Assay of terpene alcohols in pharmacopoeial essential oils by micellar electrokinetic capillary chromatography (MEKC).
Micellar electrokinetic capillary chromatography (MEKC) was used to separate and determine terpene alcohols of wide occurrence in herbal extracts and essential oils, namely eugenol, linalool, geraniol, citronellol and thymol. In the present paper sodium dodecyl sulfate (SDS) has been used as a micelle-forming additive to the CZE background electrolytes. Effects of SDS concentration, buffer type, its pH and concentration, addition of organic solvents on the migration times and separation efficiency were investigated. The optimal electrolyte system consisted of 20 mM TAPSO and 30 mM SDS in aqueous 10% (v/v) acetonitrile of pH 7.5 (adjusted by the addition of TRIS). The separation capillary was a fused silica tube (50 microm I. D., total length 75 cm, 42 cm effective length) maintained at 25 degrees C. The separations were performed at the applied voltage of 20 kV. Samples were injected hydrodynamically at a pressure of 50 mbar for 6 s. Detection was carried out at 200 nm. The calibration curves were rectilinear for 50-200 mg l(-1) (for eugenol, thymol and geraniol) and 100-400 mg l(-1) (for linalool and citronellol). The limits of detection varied between 5 mg l(-1) (for thymol) and 16 mg l(-1) (for linalool). The devised MEKC method was employed for the determination of the cited terpene alcohols as major quality-affecting constituents in commercial pharmacopoeial essential oils such as Geranii etheroleum, Caryophylli floris etheroleum, Lavandulae etheroleum and Thymi etheroleum. The results agreed well with those of a reference gas chromatographic method.
Petriska
I
I
Department of Analytical Chemistry, Faculty of Pharmacy, Charles University, Hradec Králové, Czech Republic.
Polásek
M
M
Sladkovský
R
R
D000438:Alcohols / Q000032:analysis*; D002138:Calibration; D002849:Chromatography, Gas; D020374:Chromatography, Micellar Electrokinetic Capillary; D009822:Oils, Volatile / Q000032:analysis*; D010602:Pharmacopoeias as Topic; D010944:Plants / Q000737:chemistry; D012015:Reference Standards; D015203:Reproducibility of Results; D013729:Terpenes / Q000032:analysis*
D000438:Alcohols; D009822:Oils, Volatile; D013729:Terpenes