Simultaneous serum nicotine, cotinine, and trans-3′-hydroxycotinine quantitation with minimal sample volume for tobacco exposure status of solid organ transplant patients

• A rapid LC–MS/MS assay quantitating nicotine and its metabolites was validated.
• We developed this assay using only one-hundred microliter of serum.
• Quantitating both cotinine and 3-OH-Cot is essential to evaluate tobacco exposure

Concentrations of nicotine and its metabolites in blood are indicative of patients’ current tobacco exposure, and their quantifications have been clinically applied to multiple assessments including demonstration of abstinence prior to heart–lung transplantation. For the purpose of transplant evaluation, the laboratory work up is extensive; thereby an assay with minimal sample volume is preferred. We developed and validated a rapid LC–MS/MS assay to simultaneously quantitate nicotine and its major metabolites, Cotinine and trans-3′-OH-cotinine (3-OH-Cot), in serum. 100 μL of serum was spiked with deuterated internal standards and extracted by Oasis HLB solid phase extraction cartridge. Nicotine and metabolites in the reconstituted serum extract were separated by Agilent Eclipse XDB-C8 3.5 μm 2.1 mm × 50 mm HPLC column within 4.7 min, and quantified by MS/MS with positive mode electrospray ionization and multiple reaction monitoring. Ion suppression was insignificant, and extraction efficiency was 79–110% at 50 ng/mL for all compounds. Limit of detection was 1.0 ng/mL for nicotine and 3-OH-Cot, and <0.5 ng/mL for Cotinine. Linearity ranges for nicotine, cotinine and 3-OH-Cot were 2–100, 2–1000, and 5–1000 ng/mL with recoveries of 86–115%. Within-day and twenty-day imprecision at nicotine/cotinine/3-OH-Cot levels of 22/150/90, 37/250/150, and 50/800/500 ng/mL were all 1.1–6.5%. The reconstituted serum extracts were stable for at least 7 days stored in the HPLC autosampler at 5 °C. Our method correlates well with alternative LC–MS/MS methods. We successfully developed and validated an LC–MS/MS assay to quantitate concentrations of nicotine and its metabolites in serum with minimal sample volume to assess tobacco exposure of heart–lung transplant patients.