A rapid capillary electrophoresis method with LED-induced native fluorescence detection for the analysis of cannabinoids in oral fluid

Abstract

In the present study, a capillary electrophoresis method with native fluorescence detection for the quantification of two main marijuana cannabinoids, tetrahydrocannabinol (THC) and cannabidiol (CBD), in oral fluid is described. The reported CE method makes it possible to assess illegal cannabis use in approximately 10 min, including saliva sample collection, pre-treatment procedures and capillary electrophoresis (CE) analysis. The proof of the principle, demonstrated on a home-made lab scale instrument, has potential to be easily translated onto a truly portable instrument for on-site measurements. The saliva sample collection/preparation/pre-concentration procedure was combined into one step using a Salivette® sampling device. No separate precipitation of proteins and/or derivatisation was required. The baseline CE separation of the two cannabinoids was achieved in less than 7 min by applying a non-aqueous background electrolyte (BGE), composed of 2.5 mM sodium hydroxide in a methanol–acetonitrile mixture (1 : 1). Cannabinoids were detected at their second λ_ex/λ_em maximum (280/307 nm) with LOD values of 0.19 and 0.17 μg mL⁻¹ for THC and CBD, respectively. The recovery of the cannabinoids from the collection pad was greater than 80% for both cannabinoids tested at 2.5 μg mL⁻¹, and the inter-day precision was less than 6% for all analytes. The procedure was applied to oral fluid specimens after the controlled ad libitum smoking of one cannabis cigarette.