Microextraction in a packed syringe for the analysis of olive biophenols in rat plasma using CMK-3 nanoporous sorbent

A carbon-based nanoporous sorbent was first used for microextraction in a packed syringe (MEPS) before HPLC/UV analysis of some biophenols in rat plasma. A laboratory-made programmable apparatus was designed and used for automation of the extraction procedure. The MEPS syringe was packed with 2 mg of CMK-3 sorbent, between the barrel and the injection needle, and mounted on an apparatus for programming of the conditioning, sampling, washing, elution and cleaning steps. All steps of the microextraction procedure were carefully optimized on the system. For optimization of important factors, such as the number of adsorption and elution cycles, elution volume and pH, a multivariate central composite design method was used. The highest recoveries were obtained for 24 and 10 times of adsorption and elution cycles, respectively, using 100 μL of acetonitrile as the eluent and a sample pH of 2. Good results were obtained in terms of the precision (RSD 1.6, 2.5 and 2.3%) and detection limit (0.7, 4.7 and 0.25 μM) for caffeic acid, tyrsol and oleuropein, respectively. The method was simple, efficient and appropriate for sample clean up before analysis by HPLC, and was successfully applied to the determination of biophenols in the plasma of several rats that received an olive leaves extract either by a gavage or an intraperitoneal injection method. A positive correlation was found between the amount of olive extract's feeding of the rats and the level of their plasma biophenols.