Design and Application of a Triiodide‐Selective Membrane Electrode

Abstract

I 3À -selective electrodes with a PVC membrane containing ionic associates of crystal violet (CV) triiodide as electrode-active substance were developed. The pH working range is 2-12, the linearity range of the electrode function is 9 10 À6 -1 10 À1 mol/L, and the electrode function slopes are varying from 44.0 to 62.0 mV/decade, depending on the plasticizers in the membranes. The efficiency of the use of these electrodes for dibenzoyl peroxide and magnesium monoperoxyphthalate determination in pharmaceutical preparations was shown by potentiometric titration methods. Due to the functional properties of ion associates (IA) to donate both a cation and an anion as potential-determining ions, they are the most universal ionophores [2][3][4][5]. It is likely that solubility is the main restriction for their use as ionophores [5]. The solubility of IAs should be sufficiently low in water phase; otherwise they will be washed out from the membranes, and, at the same time, large in the membrane phase, because it will be difficult to obtain a homogeneous membrane. Ion associates formed by various quaternary ammonium or phosphonium bases most often exhibit such properties [2][3][4][5][6][7][8][9][10][11][12]. Previously, we analyzed the applicability of ISEs based on ion associates of basic dyes as electrode active substances in analytical chemistry [13][14][15][16]. These systems were barely used for the determination of organic substances. KeywordsThe iodide ion is a sufficiently good reducing agent to react quantitatively with a number of oxidizing agents. It has various applications in industry, pharmacology, food and environmental pollution, such as determination of iron, copper and antimony in ore [17] We previously demonstrated the effectiveness of IA on the basis of crystal violet for making diclofenac selective sensors [32].In this work, we report on the use of crystal violet (CV) triiodide ion associate as an excellent ionophore for a PVC membrane triiodide sensor, and develop a simple and inexpensive technique for the assaying of dibenzoyl peroxide and magnesium monoperoxyphthalate in pharmaceutical preparations by potentiometric titration methods.An ion associate of triiodide and crystal violet was prepared by mixing equal quantities of 1 10 À2 mol/L triiodide solution and 1 10 À2 mol/L basic dye CV solution. The mixture was settled during 2 hours and the sediment of the ion associate was filtered (quantitative rapid filter paper). This residue was treated with 50 mL cold distilled water. The filter paper containing the precipitate was dried for 24 h at room temperature. This triiodide-CV IA was used as an electrode active substance (EAS) for preparing ISEs for magnesium monoperoxyphthalate determination.A triiodide-selective electrode for ionometric analysis was developed using PVC membranes plasticized with dibutyl phthalate (DBP), dioctyl phthalate (DOP), dinonyl phthalate (DNP), dibutyl sebacate (DBS), or tricresyl 2144