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. Author manuscript; available in PMC: 2018 Apr 1.
Published in final edited form as: J Am Soc Mass Spectrom. 2016 Oct 26;28(4):608–618. doi: 10.1007/s13361-016-1521-y

Figure 5.

Figure 5

(a) MS2 and (b) MS3 spectra of an unanticipated carbonyl compound identified in saliva. (c) MS3 spectrum of DNPH-derivatized synthetic standard of 3-methyl-2-butenal. Using the classification scheme and authentic internal standards, the compound was identified as 3-methyl-2-butenal (methyl crotonaldehyde).