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. Author manuscript; available in PMC: 2022 Jan 1.
Published in final edited form as: Mass Spectrom Rev. 2020 Sep 30;41(1):15–31. doi: 10.1002/mas.21659

Figure 4.

Figure 4.

Schematic illustration of a cholestadiene fragment ion with m/z 369.3516 generated from in-source fragmentation of ammonium adduct ions of free cholesterol and CEs. (A) The spectrum of synthetic CE 10:0 detected as an ammonium adduct at m/z 558.5245 in the positive-ion mode of FTMS. (B) The spectrum of human plasma in the positive-ion mode of FTMS. Cholesterol and 2H7-cholesterol are detected as low abundant ammonium adducts having m/z 404.3887 and 411.4326, respectively. Free cholesterol and CEs undergo in-source fragmentation to produce the fragment ion of m/z 369.3516. Some abundant endogenous lipid species are annotated (Reprinted from the supplemental materials of ref. (Gallego, Hojlund, & Ejsing, 2018) with permission from the American Chemical Society, Copyright 2018). (C) Representative scheme of a cholestadiene fragment ion resulted from in-source fragmentation of ammoniated free cholesterol and CEs.