Comparisons of Five Algorithms for Chromatogram Alignment

In this study, five frequently used warping algorithms [correlation optimized warping (COW), recursive alignment by fast Fourier transform (RAFFT), dynamic time warping, variable penalty dynamic warping, and parametric time warping (PTW)] are compared for their ability to align chromatograms with retention time shifts. Five datasets consisting of chromatograms of herbal medicines analyzed by high-performance liquid chromatography (HPLC) (Kudzuvine Root, White Paeony Root, Rehmannia Root, Ligusticum wallichii, Scutellaria baicalensis) are chosen to test these five alignment algorithms. The comparison shows all those five methods have misalignments with different degrees, but the correlations of the aligned data sets are all improved, especially for the data sets that are aligned by segment-wise: COW and RAFFT. After the comprehensive comparison, RAFFT wins the highest score, and then COW follows, whereas PTW is not preferable to align HPLC.