The synthesized rGO/ZrHCF modified electrode was characterized by UV-Vis spectra. Fig. shows the UV-Vis absorption spectra rGO/ZrHCF, wherein the absorption peak appearing at 215 and 245nm corresponds to the zirconium dioxide in the sample.
The peak around 320 and 387 nm was corresponds to reduced grapheme oxide.Freshly prepared rGO/PIG electrode were modified by potential scanning in a prepared zirconium hexacyanoferrate solution, at 100 mV-1 with the 40 succesive redox cycling experiments from -0.2 to 0.8 V were investigated which shown in fig. The effect of pH on the electro catalytic oxidation of sodium nitrite by rGO/ /ZrHCF modified electrode in different pH condition (3.
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0-8.0) has been studied. Fig. shows the cyclic voltammogram of sodium nitrite oxidation in different pH environment.
The maximum peak current was obtained at pH-5.0. Hence pH-5.
0 was considered as optimum for further determination of sodium nitrite. The inserted fig (a) shows the calibration plot of pH vs current for sodium nitrite oxidation. The result clearly shows the peak current increases until pH-5.0 and the gradually decreased.
This clearly shows the ABS pH -5.0 shows good current response The Cyclic voltammetry of sodium nitrite at the rGO/ZrHCF modified electrode were investigated at different scan rates are shown in Fig. By increasing the scan rate from 20 mVs-1 to 160 mVs-1, the oxidation and reduction peak currents of sodium nitrite is increases linearly. The peak potential for nitrite oxidation shifted positively and the reduction peak potential shifted negatively. The linear response of the anodic and cathodic peak currents versus scan rate has been presented in the fig. (a) and (b), both the peak current Ipa and Ipc shows good linear response with the corresponding co-relation coefficient R2 = 0.9940 and 0.
9960. The electrocatalytic oxidation of sodium nitrite has been studied in square wave voltammetry. The Fig.
shows the SWV determination for different concentration of sodium nitrite. By increasing the concentration of analyte there is an enhancement of oxidation current. The Fig. shows the calibration plot for the rGO/ZrHCF modified electrode modified electrode for the concentration of sodium nitrite vs. current, which gives a linear response towards sodium nitrite with good correlation coefficients of 0.990.
The SWV curves presented a oxidation potentials around 0.05 V for sodium nitrite. The obtained linear range for the sodium nitrite determination was 11.4 to 148.9 µM with limit of detection of 3.82 µM.
The stability as well as reproducibility of rGO/ZrHCF modified electrode was investigated by SWV measurements of 20.0 µM nitrite. By preserving the electrode, the customized electrode keeps about 97% of its initial response after two week and 92.7% after 45 days.
Therefore the electrode showed good stability and reproducibility over a period of 45 days. In order to evaluate the effect of interfering species on the electrocatalytic oxidation of sodium nitrite using the rGO/ZrHCF modified electrode, various analytes were selected, and the results are shown in (fig.) The optimized experiment with the modified electrode was repeated in the presence of 20 µM nitrite and varying the concentration of possible interferents (10 folds excess) like glucose, fructose, lactose and sucrose, which show minimal interference in the determination of nitrite using the modified electrode. The utility of the rGO/ZrHCF modified electrode was evaluated by determination of nitrite in real samples such as well water and tap water. Continuous addition method was used with three parallel experiments and the results are summarized in (Table.
1). The recovery of sodium nitrite was in the range of 97.73-102.8% with satisfied result and hence the proposed sensor can be suggested for the determination of sodium nitrite in real samples.
