Assessing the separation of neutral plant secondary metabolites by micellar electrokinetic chromatography

In this work, partition coefficients (Pwm) and solute–micelle association constants per monomer (Km/N) were measured using micellar electrokinetic chromatography in tetraborate–sodium dodecylsulfate electrolytes for 18 important plant secondary metabolites (coumarin, verbenone, camphor, eucalyptol, carvone, α-terpineol, linalool, jasmone, bergapten, rose oxide, geraniol, t-anethole, citronellal, citronellol, p-cymene, limonene, caryophyllene and nerol) of wide occurrence in herbal extracts and essential oils. Caryophyllene presented a retention time longer than anthracene (micelle marker) and its set of constants could not be determined accurately. Pwm and Km/N were generated by the non-linear data fitting of both partition and solute–micelle association models for the 17 solutes under consideration (caryophyllene excluded). Pwm varied from 147 (coumarin) to 13 175 (limonene) while Km/N varied from 37 (coumarin) to 3721 (limonene). Under optimal conditions, the separation of the selected compounds was attempted successfully in commercialized samples of rose, anise and geranium essential oils.