Supercritical fluid chromatography–mass spectrometry using data independent acquisition for the analysis of polar metabolites in human urine

Abstract

The application of supercritical fluid chromatography with mass spectrometric (MS) detection (SFC–MS) was compared towards generic reversed phase liquid chromatography (RPLC) and hydrophilic interaction liquid chromatography (HILIC) for the analysis of urine with regards of ionization performance and analyte identification. The different chromatographic conditions were characterized with a selected set of 51 metabolites from different classes reported in the Human Metabolome DataBase (HMDB) and previously detected in human urine and/or plasma. SFC using a diol column with a gradient of carbon dioxide (CO2) and methanol with 10 mM ammonium hydroxide as modifier was able to retain and separate 20 polar analytes co-eluting in the RPLC eluent front. In the conditions investigated and compared to HILIC where many metabolites were also co-eluting, SFC showed a different ratio between elution domain and analysis time. Similar peak width and symmetry were observed, while retention time variability was slightly lower compared to that of HILIC (0.15% versus 0.24% and 1.26% for RPLC and HILIC, respectively). In SFC–MS, a significant signal enhancement (2–150 times, average of about 10 times) was measured after post-column make-up addition (MeOH/H2O, 95/5, v/v + 25 mM ammonium acetate) for 28 analytes. Nine analytes measured by LC–MS could not be detected in SFC–MS. Applicability of SFC–MS for metabolomics was investigated with the analysis of urine samples using data independent acquisition (DIA) and more specifically Sequential Window Acquisition of all Theoretical Mass Spectra (SWATH/MS). Using a metabolomics library, 74 metabolites from human urine could be identified in positive mode in a single SFC–MS analysis of 15 min.