Establishment Of Hydrophilic Chromatography Retention Index And Its Application In Metabolilte Analysis

Hydrophilic interaction liquid chromatography-mass spectrometry(HILIC-MS)is a complementary technique to reversed-phase liquid chromatography-mass spectrometry(RPLC-MS)and has been widely used to expand the coverage of the metabolome in MS-based metabolomics.However,the use of HILIC retention time(RT)in metabolites annotation is quite limited because of its poor reproducibility.The retention index(RI)is an evaluation scale for measuring the relative retention of solutes,firstly proposed by Kovats and widely used for RT correction in gas chromatography analysis.In recent years,a series of RI systems have been established on RPLC-MS-based analysis.RI as a standardized retention information annotation of metabolite can help to filter false positive identifications and improve the identification of isomers with similar mass spectra.However,few studies have been reported about the application of RI in the HILIC-MS-based metabolomics analysis.In this dissertation,to improve the accuracy of metabolite annotation in HILICMS analysis,the author developed a hydrophilic chromatography retention index construction strategy(HILIC RI)and explored the application of this strategy in metabolite annotation analysis.The major contents are listed as follows:1.Based on the carbon number law of N,N-dimethylethylenediamine(DMED)-labeled fatty acids(C2-C22)on HILIC,we established a linear calibration equation between HILIC RT and carbon number for the calculation of HILIC RI.Compared with previously developed local linear construction method,the developed HILIC RI calculation method is simpler,and RIs of metabolites whose RTs outside the calibrating RT window can also be obtained using the calibration equation.In addition,the HILIC RI strategy showed good reproducibility under the following conditions :(1)analysis between different experiment batches on the same column;(2)analysis between different gradient and sample matrix on the same column and system;(3)analysis between different column batches with the same column ligand.2.On the basis of the first work,we successfully applied HILIC RI strategy to the metabolite annotation in HILIC-MS-based analysis.Through the HILIC RI strategy,the non-standardized retention information was transformed into standardized ones.In this study,we mainly introduced three application cases,including:(1)HILIC RI strategy in HILIC-ESI-orbitrap MS-based metabolomics analysis to correct RT shift;(2)HILIC RI strategy in isomer identification to improve the accuracy of peak matching;(3)HILIC RI strategy in chemical isotope labeling-assisted HILIC-MS analysis to correct the deuterium isotope effects.