251ELECTROCHEMICAL DETERMINATION OF CIPROFLOXACIN HYDROCHLORIDE IN PHARMACEUTICAL FORMULATION, AQUATIC ENVIRONMENT AND IN FISH TISSUESTwo ciprofloxacin hydrochloride (CPX) selective electrodes were developed using dioctyl phthalate (DOP) as a plasticizer in a polymeric matrix of polyvinyl chloride (PVC). Sensor I was fabricated using tetrakis(4-chlorophenyl)borate (TpClPB) as an anionic exchanger without incorporation of an ionophore. Sensor II was developed using 2-hydroxy propyl β- cyclodextrin as an ionophore. Linear responses of CPX within a concentration range of 10-5-10-2 M, with slopes of 51.7 ± 0.31 and 48.7 ± 0.40 mV/ decade over pH range of 4-7 were obtained using sensors I and II, respectively. The selectivity coefficients of the developed sensors indicated excellent selectivity for CPX. The proposed method displayed useful analytical characteristics for determination of ciprofloxacin hydrochloride in pharmaceutical formulation , fish water and fish tissues with average recoveries of 100.91 ± 0.47, 96.42 ± 1.34 and 86.46 ± 1.28 , respectively for sensor I and 101.2 ± 0.37 , 97.26± 1.56 and 86.67± 1.70 , respectively for sensor IIh.marzouk@yahoo.comResearch462013Aquatic environment,Ciprofloxacin hydrochloride,Fish tissues,Potentiometry,PVCMamdouh R. Rezk,Safaa M. Riad,Fatma I. Khattab, Hoda M. MarzoukAnalytical Chemistry Department, Faculty of Pharmacy, Cairo University, Kasr El-Aini St., 11562, Cairo, Egypt.,Analytical Chemistry Department, Faculty of Pharmacy, Cairo University, Kasr El-Aini St., 11562, Cairo, Egypt.,Analytical Chemistry Department, Faculty of Pharmacy, Cairo University, Kasr El-Aini St., 11562, Cairo, Egypt.,Analytical Chemistry Department, Faculty of Pharmacy, Cairo University, Kasr El-Aini St., 11562, Cairo, Egypt.