Table 4.

Common fragmentation ions of SP (ESI⁺-mode).

Sphingolipid species	Fragment ion [m/z]
Sphingosine Sphinganine Sphingosine-1-phosphate	264, 266
Cer	264, 266
GlcCer	264, 266
SM	184

Optimal conditions for ionization as well as for collision for each SP species should be determined by representative compounds and/ or internal standard compounds, thus preventing molecular decomposition prior to reaching Q1 and also compensating intrinsic differences in the dissociation rate. Fragment ions of m/z 264 and m/z 266 are indicating a sphingoid base building block (SPB, d18:1, d18:0, respectively), which is representative for most naturally occurring sphingoid base chains. Differentiation of those SP will be achieved by either specification of retention time during liquid chromatography and/or by monitoring the specific fragment ions corresponding to molecular species (108).