Switchable-hydrophilicity solvent liquid-liquid microextraction of non-steroidal anti-inflammatory drugs from biological fluids prior to HPLC-DAD determination.

Switchable-hydrophilicity solvent liquid-liquid microextraction was used prior to high-performance liquid chromatography with diode-array detector (HPLC-DAD) for the determination of four non-steroidal anti-inflammatory drugs [i.e., ketoprofen, etodolac, flurbiprofen and ibuprofen] in human urine, saliva and milk. Optimum extraction conditions were as follows: 500 μL switched-on N,N-dimethylcyclohexylamine as the extraction solvent, 9.5 mL of the aqueous phase, 500 μL 20 M sodium hydroxide as a switching-off trigger, and within 30 s extraction time. A portion of the final extract was directly injected into HPLC. Under optimized extraction and chromatographic conditions, limits of detection ranged between 0.04 and 0.18 μg mL ^-1 in all matrices analyzed. Good linearity with coefficients of determination (R ² ) ranging between 0.9955 and 0.9998, and percentage relative standard deviations (%RSD) of 0.9-7.7% were obtained. The proposed method was efficiently used for the extraction of the analytes in the biological fluids with percentage relative recoveries (%RR) ranging between 95.7 and 109.2%.
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