Usefulness of the chaotropic effect in sample preparation for chromatographic analysis of acidic xenobiotics in human plasma

Abstract

In this study a new RP-HPLC with photo-diode array detection method for the determination of ibuprofen ((RS)-2-(4-isobutylphenyl)propionic acid) in human plasma samples was developed. Samples were prepared by SPE and analyzed by an isocratic elution mode over a C18 column using 80% methanol. A novel sample pretreatment method, based on the addition of ionic liquids possessing chaotropic ions to small human plasma sample (100 μL), was elaborated. 1-Butyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM BF4 ) were tested from the point of view of extraction yield. Quantification was based on calibration curve applying diclofenac as the internal standard. Owing to dilution of plasma sample by 2 mM aqueous solution of BMIM BF4 before SPE, appropriate sample purification and extraction yields higher than 95% with precision lower than 2% can be achieved. Linear coefficients of correlation (r(2)) were >0.99 in the range of 0.3-5 μg/mL ibuprofen concentration in plasma. The limit of quantification was 65 ng/mL and the detection limit for ibuprofen was 19.5 ng/mL.

Keywords: Chaotropic effect; Human plasma; Ibuprofen; Ionic liquids.