Anal. Bioanal. Electrochem., Vol. 7, No. 1, 2015, 75-90 Full Paper Development of Membrane Electrodes for the Specific Determination of Tetryzoline Hydrochloride in Presence of its Degradation Product in Pharmaceutical Formulations and Biological Fluids Nagiba Y. Hassan 1 , Hayam M. Lotfy 1,2 , Sarah S. Saleh 3,* and Hesham Salem 4 1 Analytical Chemistry Department, Faculty of Pharmacy, Cairo University, Kasr-El Aini Street, 11562 Cairo, Egypt 2 Analytical Chemistry Department, Faculty of Pharmacy, Future University (FUE), 11835 New Cairo, Egypt 3 Analytical Chemistry Department, Faculty of Pharmacy, October University for Modern Sciences and Arts (MSA), 11787 6 th October City, Egypt 4 Analytical Chemistry Department, Faculty of Pharmacy, Deraya University, Minia, Egypt * Corresponding Author, Mobile: +201006095963 E-Mail: drsarahsalah@gmail.com Received: 11 October 2014 /Accepted: 6 February 2015/Published online: 28 February 2015 Abstract- Membrane selective electrodes were used to determine tetryzoline hydrochloride (TZH) in pure form, pharmaceutical preparations and in biological fluids. The membrane selective electrodes include construction of water insoluble ion-association complexes. The TZH ion exchangers were formed using tetraphenyl borate (TZH-TPB), phosphomolybdic acid (TZH-PMA) and phosphotungstic acid (TZH-PTA), in a plasticized PVC (polyvinyl chloride) matrix, using dibutyl phthalate (DBP) or dioctylphthalate (DOP) as a plasticizer. The performance characteristics of the developed sensors were evaluated according to IUPAC recommendations. The developed sensors showed good responses but the best electrochemical characteristics and selectivity coefficients were achieved with TZH-TPB sensor using DBP as a plasticizer, where the linear responses of TZH was found within the concentration ranges of 10 −6 to 10 −2 mol/L and Nernstian slope was calculated to be of 56.8 mV/ decade at 25 °C, over the pH range of 5–9. The suggested method was used to determine TZH in synthetic mixtures, pharmaceutical formulations and in presence of its alkali degradation product. The proposed sensors displayed useful analytical characteristics for the determination of TZH in biological fluids such as rabbit aqueous humor and human plasma. The later application can be used to detect oral TZH poisoning in children. The obtained Analytical & Bioanalytical Electrochemistry 2015 by CEE www.abechem.com