Simultaneous determination of Delta9-tetrahydrocannabinol, 11-hydroxy-Delta9-tetrahydrocannabinol and 11-nor-9-carboxy- Delta9-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, Delta(9)-tetrahydrocannabinol (THC), 11-hydroxy-Delta(9)-tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-Delta(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 x 2 mm i.d., 3 micro m) and acetonitrile-5 mM 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.