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Abstract The problem of water pollution is one of the most important problems that we face because of its harmful effects on public health and the environment. Studying some of these pollutants using new electrodes.The aim of this thesis were developed to the design of a novel electrode as were described consisting of pDAAQ/pDAN@GCE, pDAN/pDAAQ@GCE and molybdate/ pDAN/pDAAQ@GCE composite electrodes by electropolymerization method using CV. This developed composite electrodes were applied for improved simultaneous determination nitrite and phosphate ions. The thesis consists of three chapters as follows: Chapter one : This chapter focused on general background of modified electrodes, how to modify electrode surface electro-chemically and the conducting polymers with special focus on poly diaminonaphthalene and what makes polymers conductive? their synthesis by introducing highlights about both chemical and electrochemical polymerization and its applications. Also I paid a great attention to general description of nitrite “Identity, properties of nitrite, uses of nitrite and adverse effect of it in food and drinking water and different methods of detection nitrite” . Finally of this chapter I introduced a general background about phosphate general description of it, An important occurrence of phosphates in biological systems, geological occurrence and electrochemical Phosphate detection methods. Chapter two : This chapter reported the experimental part which mainly stated with electrochemical preparation of pDAAQ/pDAN@GCE and pDAN/ pDAAQ @GCE composite electrodes via CV at GCE using a 1.5x10-3M DAN solution in 1.0 M HClO4. Its activity was recorded in a CH3CN solution containing 0.1 M LiClO4 for 15 cycles at a potential range of 0.0–0.8 V and a scan rate of 0.02 V s−1 . Summary 73 Similarly, pDAAQ was synthesized via CV at GCE using a 0.1 M DAAQ monomer solution in 1.0 M HClO4, and its activity was recorded in 0.1 M LiClO4/CH3CN for 15 cycles in a potential range of 0.2–1.4 V at ʋ 0.5 V s−1. To produce the pDAAQ/pDAN@GCE and pDAN/pDAAQ@GCE composite electrodes, pDAAQ/pDAN and pDAN/pDAAQ were deposited layer by layer using the same procedure. Also reported about electrochemical preparation of Molybdate/ pDAN/pDAAQ@GCE composite electrode was prepared via CV method between of -0.5 and 0.5 V vs. Ag/ AgCl in 0. 1M [(NH4)6Mo7O24.4H2O] solution for 10 scanning cycles at a scan rate of 0.1 Vs-1 on the surface of pDAN/pDAAQ@GCE composite electrode and supporting electrolyte 0.1 M H2SO4,and also reported about preparation of real samples. Chapter three: Part I: This chapter disclosed the characterization of pDAAQ and pDAN were electrochemically deposited layer by layer on a GCE to generate pDAAQ/pDAN@GCE and pDAN/pDAAQ@GCE composite electrodes, respectively. The morphology and characteristics of the modified electrodes were investigated via EIS, FT-IR, and SEM. The obtained results reveal the outstanding performance of the pDAN/pDAAQ@GCE electrode for electrochemical nitrite sensing where pDAAQ plays a vital role as the inner layer. CV, LSV, and DPV measurements revealed that the oxidation peak current of nitrite was proportional to its concentration. Part II : The molybdate/ pDAN/pDAAQ@GCE underwent CV in a solution of 0.1M NaOH, and repetitive scanning was used to assess the formation of MoO4 2−, where the phosphomolybdate complex was formed under acidic conditions. Molybdate/ pDAN/pDAAQ@GCE composite electrode can use for electrochemical detection PO4 3- using LSV after determine the Summary 74 optimize conditions of analytical, Some factors that affect the oxidation behavior of phosphate ions have also been studied |