Determination of phenazopyridine in biological fluids using electromembrane extraction followed by high-performance liquid chromatography

Recently, electro-assisted extraction of ionic drugs from biological fluids through a supported liquid membrane and into an aqueous acceptor solution was introduced as a new sample preparation technique and has been termed electromembrane extraction (EME). In the present work, this microextraction technique combined with high-performance liquid chromatography and ultraviolet detection has been developed for detection of phenazopyridine (PP) as a local analgesic drug in human plasma and urine samples. From a 6.5 mL neutral aqueous sample, PP was extracted for 20 min through a thin supported liquid membrane of 2-nitrophenyl octyl ether sustained in the pores of the wall of a porous hollow fiber and into an aqueous acidic acceptor solution (25 μL, containing negative electrode) by application of a DC electrical potential. The effects of several factors, including the nature of organic solvent, HCl concentration in donor and acceptor solutions, stirring speed, extraction time, and applied voltage on the extraction efficiency of the drug, were investigated and optimized. Satisfactory linearity ranges with correlation coefficients higher than 0.996 in different extraction media, admissible limits of detection (0.5 and 1.0 ng mL−1 in urine and plasma samples, respectively) and good repeatability and reproducibility (intra- and inter-assay precisions ranged between 3.7%–6.8% and 8.8%–12.5%, respectively) were obtained. The optimized EME procedure was applied to determine the concentration of PP in various matrices, such as plasma and urine samples, and satisfactory results were obtained.