DETERMINATION OF PIRETANIDE AND FUROSEMIDE IN PHARMACEUTICALS AND HUMAN URINE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH AMPEROMETRIC DETECTION

A high-performance liquid chromatographic method with electrochemical detection (ED) has been developed for the determination of two diureti cs: 4-phenoxy-3-(1-pyrrolidinyl)-5-sulfamoylbenzoic acid (piretanide) and 4-chloro-2-furfurylamino-5-sulfamoylbenzoic acid (furosemide). The chromatographic separation was performed on a mu Bondapak C-18 column with a mobile phase of acetonitrile-water (40:60) containing 5 mM KH2 PO4/K2HPO4 and with a flow-rate of 1 ml/min (69 bar). The temperature was optimized at 30 +/- 0.2 degrees C. The amperometric detector equip ped with a glassy carbon electrode was operated at + 1200 mV versus Ag /AgCl in the direct current mode. The method was applied to the determ ination of these compounds in two concentration ranges (ppm and ppb), obtaining a reproducibility in terms of relative standard deviations l ower than 1% for within-day and 4% for day-to-day and determination li mits of 15 ppb for both compounds. Recoveries greater than 90% were ob tained for spiked urine samples, using a liquid-liquid extraction meth od in the sample clean-up procedure. The LC-ED method was applied to c ommercially available pharmaceuticals (Seguril, furosemide 40 mg, and Perbilen, piretanide 6 mg) and urine samples obtained from healthy vol unteers and hypertensive patients.