Quantitative and qualitative profiling of endocannabinoids in human plasma using a triple quadrupole linear ion trap mass spectrometer with liquid chromatography

Owing to the large implication of endocannabinoids (ECs) in many physiological and pathophysiological processes, a rapid liquid chromatography/electrospray ionisation triple quadrupole linear ion trap mass spectrometric assay (LC/ESI-QqQ(LIT)) was developed for the detection and characterization of anandamide (AEA), 2-arachidonoyl glycerol (2-AG), virodhamine (VA), noladin ether (2-AGE), and N-arachidonoyl dopamine (NADA) in human plasma. The ECs were extracted from 500 microL of plasma by liquid-liquid extraction (LLE) and separated by using an XTerra C18 MS column (50 x 3.0 mm i.d., 3.5 microm) with gradient elution. The mobile phase was composed of a mixture of acetonitrile, water, and formic acid (0.1%). For confirmatory analysis, an information-dependent acquisition (IDA) experiment was performed with selected reaction monitoring (SRM) as survey scan and enhanced product ion (EPI) as dependent scan. The assay was found to be linear in the concentration range of 0.1-5 ng/mL for AEA, 0.3-5 ng/mL for VA, 2-AGE, and NADA and 1-20 ng/mL for 2-AG using a 0.5 mL aliquot of plasma. Repeatability and intermediate precision were found less than 15% over the tested concentration ranges. The developed method thus provided the rapid, highly sensitive and highly selective requirement for assess quantitation, and identification of ECs in plasma.