Identification and Quantification of Nicotine Biomarkers in Human Oral Fluid from Individuals Receiving Low-Dose Transdermal Nicotine: A Preliminary Study

The objective of this preliminary study was to identify and quantify potential nicotine (NIC) biomarkers in post-exposure oral fluid samples collected from 10 NIC-abstinent human participants administered 7 mg transdermal NIC using liquid chromatography-tandem mass spectrometry (LC-MS-MS). Oral fluid samples were collected prior to NIC patch application and at 0.5 and 0.75 h after patch removal using the Quantisal() oral fluid collection device. The validated LC-MS-MS analyte panel included nicotine-Nbeta-D-glucuronide, cotinine-N-oxide, trans-3-hydroxycotinine, norcotinine, trans-nicotine-1'-N-oxide, cotinine (COT), nornicotine, NIC, anatabine, anabasine, and cotinine-N-beta-D-glucuronide. Analytes and corresponding deuterated internal standards were extracted by solid-phase extraction. NIC and COT concentrations were quantifiable in oral fluid samples collected from 6 of the 10 participants 0.5 h after patch removal and in oral fluid samples collected from 7 of the 10 participants 0.75 h after patch removal. Based on the mean NIC and COT concentrations in oral fluid and plasma for the participants with both quantifiable NIC and COT at the 0.5 and 0.75 h collection times, the oral fluid-plasma ratio was 6.4 for NIC and 3.3 for COT. An ELISA procedure was also validated and successfully applied as a screening tool for these oral fluid samples in conjunction with LC-MS-MS confirmation. An ELISA cut-off concentration of 5.0 ng/mL provided excellent sensitivity for discrimination of COT-positive post-exposure oral fluid samples collected after low-level transdermal NIC exposure and oral fluid samples collected prior to patch application.