RESOLUTION OF CHIRAL CANNABINOIDS ON AMYLOSE TRIS(3,5-DIMETHYLPHENYLCARBAMATE) CHIRAL STATIONARY-PHASE - EFFECTS OF STRUCTURAL FEATURES ANDMOBILE-PHASE ADDITIVES

The separation of six pairs of chiral cannabinoids was achieved using a dimethylphenylcarbamate derivative of amylose, immobilized on silica gel (ChiralPak AD, Daicel), using 2-propanol and ethanol as the modif iers of n-hexane in the mobile phase. Good separation was achieved for most of the solutes in both solvent systems under various conditions. The chromatographic parameters of various cannabinoids in the two sol vent systems were determined. The pairs differ from each other in smal l structural features such as the degree of saturation, position of a double bond and closure of a pyran ring. Therefore, a comparative stud y could give some dues regarding the mechanism of discrimination betwe en the enantiomeric pairs on the chiral stationary phase. Preliminary measurements of limit of determination showed that it was possible to assess 99.9% enantiomeric purity of the cannabinoids, owing to the hig h efficiency of the separation. Enantiomers of two monoterpenes, used as intermediates or as starting materials in the chiral synthesis of c annabinoids, were also separated, hence the described procedure is cap able of assessing whether the chiral centres in the molecules were sus tained throughout the synthetic procedures.