Manufacturing of selective electrode using modified graphite paste to determine cadmium ion in aqueous solution and studing its potential properties

This study deals with manufacturing of electrochemical sensor (electrode) to determine cadmium (II) in aqueous solution using a (3-(4-nitro phenyl azo)-pentane-2,4-dion (LP)) dye complex with cadmium ions as electrochemical effective substance by mix it with graphite powder using paraffin oil as plasticizer. LP dye was prepared and its properties were studied. The identity of the complex with Cd2+ was confirmed using the spectroscopy methods in the ultraviolet (UV) and infrared (IR) range. The optimal components of the graphite paste were studied to choose the best composition, in addition to potentiometric study of the mixing ratio between the graphite powder and the active substance in the studied ion concentration range (1×10-3-1×10-7)M and the relation between the mixing ratio and the linear slope and slope corresponding to each ratio (30:70%) and (40:60)% (an effective substance: graphite) characterized by a very good Nernstic response on a wide range of concentrations with a slope of 28 and 31 respectively. the effect of pH value on the respond time of the manufactured electrode was studied. The result showed stability of the potential in pH range (3. 5 – 7) at a response time of 30-40 sec. The potential selectivity coefficients of the proposed electrode were calculated using the Matched Potential Method (MPM). The proposed electrode was used successfully as an detector electrode in the potentiometric calibration of the cadmium nitrate solution with disodium salt solution of EDTA.