Abstract
In this work a new sensor was established for the direct determination of the important anions sulphite and nitrite. The sensor consisting of carbon paste modified with stannic-hexacyanoferrate immobilized in a tube of Teflon or plastic syringe. Paraffin wax was used as a binder to increase the stability, handling, and enhancing the mechanical properties of the paste. The capability of sensor for determination of sulfites and nitrites was evaluated by cyclic voltammetry and differential pulse voltammetry, the later technique has provided the sensor with the sensitivity needed the reproducibility and the repeatability. The sensor was used in both oxidation and reduction directions and in a wide range of pH values according to the analyte of interest. A linear relationship between peak current and concentration of the studied anions in the range of 7.5 μM to 5 mM for nitrite and 27 M-5 μM for sulfite, with correlation coefficient of 0.993 and 0.999 for sulfite and nitrite respectively. The active surface area of the electrode can be renewed easily by slightly polishing on fine sand paper.
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