Original articleA comparative study of liquid and solid inner contact roxatidineacetate ion-selective electrode membranesMohamed K. Abd El-Rahmana, Hala E. Zaazaaa,*, Samah S. Abbasa, Badr El-Zeanya,Zeinab A. EL-Sherifb, Dalia A. EL-HaddadbaAnalytical Chemistry Department, Faculty of Pharmacy, Cairo University, Kasr El-Aini Street, Cairo 11562, EgyptbNational Organization for Drug Control and Research, 6 Hussen Kamal El Deen, Ben-el-sariat, Dokki, Giza 12311, Egypt1. IntroductionRoxatidine (ROX), 2-(acetyloxy)-N-3-3-(1-piperidinyl meth-yl) phenoxy propyl acetamide is histamine H2-receptor antago-nist which also and has anti-ulcerative activity 1. Orallyadministered roxatidine acetate is rapidly metabolized to anactive metabolite roxatidine, by esterases in the small intestine,liver and plasma 2,3.Different chromatographic techniques were applied for thedetection and determination of ROX in biological fluids. Thesetechniques include high performance liquid chromatography(HPLC) with UV detector 4, liquid chromatographymass spec-trometry (LCMS) 5,6, gas chromatographymass spectrometry(GCMS) 7, and capillary gas chromatography with nitrogenselective detection 8. Also, ROX was determined in pharmaceu-ticals by spectrophotometry 9 and capillary zone electrophoresis(CZE) 10. Recently, our work on roxatidine stability by chro-matographic methods has been published 11.Since, some of these methods suffer from either wide spreadavailability of instrumentation, prohibitive cost or technicaldifficulty. potentiometric membrane sensors have been moreextensively used in pharmaceutical analysis over the last twodecades. This technique offers significant promise as an analyticaltool in pharmaceutical quality control and coupled with thereliability of the analytical information, leads to attractiveapproach for the assay of pharmaceutical products. Careful reviewof the literature found no solid or liquid inner contact ion-selectiveelectrode membranes for determination of ROX.Design of sensors with improved characteristics of a certainchemical species is quite challenging in chemical research. To thisend, we are undertaking this work that involves the design, studyChinese Chemical Letters 26 (2015) 714720A R T I C L E I N F OArticle history:Received 17 September 2014Received in revised form 13 November 2014Accepted 15 December 2014Available online 19 March 2015Keywords:Comparative studyRoxatidine acetateLiquid inner contact electrodeSolid contact electrodeDegradation productPlasmaA B S T R A C TA comparative study was conducted using two designs of a roxatidine acetate (ROX)-selective electrode;a conventional liquid inner contact called electrode A and a graphite-coated solid contact calledelectrode B. The fabrication of electrodes was based on roxatidine-tetraphenylborate (ROX-TPB) as anion-association complex in a PVC matrix using different plasticizers. Electrode A has a linear dynamicrange of 2.2 ? 10?5mol/L to 1.0 ? 10?2mol/L, with a Nernstian slope of 54.7 mV/decade and a detectionlimit of 1.4 ? 10?6mol/L. Electrode B shows linearity over the concentration range of 1.0 ? 10?6mol/L to1.0 ? 10?2mol/L, with a Nernstian slope of 51.2 mV/decade and a limit of detection of 1.1 ? 10?7mol/Lwhich is remarkably improved as a result of diminishing ion fluxes in this solid contact, ion-selectiveelectrode. The proposed sensors display useful analytical characteristics for the determination of ROX inbulk powder and its pharmaceutical formulation. The present electrodes show clear discrimination ofROX from several inorganic, organic ions, sugars, some common drug excipients and the degradationproduct (3-3-(1-piperidinyl methyl) phenoxy propyl amine) of ROX. Furthermore, the proposedelectrodes were utilized for the determination of ROX in human plasma, where electrode B covers drugCmaxwhich indicated its applicability to pharmacokinetic, bioavailability and bioequivalent studies. Theresults obtained by the proposed electrodes were statistically analyzed and compared with thoseobtained by a reported HPLC method. No significant difference for either accuracy or precision wasobserved.? 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.Published by Elsevier B.V. All rights reserved.* Corresponding author.E-mail addresses: , hala.zaazaapharma.cu.edu.eg(H.E. Zaazaa).Contents lists available at ScienceDirectChinese Chemical Lettersjo u rn al h om epag e: ww w.els evier.c o m/lo cat e/cc lethttp:/dx.doi.org/10.1016/j.cclet.2015.03.0101001-8417/? 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.and comparison of new electrodes to determine ROX ions insolution. The construction of a polymeric membrane, ion-selectiveelectrode traditionally required a relatively high concentration ofthe ion of interest in the inner filling solution (IFS); however,experimental evidence suggested that this has a deteriorati