PVC Membrane Selective Electrode for Determination of Cadmium(II) Ion in Chocolate Samples

Abstract

Benzil bis(carbohydrazone) (BBC) is prepared and explored as new N—N Schiff's base, which plays the role of an excellent ion carrier in the construction of a Cd(II) ion membrane sensor. The tris(2-ethylhexyl) phosphate best performance corresponds to a membrane composition of 30% poly (vinyl chloride), 65% (TEHP), 3.5% BBC and 1.5% tetradodecyl-ammoniumtetrakis(4-chlorophenyl) borate (ETH 500). This sensor shows very good selectivity and sensitivity towards cadmium ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The effect of membrane composition, selectivity, pH and influence of additive on the response properties of electrode were investigated. The response mechanism was discussed in the view of UV-spectroscopy. The electrode exhibits a Nernstian behavior (with slope of 29.7 mV per decade) over a very wide concentration range from 1.0×10−1 to 1.0×10−8 mol·L−1 with a detection limit of 3.2×10−8 mol·L−1. It shows relatively fast response time in whole concentration range (<8 s) and can be used for at least 10 weeks in the pH range of 2.0–9.0. The proposed sensor is successfully used for the determination of cadmium in different chocolate samples and as indicator electrode in titration with ethylene diamine tetraacetate (EDTA).