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.