Chromatographic characterisation of 11 phytocannabinoids: Quantitative and fit-to-purpose performance as a function of extra-column variance.

INTRODUCTION: Cannabis sativa L. (cannabis) is utilised as a therapeutic and recreational drug. With the legalisation of cannabis in many countries and the anticipated regulation of potency that will accompany legalisation, analytical testing facilities will require a broadly applicable, quantitative, high throughput method to meet increased demand. Current analytical methods for the biologically active components of cannabis (phytocannabinoids) suffer from low throughput and/or an incomplete complement of relevant phytocannabinoids. OBJECTIVE: To develop a rapid, quantitative and broadly applicable liquid chromatography-tandem mass spectrometry analytical method for 11 phytocannabinoids in cannabis with acidic and neutral character. METHODOLOGY: Bulk diffusion coefficients were calculated using the Taylor-Aris open tubular method, with four reference compounds used to validate the experimental set-up. Three columns were quantitatively evaluated using van Deemter plots and fit-to-purpose performance metrics. Low (1.2 µL2 ) and standard (3.6 µL2 ) extra-column variance ultra-high pressure liquid chromatography (UPLC) configurations were contrasted. Method performance was demonstrated with methanolic cannabis flower extracts. RESULTS: Bulk diffusion coefficients and van Deemter plots for 11 phytocannabinoids are reported. The developed chromatographic method includes the challenging Δ8 /Δ9 -tetrahydrocannabinol isobars and, at 6.5 min, is faster than existing methods targeting similar panels of biologically active phytocannabinoids. CONCLUSIONS: The bulk diffusion coefficients and van Deemter curves informed the development of a rapid quantitative method and will facilitate potential expansion to include additional compounds, including synthetic cannabinoids. The developed method can be implemented with low or standard extra-column variance UPLC configurations.

Pushing the performance limits of reversed-phase ultra high performance liquid chromatography with 1.3µm core-shell particles.

Innovative columns made with very small core-shell particles (1.0-1.4µm) were investigated over a wide experimental space using state-of-the-art ultra high performance liquid chromatography (UHPLC) instruments. Among the columns tested is one that is now commercially available and is made with 1.3µm core-shell particles consisting of non-porous cores about 0.9µm in size and porous shells <0.2µm thick. This work demonstrated that exceptionally low observed minimum plate heights of 2.2µm could be obtained using columns packed with 1.3µm particles, corresponding to a plate count of over 450,000 plates/m. It was shown that only low volume columns allow operation under optimal conditions with current top-of-the-line UHPLC instruments. It was also demonstrated that the loss in performance caused by frictional heating effects remains negligible. Finally, the practical utility of these columns was confirmed with several real-world applications requiring extreme resolving power (i.e. peptide mapping, sample typical of metabolomic studies and crude human insulin). The performance achieved was compared to that of a reference UHPLC column packed with 1.7µm fully porous particles. The column packed with 1.3µm particles gave peak capacity values that were 20-40% higher than the reference column for the same analysis time.