Assessment of cotinine in urine and saliva of smokers, passive smokers, and nonsmokers: Method validation using liquid chromatography and mass spectrometry

Background: Self-report does not provide complete information about tobacco smoke exposure among users and is not relevant for secondhand exposure detection. Biochemical screening for primary metabolite of nicotine would be useful to validate the smoking status and exposure to secondhand smoke. Aims and Objectives: This study was designed to evaluate the performance of a sensitive and rapid method to verify smoking status among smokers, passive smokers, and nonsmokers by quantification of cotinine in saliva and urine using liquid chromatography and mass spectrometry. Materials and Methods: Cotinine (urine and saliva) levels were measured in 98 participants out of which active users (smoked tobacco users; n = 56) and persons exposed to tobacco smoke (passive smokers; n = 15). Values obtained were compared with nonusers (nonsmokers; n = 27). A simple, rapid, and sensitive method was developed and validated for this purpose. With minimal sample preparation, the current analytical procedure showed a wide detection range (1.1-1000 ng/mL) which made it suitable for analyzing various biological matrices. Results: The mean cotinine levels of urine for smokers, passive smokers, and nonsmokers were 1043.7, 36.63, and 13.6 ng/ml, respectively, while in saliva, it was 327.39, 18.31, and 9.53 ng/ml, respectively. Conclusion: Analysis of variance showed that cotinine levels (urine and saliva) of smokers were significantly higher levels than passive smokers and nonsmokers (P < 0.01). Similarly, passive smokers also had significantly higher cotinine levels (urine and saliva) than nonsmokers (P < 0.001).