Optimization of temperature-controlled ionic liquid homogenous liquid phase microextraction followed by high performance liquid chromatography for analysis of diclofenac and mefenamic acid in urine sample

In this work, a temperature-controlled ionic liquid homogeneous liquid phase microextraction (TCIL-HLPME) technique followed by HPLC–UV was applied for preconcentration and determination of diclofenac (DIC) and mefenamic acid (MEF) in urine samples. 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) was used as the optimum extraction solvent. Experimental design and response surface methodology was used for the optimization process. Firstly, a screening step, using Plackett-Burman design, was carried out to find the significant factors on the extraction efficiency and subsequently, a central composite design (CCD) was employed to find the optimum values of these parameters. The optimal conditions were obtained as extraction solvent volume of 105 µL; sample pH of 2.0, extraction time of 6 min, centrifugation time of 5 min; heating time of 2 min; heating temperature of 50 °C and 20 % of NaCl. Under optimized conditions, the preconcentration factors of 82 and 60 were obtained for DIC and MEF, respectively. The detections limits of 20 and 30 ng mL−1 were achieved for DIC and MEF by the proposed method, respectively. The calibration curves were linear in the range of 40–1000 and 60–1000 ng mL−1 for DIC and MEF, respectively. The intra- and inter-assay precisions (RSD %, n = 3) were in the range of 3.5–4.4 % and 7.3–8.0 % at the concentration level of 100 ng mL−1, respectively. The validated method was successfully applied for the analysis of target analytes in some urine samples.