Measurement of nicotine, cotinine and trans-3′-hydroxycotinine in meconium by liquid chromatography–tandem mass spectrometry

Nicotine (NIC), cotinine (COT) and trans-3′-hydroxycotinine (OHCOT) are the most prevalent and abundant tobacco biomarkers in meconium. We have developed and validated an accurate and precise method for the measurement of these analytes in meconium in which potassium hydroxide is used to digest the meconium sample, followed by solid phase extraction from the liquified sample. The precision of OHCOT, COT and NIC measurements (intra-day and inter-day) were 4.8–10.6%, 3.4–11.6% and 9.3–15.8%, respectively. Evaluation of accuracy indicated bias of −4.0, 2.0 and 0.8% for OHCOT at concentrations of 0.5, 2.5 and 7.5 ng/g. The accuracy estimates for COT at concentrations of 0.5, 2.5 and 7.5 ng/g are 4.0, 4.0 and 5.7%, respectively. For NIC at 2, 10 and 30 ng/g the accuracy was calculated to be 3.0, 5.0 and 5.1%, respectively. The linear range of standard solutions was 0.125–37.5 ng/mL for OHCOT and COT, and 0.75–150 ng/mL for NIC. This method was applied to the analysis of 374 meconium samples from infants of both smoking and nonsmoking mothers. Positive correlations with r2 ≥ 0.63 were observed between NIC and COT, COT and OHCOT, NIC and OHCOT, and NIC and (OHCOT + COT) in these samples.