Three-Phase Solvent Bar Microextraction Combined with HPLC for Extraction and Determination of Plasma Protein Binding of Bisoprolol

Abstract

A three-phase solvent bar microextraction (TPSBME) technique combined with high performance liquid chromatography (HPLC)–fluorescence detection was evaluated for the quantitative determination of plasma protein binding of bisoprolol. Bisoprolol was extracted from a 5.6-mL basified plasma sample (donor phase) into the organic solvent (n-octanol) impregnated in the pores of a hollow fiber and then extracted into an acidic solution (acceptor phase) inside the lumen of the hollow fiber. Metoprolol was used as the internal standard. Several parameters influencing the efficiency of the method were investigated and optimized including organic solvent (n-butanol, n-octanol, dibutyl phthalate, dihexyl ether), stirring rate (100–1,000 rpm), extraction time (5–35 min), extraction temperature (15–45 °C), concentration of the donor phase (0.1–2 M NaOH) and the acceptor phase (0.5–5 M formic acid), salt concentration (2.5–10%, w/v). Under the optimal condition, extraction recoveries from plasma samples were above 61.4% for bisoprolol. The calibration curves were obtained in the range of 10–100 ng mL⁻¹ with reasonable linearity (r > 0.994). The method was successfully applied to determine the plasma protein binding rate of bisoprolol.