Development and Validation of an Analytical Method Based on HPLC-ELSD for the Simultaneous Determination of Rosmarinic Acid, Carnosol, Carnosic Acid, Oleanolic Acid and Ursolic Acid in Rosemary

The safety, efficacy and stability of natural antioxidants have been the focus of research in the food industry, with the aim of rapidly analyzing and controlling the quality of rosemary and its extracts, a novel analytical method involving high-performance liquid chromatography with evaporative light scattering detection (HPLC-ELSD) was developed for the simultaneous determination of rosmarinic acid, carnosol, carnosic acid, oleanolic acid and ursolic acid in rosemary. Chromatographic separation was conducted with gradient elution mode by using a Zorbax SB-C18 column (4.6 mm × 250 mm, 5 μm) with mobile phases of methanol and 0.6% acetic acid. The drift tube temperature of ELSD was 70 °C, and the pressure of nebulizer nitrogen gas was 40 Psi. The method developed has high sensitivity (with limits of detection from 1.3 to 8.6 μg/mL), acceptable linearity over the tested concentrations (with correlation coefficients from 0.991 to 0.999), good repeatability (with intra- and inter-day CV less than 3.1% for all analytes) and satisfactory accuracy (with recovery between 95.5% and 100.8%). The method has been demonstrated as a powerful tool for the functional ingredients analysis and quality control of rosemary and its extracts in a cost- and time-effective manner.