Ultrasonic-Assisted Matrix Solid-Phase Dispersion and High-Performance Liquid Chromatography as an Improved Methodology for Determination of Oleuropein from Olive Leaves

In this study, ultrasonic-assisted matrix solid-phase dispersion (UA-MSPD) as a new sample preparation method for natural product analysis was developed. Influential parameters of the UA-MSPD method was optimized using oleuropein content of olive leaves as a model analyte. Main parameters of the proposed technique such as ultrasonic time, amplitude and pulse, sorbent material, the ratio of sample to sorbent material, elution solvent and its volume have been fully evaluated and optimized. In the proposed method several steps in classical MSPD including, transfer of sample and sorbent mixture to cartridge, packing and elution under vacuum conditions were removed. Also, ultrasound waves were applied to the sample and sorbent mixture in elution step for effective analyte desorption. Oleuropein was successfully extracted by silica gel and acetone as the sorbent and elution solvent, respectively. The calibration curve shows good linearity (R2=0.9979) and precision (RSD < 6.8) in the concentration range of 0.1-200 μg/mL for oleuropein. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.03 and 0.1 μg/mL, respectively. The recovery values were in the range of 90.2-96.7% with RSD values ranging from 5.5-7.2%.