Determination of cotinine, 3'-hydroxycotinine, and their glucuronides in urine by ultra-high performance liquid chromatography

The measurement of the primary nicotine metabolites, cotinine and trans-3′-hydroxycotinine, is a useful biomarker of nicotine exposure and metabolism genetics for smoking cessation research. Herein is described an ultra-high performance liquid chromatography–tandem mass spectrometry method for the determination of these primary nicotine metabolites in urine. Urine samples were diluted one hundred-fold with water and introduced into an ultra-high performance liquid chromatography triple quadrupole mass spectrometer using positive ion electrospray ionization with multiple reaction monitoring. Levels of urinary nicotine metabolites: cotinine, trans-3′-hydroxycotinine, and their respective glucuronides were determined directly using deuterated internal standards and compared with indirect determination by enzymatic hydrolysis. The assay was applied to a community sample of smokers’ urine (n = 280). The assay demonstrated satisfactory performance (relative standard deviation of 1.6–6.5 percent at the 1000 nanograms per milliliter level and > 98 percent recovery) suitable for application to smoking studies with a run time less than five minutes. The mean (min-max) levels of cotinine and cotinine-glucuronide were 968 (31-3831) and 976 (9-5607) nanograms per milliliter. The mean (min-max) levels of trans-3′-hydroxycotinine and trans-3′-hydroxycotinine-glucuronide were 3529 (13-21337) and 722 (0-4633) nanograms per milliliter. Direct determination of glucuronide metabolites was superior to indirect measurement using enzymatic hydrolysis, where there was evidence of loss of metabolites during sample preparation. A sensitive and selective ultra-high performance liquid chromatography–tandem mass spectrometry assay was successfully developed for the determination of cotinine, trans-3′-hydroxycotinine, and their glucuronides in urine. The rapid and simple sample preparation makes this assay suitable for high throughput studies involving nicotine metabolism phenotype for both cytochrome P450 2A6 and uridine 5′-diphospho-glucuronosyltransferase, smoking prevalence, and cessation studies.