Fig. 4.

Normalization to standard reference sample effectively removes method-dependent quantitative bias, represented as differences from the average measured concentration. Normalization is independent of lipid concentration. Left side shows large differences in lipid concentrations measured by different sample introduction methods, which are removed after normalizing to a common reference sample. See supplemental Fig. S4 for species-specific depiction. Only lipids detectable with more than one sample introduction method are shown.