Separation of monoterpenes in orange essential oil by capillary liquid chromatography and micellar electrokinetic chromatography

This paper describes the evaluation of alternative techniques, for the determination of selected volatile compounds in cold-pressed orange oil. Two techniques were investigated: capillary-LC (C-LC) and micellar electrokinetic chromatography (MEKC). The separation by C-LC was performed on a 23 cm. x 0.53 mm i.d. fused-silica column packed in house with RP-18. Acetonitrile:water (80:20) was used as mobile phase. The compounds were detected at 195 and 240 nm in a UV-detector with either a Z or U shaped flow cell. In MEKC, 50 mM SDS was used in a 20 mM phosphate buffer at pH 8.1, and separations were carried out at 20 kV A fused-silica capillary (75 mum i.d., 52.5 cm effective length, 60 cm total length) was used. On-column UV detection was conducted at 214 and 254 nm. A clean-up with C-18 as adsorbent and acetonitrile as eluent was performed before the chromatographic and electrophoretic runs in order to remove the colored components that could promote interference in the analysis. Capillary-LC allowed the determination of terpenes such as mircene, limonene, alpha-pinene, and oxygenated terpenes including linalool, citral, and carvone while, in MEKC, carvone, mircene, linalool, limonene, and citral were determined.