Testing cannabis products for potency is typically performed by LC-UV/VIS. This methodology is robust, reliable, and cost-effective but it has limited capabilities, namely, the complete chromatographic separation of all compounds and reduced detection sensitivity compared to MS. As cannabis research continues to accelerate, it is likely new phytocannabinoids of interest will need to be added into potency testing methods, which can be challenging due to the limited chromatographic space. MS can offer a sensitive and selective alternative to LC-UV/VIS methods by reaching much lower detection limits while only requiring the separation of isobaric compounds. In this work, a method was developed to detect 21 cannabinoids by LC-MS using isocratic mobile phase conditions. The method was performed on an LC-MS using electrospray ionization in positive and negative ion modes. Complete resolution of isobars was achieved using isocratic mobile phase (MP) conditions at 20:80 (MPA:MPB) with mobile phases containing 0.1% formic acid and 12 mM ammonium formate in water (A) and 0.1% formic acid in acetonitrile:methanol (50:50) (B). The column used for these experiments was a Raptor ARC-18 150 mm x 2.1 mm, 2.7 µm with the column oven at a temperature of 30 °C and a flow rate of 0.5 mL/min. In these experiments, 21 cannabinoids were monitored, including two recently discovered compounds, tetrahydrocannabiphorol (THCP) and cannabidiphorol (CBDP). Compounds indistinguishable by MS were identified and isolated to five groups. Chromatographic separation was essential within these five groups of isobars, which was achieved using the outlined conditions.
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