Evaluation of the technical variations and the suitability of a hydrophilic interaction liquid chromatography-high resolution mass spectrometry (ZIC-pHILIC-Exactive orbitrap) for clinical urinary metabolomics study.

Although many hydrophilic interaction liquid chromatography-high resolution mass spectrometry (HILIC-HRMS) methods have been developed and applied for untargeted metabolite profiling in clinical metabolomics, according to the literature, the suitability of these HILIC-HRMS methods has not been fully evaluated with respect to their performance when they are subjected to statistical analysis. In this study, using a series of human urine samples we investigated the effect of technical variations on multivariate and univariate analysis of the data collected using a previously developed HILIC-HRMS method for untargeted urinary metabolite profiling in clinical metabolomics. The technical variation introduced by sample preparation was more significant than that produced by the HILIC-HRMS method. By using an orthogonal partial least squares (OPLS) model, subtle fold-changes were accurately measured in the urine samples spiked with (13)C and (15)N isotope labelled amino acids at different concentrations. The robustness of this HILIC method was also evaluated by analysing the obtained data from a single urine sample following manipulation of several primary LC parameters. High reproducibility in the chromatographic performance of three ZIC-pHILIC columns with different batch numbers indicated the reliability of the polymer based zwitterionic stationary phase allowing column replacement without compromising the performance of the method.

Zhang T ，Watson DG 《-》

Evaluation of mobile phase characteristics on three zwitterionic columns in hydrophilic interaction liquid chromatography mode for liquid chromatography-high resolution mass spectrometry based untargeted metabolite profiling of Leishmania parasites.

It has been reported that HILIC column chemistry has a great effect on the number of detected metabolites in LC-HRMS-based untargeted metabolite profiling studies. However, no systematic investigation has been carried out with regard to the optimisation of mobile phase characteristics. In this study using 223 metabolite standards, we explored the retention mechanisms on three zwitterionic columns with varied mobile phase composition, demonstrated the interference from poor chromatographic peak shapes on the output of data extraction, and assessed the quality of chromatographic signals and the separation of isomers under each LC condition. As expected, on the ZIC-cHILIC column the acidic metabolites showed improved chromatographic performance at low pH which can be attributed to the opposite arrangement of the permanently charged groups on this column in comparison with the ZIC-HILIC column. Using extracts from the protozoan parasite Leishmania, we compared the numbers of repeatedly detected LC-HRMS features under different LC conditions with putative identification of metabolites not amongst the standards being based on accurate mass (±3ppm). Besides column chemistry, the pH of the mobile phase plays a key role in not only determining the retention mechanisms of solutes but also the output of the LC-HRMS data processing. Fast evaporation of ammonium carbonate produced less ion suppression in ESI source and consequently improved the detectability of the metabolites in low abundance in comparison with other ammonium salts. Our results show that the combination of a ZIC-pHILIC column with an ammonium carbonate mobile phase, pH 9.2, at 20mM in the aqueous phase or 10mM in both aqueous and organic mobile phase components, provided the most suitable LC conditions for LC-HRMS-based untargeted metabolite profiling of Leishmania parasite extracts. The signal reliability of the mass spectrometer used in this study (Exactive Orbitrap) was also investigated.

Zhang R ，Watson DG ，Wang L ，Westrop GD ，Coombs GH ，Zhang T ... -  《-》

Comparison of underivatized silica and zwitterionic sulfobetaine hydrophilic interaction liquid chromatography stationary phases for global metabolomics of human plasma.

To increase metabolome coverage in global LC-MS metabolomics, often both reversed-phase liquid chromatography (RPLC) and hydrophilic-interaction liquid chromatography (HILIC) are implemented in parallel. However, there is a lack of consensus in the literature on the best HILIC stationary phase to employ for global metabolomics of human biological fluids. The objective of this study was to compare in detail the performance of two commonly employed HILIC phases: zwitterionic sulfobetaine ZIC-HILIC stationary phase and an underivatized silica HILIC stationary phase. During method development, the effect of salt concentration in the mobile phase was also investigated, and 5 mM ammonium acetate was selected. The stationary phases were evaluated using a mixture of 37 polar standards covering a range of logP values (-10 to 3.73), molecular weights (59-776 Da), charges (15 anions, 11 cations, and 11 neutral) as well as 17 lipid standards to understand phospholipid behaviour on the two stationary phases. The criteria used for the comparison included the quality of the chromatographic peak shape, adequate analyte retention, peak separation capability, and metabolite coverage. The zwitterionic ZIC-HILIC column provided better chromatographic performance over the silica stationary phase with 14 standards achieving good quality peaks compared to the 7 with the silica column. Only 2 standards were undetected with the ZIC-HILIC column compared to the 14 undetected with the silica column. In human plasma, 1966 and 1650 metabolites were observed on the ZIC-HILIC column in positive and negative electrospray ionization (ESI) respectively. On the silica HILIC column, 1773 and 2028 metabolites were observed in positive and negative ESI respectively, showing comparable performance of the two phases. Next, the effect of adding 10 mM ammonium phosphate to the samples to improve the analyte peak shape and metabolite coverage was investigated for both ZIC-HILIC and silica HILIC. In contrast with recently reported results for pZIC-HILIC, there was no clear evidence that ammonium phosphate addition was beneficial for human plasma samples. In conclusion, ZIC-HILIC provided better chromatographic performance for polar plasma metabolomics than underivatized silica in terms of chromatographic peak shape and chromatographic resolution, while maintaining comparable metabolite coverage. The addition of ammonium phosphate to human plasma was not beneficial for either of the two stationary phases.

Sonnenberg RA ，Naz S ，Cougnaud L ，Vuckovic D ... -  《-》

Evaluation of coverage, retention patterns, and selectivity of seven liquid chromatographic methods for metabolomics.

Wernisch S ，Pennathur S 《-》

Trace Phosphate Improves ZIC-pHILIC Peak Shape, Sensitivity, and Coverage for Untargeted Metabolomics.

Spalding JL ，Naser FJ ，Mahieu NG ，Johnson SL ，Patti GJ ... -  《-》