Fig. 3.
Fragmentation pattern of free sterols and sterol esters. A: Q-TOF MS/MS spectra of betainylated FSs with the corresponding fragmentation patterns and calculated masses. Fragmentation of the betainyl derivatives of sitosterol, stigmasterol, campesterol, and stigmastanol (internal standard) results in the neutral loss of the sterol moiety along with the accumulation of the betainyl fragment FB at m/z of 118.0859. B: Q-TOF MS/MS spectra of SEs. Fragmentation of the ammonium adducts of SEs leads to the release of the corresponding sterol cation FS. 16:1-cholesterol was used as the internal standard.