Validated determination of losartan and valsartan in human plasma by stir bar sorptive extraction based on acrylate monolithic polymer, liquid chromatographic analysis and experimental design methodology.

In our previous work, a new monolithic coating based on vinylpyrrolidone-ethylene glycol dimethacrylate polymer was introduced for stir bar sorptive extraction. The formulation of the prepared vinylpyrrolidone-ethylene glycol dimethacrylate monolithic polymer was optimized and the satisfactory quality of prepared coated stir bar was demonstrated. In this work, the prepared stir bar was utilized in combination with ultrasound-assisted liquid desorption, followed by high-performance liquid chromatography with ultraviolet detection for the simultaneous determination of losartan (LOS) and valsartan (VAS) in human plasma samples. In a comparison study, the extraction efficiency of the prepared stir bar was accompanied much higher extraction efficiency than the two commercial stir bars (polydimethylsiloxand and polyacrylate) for both target compounds. In order to improve the desorption efficiency of LOS and VAS, the best values for effective parameters on desorption step were selected systematically. Also, the effective parameters on extraction step were optimized using a Box-Behnken design. Under the optimum conditions, the analytical performance of the proposed method displayed excellent linear dynamic ranges for LOS (24-1000 ng mL-1) and VAS (91-1000 ng mL-1), with correlation coefficients of 0.9998 and 0.9971 and detection limits of 7 and 27 ng mL-1, respectively. The intra- and inter-day recovery ranged from 98 to 117%, and the relative standard deviations were less than 8%. Finally, the proposed technique was successfully applied to the analysis of LOS and VAS at their therapeutic levels in volunteer patient plasma sample. The obtained results were confirmed using liquid chromatography-mass spectrometry. The proposed technique was more rapid than previously reported stir bar sorptive extraction techniques based on monolithic coatings, and exhibited lower detection limits in comparison with similar methods for the determination of LOS and VLS in biological fluids. The obtained results were demonstrated that the lower selectivity of UV in comparison with MS detection was rectified by appropriate sample preparation through proposed extraction method to eliminate as many interfering compounds as possible.