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. 2019 Dec 31;14(12):e0226744. doi: 10.1371/journal.pone.0226744

Fig 1. Mass spectroscopic analyses of nicotine and its metabolites in the urine of electronic cigarette- and mainstream cigarette-exposed mice.

Fig 1

Eight week old male C57BL/6 mice were exposed to electronic cigarette (E-cig) and mainstream cigarette smoke (MCS) for 12 weeks. A total of 24 mice were used for the urine collection for the E-cig exposure protocol (8 mice/group) and 16 mice /group were used for MCS exposure protocol (8 mice/group). For each experimental group, two mice were housed per cage and urine was collected at the indicated time point. LC-MS/MS analyses of nicotine and its metabolites in the urine was performed as described under Methods. Samples were applied on UPLC and eluate were analyzed online using multiple reactions monitoring (MRM) transition. Representative elution profiles of nicotine and its metabolites cotinine, and 3HC, nicotine and cotinine are illustrated in panels A-C respectively. Panel D shows the abundance of total nicotine equivalent (nicotine+cotinine+3HC) in the samples. Insets show area under the curve for each analyte. Values are mean ± SD. *P<0.05 versus E-cig-exposed mice.