New methods are needed for global lipid profiling due to their complex chemical structures and physicochemical properties that is challenging given a lack of reference standards and mass spectral databases for their structural elucidation. Current mass spectrometry-based lipidomic protocols are hampered by complicated data pre-processing, low sample throughput, deleterious ion suppression, and/or inadequate resolution that may contribute to false discoveries. Herein, we introduce an accelerated data workflow to authenticate ionic lipids from serum ether extracts by multisegment injection-nonaqueous capillary electrophoresis-mass spectrometry (MSI-NACE-MS). An iterative three-stage screening strategy is developed to rigorously filter spurious signals and dataset redundancy when using multiplexed electrophoretic separations with full-scan data acquisition under negative ion mode. This approach enables reliable annotation of more than 260 serum lipids annotated based on their accurate mass and relative migration time, which were reliably measured (median CV ~ 10%) in a cohort of non-alcoholic steatohepatitis patients, including bile acids, fatty acids, lysophosphatidic acids, phosphatidylcholines, phosphatidylinositols, phosphatidylethanolamines and prostaglandins. A mobility map is introduced to characterize diverse lipid classes/sub-classes over a wide polarity range with selectivity complementary to reversed-phase LC and HILIC separations based on differences in their polar head group, number of acyl chains, total carbon chain length, and degrees of unsaturation. MSI-NACE-MS greatly expands the metabolome coverage of conventional aqueous-based CE-MS protocols that is a promising yet largely unrecognized approach for large-scale lipidomic studies.

Nontargeted serum lipid profiling by multisegment injection-nonaqueous capillary electrophoresis-mass spectrometry

ACS Fall 2021

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