Fast analysis of phenolic terpenes by high-performance liquid chromatography using a fused-core column†
A fused-core column was used to develop a fast and efficient analytical method for separating phenolic terpenes by high-performance liquid chromatography. The main chromatographic parameters, such as the composition of the mobile phase (mixtures of water and acetonitrile), the flow rate of the mobile phase (1.0–2.5 mL min−1), the column temperature (30–55 °C) and re-equilibration time after each injection (1–5 min) were studied and optimized during the development of the method. Using the current method, the major nonvolatile compounds from rosemary [rosmarinic acid (RA), rosmanol (RO), carnosol (CN), carnosic acid (CA) and methyl carnosate (MC)] could be separated in 4.7 min. The total time of analysis was 10 min, including the column cleanup and the re-equilibration period. The effect of the sample solvent was also studied. The combined influence of the injection volume and sample dilution on the performance of the chromatographic method was evaluated. The method was validated with several commercial samples, enabling the detection of low amounts (0.25 μg mL−1) of CA and RA. The chromatographic profile showed excellent repeatability (intraday) and reproducibility (interday). Furthermore, the peak separation was good when using ethanol for sample dilution with respect to resolution (2.1, 3.7, 6.4, 10.6 and 21.7 for RO, MC, RA, CA and CN, respectively), selectivity (1.0 for MC; 1.1 for RO and CA; 1.3 for CN; and 1.5 for RA) and peak symmetry (1.0 for RA, CN and MC; 1.1 for CA; and 1.2 for RO).