The Study Of Correction Of Retention Time Shift For Chromatographic Fingerprints

Chromatography has been established as one of the most important analytical methods in the modern analytical laboratory, and the technology has been widely used in organic chemistry, analytical chemistry, proteomics, genomics and other fields. Especially chromatography coupled with high resolution mass spectrometry is an important measure in modern necessary laboratory, which combine the separation ability of chromatography and molecular structure information with the mass spectrometry. An ideal chromatogram should have complete separation of peak, sufficient signal-to-noise ratio and none background interference, however, the retention time of chromatogram shifted frequently because of many unavoidable random deviations. Here we propose two methods to align chromatograms.The first method makes full use of the hyphenated chromatographic information from both chromatographic and spectral directions, and Fast Fourier Transform cross correlation is then applied to speed up the alignment procedure. After peak detection and width estimation using Haar CWT derivative, the FFT cross correlation was used to calculate the candidate shifts of the chromatogram to be aligned, then we use the mass spectrometry information to validate which the candidate is the optimal peak shift. The advantages of the method are shape preservation for small peaks and reliable alignment result.The second method makes full usage of both the elution characteristics of chromatograms and local similarity in retention time shift. After window size selected, the optimal shift of each point in the chromatogram to be aligned can be obtained by FFT cross correlation when moving the continuous regions. The method can be used to align nonlinear retention time shifts and it will not introduce the artifacts or remove peak points during the alignment procedure. Fast Fourier Transform engine which can reduce the time complexity of the algorithm from O(N2) to O(NlogN), is chosen to increase the speed of the alignment. So the method can be used to deal with the alignment of high-throughput chromatograms with large number of complex samples.