Development and validation of a liquid chromatography tandem mass spectrometry method for the determination of cannabinoids and phase I and II metabolites in meconium

- A LC-MS/MS method was developed for the determination of cannabinoids in meconium.
- Main THC metabolites, including CarboxyTHC and THC glucuronides are quantified.
- Detection of THCCOOH glucuronide avoids hidrolysis to increase method sensitivity.
- The method was applied to 19 meconium specimens from uncontrolled pregnancies.

A liquid chromatography-tandem mass spectrometry (LC-MSMS) method was developed and fully validated for the determination of Δ9-tetrahydrocannabinol (THC), 11-hydroxyTHC (OHTHC), 11-nor-9-carboxyTHC (THCCOOH), 8-β-11-dihydroxyTHC (diOHTHC), cannabinol, cannabidiol, and THC and THCCOOH glucuronides in 0.25 ± 0.02 g meconium. Samples were homogenized in methanol and subjected to cation exchange solid-phase extraction. Chromatographic separation was performed on a Kinetex C18 column (50 mm × 2.1 mm, 2.6 μm) at 35 °C, with a gradient of 0.1% formic acid in water and acetonitrile at a flow rate of 0.3 mL/min; total run time was 10 min. Two transitions per analyte were monitored in MRM mode. The method was specific and sensitive; LOD was from 1 to 2 ng/g, and LOQ from 4 to 10 ng/g; linearity ranged from 4 to 400 ng/g for all the analytes, except for THC glucuronide (10-400 ng/g); intra-assay, inter-assay and total imprecision were <11.2%, <13.45% and <15.6%, respectively; accuracy ranged from 93.9% to 109.0% of the target concentration; matrix effect, extraction and process efficiency ranged from −26.4% to −71.4%, 49.9% to 69.5% and 14.3% to 45.0%, respectively. The inclusion of THC and THCCOOH glucuronides avoided the need for the hydrolysis process, thus facilitating sample pretreatment. Application of the method to 19 authentic meconium specimens from uncontrolled pregnancies or women suspicious of drug consumption revealed fetal cannabis exposure in 4 newborns. THCCOOH (24.1-288.8 ng/g), diOHTHC (53.2-332.4 ng/g), THC (4.2-7.7 ng/g), CBN (30.7-93.3 ng/g) and CBD (7.1-251.5 ng/g) were detected in all cases; THCCOOH glucuronide (190.2-306.8 ng/g) in 3 cases; and OHTHC (11.9 ng/g) in the remaining one; however, THC glucuronide was not identified in any specimen.