“…Liquid-chromatography-coupled tandem mass spectrometric analysis of sphingolipids was performed on an Aqcuity I class UPLC (Waters, Milford, MA, USA) coupled through electrospray ionization (ESI) to a triple-quadrupole-like tandem mass spectrometer (Xevo TQ-S, Waters, Milford, MA, USA) according to previous publications [ 23 , 78 ]. As described, GD2 was analyzed with an Anionoic Polar Pesticide column (5 µm, 150 mm × 2.1 mm, Waters) in MRM mode [ 23 ], whereas all other sphingolipids were separated on a reversed-phase CSH C18 column (2.1 mm × 100 mm; 1.7 μm, Waters) in MRM mode [ 78 , 79 ]. In positive electrospray ionization mode protonated molecular ions of S1P, Cer, Cer1P, HexCer (likely GlcCer), and Hex2Cer (likely LacCer), GM3 and GD3 ions were detected with transitions to the product ion m/z 264 and protonated molecular HexNAc-Hex2Cer (likely GA2), GM2, GD2, Tetraosylceramide (likely GA1 and Gb4Cer), and GM1 ions to the product ion m/z 204.…”