.0) and after alignment the average relative shift was improved to 0.3. Piecewise alignment was applied to severely shifted GC separations of gasolines and reformate distillation fraction samples. The average relative shifts in the raw gasolines and reformates data were 4.7 and 1.5, respectively, but after alignment improved to 0.5 and 0.4, respectively. The effect of piecewise alignment on peak heights and peak areas is also reported. The average relative difference in peak height was −0.20%. The average absolute relative difference in area was 0.15%.