Experimental and Pre-Analytical Considerations of Endocannabinoid Quantification in Human Biofluids Prior to Mass Spectrometric Analysis

The quantification of endocannabinoids in biological fluids is becoming increasingly popular as an indicator of psychological and physiological function. Numerous methods to quantify the endocannabinoid ligands have been published so far, yet their concentrations and responses often exhibit significant variability across studies. Endocannabinoids regulate and interact with a wide range of biomolecules, causing their concentrations to vary between cohorts of individuals, and sensitivities to them depend on pre-experimental behaviours and activities. Moreover, matrix effects produced by the complex nature of biofluids necessitate rigorous sample preparation techniques, all of which introduce opportunities for both inter- and intra-assay variability. This review aims to address the causes of variability prior to mass spectrometric analysis, including biofluid choice, human variability, sample collection and extraction methods. If these factors are fully considered and standardised methods are introduced, endocannabinoid concentrations may become more reliable, allowing their utility as clinical markers to progress.