Dried blood spots: Liquid chromatography–mass spectrometry analysis of Δ9-tetrahydrocannabinol and its main metabolites

A sensitive and selective HPLC–MS/MS method has been developed for the first time for the analysis of Δ9-tetrahydrocannabinol (the most important active cannabinoid) and its hydroxylated and carboxylated metabolites in human Dried Blood Spots (DBSs). The simultaneous determination of Δ9-tetrahydrocannabinol and its two main metabolites allows assessing the time elapsed after the drug intake and distinguishing between acute or former consumption. This is an important information in specific contexts such as “on street” controls by police forces. DBSs have been chosen as the optimal biological matrix for this kind of testing, since they provide information on the actual state of intoxication, without storage and transportation problems usually associated with classical blood testing. The analysis is carried out on a C8 reversed phase column with a mobile phase composed of 0.1% formic acid in a water/methanol mixture and an electrospray ionisation (ESI) source, coupled to a triple quadrupole mass spectrometer. The method was validated according to international guidelines, with satisfactory results in terms of extraction yields, precision, stability and accuracy. Application to real DBS samples from Cannabis abusers gave reliable results, thus confirming the methodology suitability for roadside testing.

► First method simultaneously analysing THC, THC-OH and THC-COOH in DBS.
► DBS: alternative matrix to the use of whole blood and plasma to monitor Cannabis intoxication.
► Method fully validated on standard solutions and “blank” DBS samples.
► Application to real DBS from Cannabis abusers.
► Reliable results confirming the methodology suitability for roadside testing.