Simultaneous determination of Δ 9 ‐tetrahydrocannabinol, 11‐hydroxy‐Δ 9 ‐tetrahydrocannabinol and 11‐nor‐9‐carboxy‐ Δ 9 ‐tetrahydrocannabinol in human plasma by high‐performance liquid chromatography/tandem mass spectrometry

A rapid and sensitive method for the simultaneous confirmatory analysis of three forensic most relevant cannabinoids, Δ 9 ‐tetrahydrocannabinol (THC), 11‐hydroxy‐Δ 9 ‐tetrahydrocannabinol (11‐OH‐THC) and 11‐nor‐9‐carboxy‐Δ 9 ‐tetrahydrocannabinol (THC‐COOH), by means of high‐performance liquid chromatography/tandem mass spectrometry (LC/MS/MS) in human plasma was developed and fully validated. Sample clean‐up was performed by automated silica‐based solid‐phase extraction and the separation was carried out using a PhenylHexyl column (50 × 2 mm i.d., 3 µm) and acetonitrile–5 m M ammonium acetate gradient elution. Data were acquired with an API 3000 LC/MS/MS system equipped with a turboionspray interface and triple quadrupole mass analyzer using positive electrospray ionization and multiple reaction monitoring. Two MS/MS transitions for each substance were monitored and deuterated analogues of analytes were used as internal standards for quantitation. The limit of quantitation was 0.8 ng ml −1 for THC, 0.8 ng ml −1 for 11‐OH‐THC and 4.3 ng ml −1 for THC‐COOH and linearity with a correlation coefficient r 2 = 0.999 was achieved up to 100 ng ml −1 for THC and 11‐OH‐THC and 500 ng ml −1 for THC‐COOH. The limits of detection were 0.2 ng ml −1 for THC, 0.2 ng ml −1 for 11‐OH‐THC and 1.6 ng ml −1 for THC‐COOH. The developed LC/MS/MS method was also successfully used for the determination of THC‐COOH‐glucuronide, the phase II metabolite of THC‐COOH. Copyright © 2004 John Wiley & Sons, Ltd.