Ion-pair vortex assisted liquid-liquid microextraction with back extraction coupled with high performance liquid chromatography-UV for the determination of metformin in plasma

摘要

A new sample preparation method, ion-pair vortex assisted liquid-liquid microextraction (VALLME-BE), for the determination of a highly polar anti-diabetic drug (metformin) in plasma sample was developed. The VALLME-BE was performed by diluting the plasma in borate buffer and extracted to 150 mu L 1-octanol containing 0.2 M di-(2-ethylhexyl)phosphoric acid as intermediate phase. The drug was next back-extracted into 20 mu L of 0.075 M HCl solution. The effects of pH, ion-pair concentration, type of organic solvent, volume of extraction phases, ionic strength, vortexing and centrifugation times on the extraction efficiency were investigated. The optimum conditions were at pH 9.3, 60 s vortexing and 2 min centrifugation. The microextract, contained metformin and buformin (internal standard), was directly injected into a HPLC unit using Cl column (250 mm x 4.6 mm x 10 jun) and detected at 235 nm. The method was validated and calibration curve was linear with r(2) > 0.99 over the range of 20-2000 mu g L-1. The limits of detection and quantitation were 1.4 and 4.1 mu g L-1, respectively. The accuracy was within 94.8-108% of the nominal concentration. The relative standard deviation for inter- and intra-day precision was less than 10.8%. The method was conveniently applied for the determination of metformin in plasma samples. (C) 2016 Elsevier B.V. All rights reserved.