HILIC-MS/MS chromatograms for GalSph and GluSph. Chromatograms of analytes and internal standards in blank (a), analytes and internal standards in blank with internal standard (b), analytes in wild type mouse serum (c), analytes in twitcher mouse serum (d), analytes in twitcher mouse serum in 2 MRM transitions (e), and analytes in LLOQ (f). Retention times of GalSph and GluSph are 3.5 and 3.2 min, respectively. The analytes (m/z 462→282) are shown in blue and internal standards (m/z 467→287) in green. The qualifier MRM transition m/z 462→264 for GalSph and GluSph is shown in red (e).