Fig. 6: Quantification strategies for sialylated glycosphingolipids in human serum.

a Schematic workflow of two quantification strategies (I) and (II) for sialylated glycosphingolipids (GSLs) in human serum; b Comparison between quantification strategies. The bar graphs display the percentage of species with a coefficient of variation below 35%. This data is derived from quantifying six inter-day extraction replicates, with one measurement per serum extract (Supplementary Data 7); c Concentration of 122 sialylated GSLs in ng/µL serum plotted against sialylated GSL species identified from the volunteer’s serum extracted and measured on two different days, with three replicates per day. This figure demonstrates the reproducibility of the semi-quantification of sialylated GSLs in human serum using the proposed combination of Strategy I and II, where the latter was used for correction in cases where outliers were detected; d Linearity curve representing the relationship between the concentration ratio (concentration of analyte/concentration of internal standard) on the x-axis and the response ratio (peak area of analyte/peak area of internal standard) on the y-axis of nine analytes. The figure includes the lower limit of detection (LLOD) and lower limit of quantification (LLOQ) for each analyte using its corresponding internal standard as 3rd sub-strategy. This curve was used to assess the analytical range and sensitivity for quantifying each analyte. Source data are provided as a Source Data file.