We extracted 100-mg biomass samples with 4 mL ethyl acetate/isopropanol/water mixture (60:30:10, v/v/v) [25 (link)]. Qualitative analysis of sphingolipids from evaporated extracts was obtained by examining their mass spectrum using a triple quad mass spectrometer QTRAP 4500 (Sciex) operating in the MRM positive ionization mode as previously described [26 (link)]. For the reversed-phase chromatographic analysis, 10 μL of the lipid extract was injected on a C18 column (the same model as mentioned above). The solvents and gradient elution were identical to that applied for the determination of phospholipids.
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