Homogeneous liquid phase microextraction using hydrophilic media for the determination of fluoroquinolones in human urine using HPLC-FLD

Miniaturization of liquid-phase extraction is an increasingly emerging field of sample preparation aiming to reduce the solvent consumption and to protect the environment. In this paper, a homogeneous liquid phase microextraction using a hydrophilic extraction media in combination with a salt as phase-forming agent was developed for the determination of four fluoroquinolones (ciprofloxacin, norfloxacin, moxifloxacin and prulifloxacin) in human urine. Important parameters affecting the extraction performance including sample volume, organic solvent volume, salt concentration etc were systematically investigated and optimized. Multivariate experimental designs namely Plackett-Burman and Box-Behnken designs were sequentially applied for factor screening and optimization of the method parameters. The method was fully validated using the "total error" approach. Accuracy profiles - a graphical decision-making tool - were constructed using the results of the validation procedures. The beta-expectation tolerance intervals did not exceed the acceptance criteria of +/- 15%, meaning that 95% of future results will be included in the defined bias limits. The relative bias ranged between - 2.8 to 7.7 % for all analytes, while the RSD values for repeatability and intermediate precision were less 6.6%. The achieved limits of detection (LOD) were ranged between 3 and 11 ng mL(-1) while the lower limits of quantitation (LLOQ) were established as 10 ng mL(-1) for ciprofloxacin and norfloxacin and 100 ng mL(-1) for moxifloxacin and prulifloxacin, respectively. The ruggedness of the microextraction procedure was assessed through Monte-Carlo simulations and capability analysis. The proposed approach improves the procedures proposed to date for the bioanalysis of fluoroquinolones in terms of efficiency, reduction of the sample volume and extraction time.