A High-Sensitivity Potentiometric Mercuric Ion Sensor Based on m-Toluidine Films

A sensor of $m$ -toluidine polymer film coated platinum electrode was fabricated by the electropolymerization using cyclic voltammetry technique for the detection of mercury ions (Hg²⁺) in aqueous solution. This paper was carried out using the simple potentiometric method and confirmed by a cyclic voltammetry technique. The effects of the polymer film thickness and pH of Hg²⁺ solutions on the response of the sensor were studied. Moreover, the stability, sensitivity, and selectivity of the $m$ -toluidine sensor were investigated. The optimum thickness of the polymer film was obtained after ten cyclic voltammetric runs. This film has a Nernstian response slope of 29.19 mV/decade with a detection limit of $3.54\times 10^{\mathrm {\mathbf {-5}}}$ M at 293 K by the simple potentiometric method. In addition, it has a sensitivity of $4\times 10^{\mathrm {\mathbf {-7}}}$ AM $^{\mathrm {\mathbf {-1}}}$ with a detection limit of $1.33\times 10^{\mathrm {\mathbf {-7}}}$ M by the cyclic voltammetry method. Moreover, the sensor is specific to Hg²⁺ ions in the presence of other ions, such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Co²⁺, Ni²⁺, Zn²⁺, and Pb²⁺. Furthermore, the most stable response of the sensor to Hg²⁺ ions in the solution of pH ranged from 4 to 6.4 for a lifetime of about eleven weeks. Moreover, the sensor was applied for detection of four natural samples: 1) tap water; 2) underground water; 3) first distillate water; and 4) another sample wasted with Hg²⁺ ions.

I. Introduction

Environmental monitoring of the heavy metals is important because of the growing environmental problems [1]. Some of the heavy metals are dangerous to the environment such as mercury and cadmium. Some may cause corrosion such as zinc and lead, and some are harmful such as arsenic may pollute catalysts. Heavy metals pollutions are one of the main reasons for human illnesses such as the illness of vital organs, including liver and kidney that occur due to mercury and other metals toxicity [2], [3].