Cloud point extraction-HPLC method for determination and pharmacokinetic study of flurbiprofen in rat plasma after oral and transdermal administration

A method based on cloud-point extraction (CPE) was developed for the determination of flurbiprofen (FP) in rat plasma after oral and transdermal administration by high-performance liquid chromatography coupled with UV detection (HPLC–UV). The non-ionic surfactant Genapol X-080 was chosen as the extract solvent. Variables parameter affecting the CPE efficiency were evaluated and optimized. Chromatography separation was performed on a Diamond C18 column (4.6 mm i.d. × 250 mm, 10 μm particle size) by isocratic elution with UV detection at 254 nm. The assay was linear over the range of 0.2–50 and 0.1–10 μg/ml for oral and transdermal administration, respectively, and the lower limit of quantification (LLOQ) was 0.1 μg/ml. The extraction recoveries were more than 84.5%, the accuracies were within ±3.8%, and the intra- and inter-day precisions were less than 10.1% in all cases. After strict validation, the method indicated good performance in terms of reproducibility, specificity, linearity, precision and accuracy, and it was successfully applied to the pharmacokinetic study of flurbiprofen in rats after oral and transdermal administration.