Improvement for the LC-MS/MS determination of Δ⁹-tetrahydrocannabinol (THC) in cannabidiol (CBD) isolate powder: application of normal phase chromatographic preparation

Abstract

A regulatory limit has been established in Japan for the total concentration of Δ⁹-tetrahydrocannabinol (Δ⁹-THC) and Δ⁹- tetrahydrocannabinolic acid (Δ⁹-THCA), in cannabidiol (CBD) products. For CBD isolate powder, a raw material, a strict limit of 10 ppm is set for total Δ⁹-THC levels. However, due to the reported monitoring ions shared by CBD and Δ⁹-THC on LC-MS/MS analysis, conventional dilution-based methods suffer from significant signal interference, which makes accurate quantification of Δ⁹- THC in high-CBD-content matrices. In this study, we developed the normal-phase liquid chromatographic (DCpak^® P4VP column) preparation for an LC-MS/MS method to accurately quantify trace levels of Δ⁹-THC in CBD isolate powder. This sample preparation was validated based on spike-and-recovery tests (repeatability and intermediate precision) at three concentration levels (1, 5, and 10 μg/g in sample) which demonstrated excellent accuracy (94.3%–108.9%) and RSD (≤3.6%) using internal standard curves with Δ⁹- THC-d₃, respectively. This improved method enables reliable quantification of at regulatory levels in high-CBD products such as isolates and others in compliance with the Japanese guidelines for analytical method validation of food additives.