# Induced Effect of Gold Nanoparticles (AuNPs) and Halide Ions on Pyridoxine Molecule Stability
## 3 Results and Discussion
### The Influence of Chloride Ions on Electrochemical Behavior of Pyridoxine  
Chloride ions are part of the active electrolytes, so they participate in the electrode processes [38,39]. Under these conditions, the processes are different from the case of fluoride ions, ions that are electrochemically inactive. Cyclic voltammetry responses of gold electrode in binary electrolyte solutions, NaCl_B6, NaCl_AuNPs and ternary NaCl_B6_AuNPs are shown in comparison to those of the individual support electrolyte (NaCl) in Figure 5. \begin{table}
\begin{tabular}{c c c} \hline
**Experimental Conditions** & **Kinetic Model** & **k** \\ \hline B6 individual & zero-order reactions & 0.0006 u.Abs. \(\times\) min\({}^{-1}\) \\ B6 in the presence of AuNPs & first-order reactions & 0.005 min\({}^{-1}\) \\ AuNPs individual & zero-order reactions & 0.0048 u.Abs. \(\times\) min\({}^{-1}\) \\ AuNPs in the presence of B6 & first-order reactions & 0.004 min\({}^{-1}\) \\ \hline \end{tabular}
\end{table} 
Table 1: Kinetic parameters for B6 and AuNP electrochemical degradation, individual and mixed. Figure 4: The kinetic models of the zero- and first-order reactions applied for B6 (**a**) and gold nanoparticles (**b**) electrochemical degradations. The cyclic voltammograms in Figure 5 show an intensification of the electrode processes in the field of high anodic overvoltage. At a working electrode potential greater than 0.8 V, the current densities increase significantly. The cyclic voltammogram indicates a wide, clearly contoured peak of the anodic current density, between 0.8 and 1.7 V, specific to the oxidation of the gold electrode surface. This anodic peak retains its shape in the absence and presence of pyridoxine molecules but shows small changes in its characteristics. This anodic oxidation peak, although very wide, includes both the processes of the metal surface and the processes of organic molecules, clearly highlighted by the spectrophotometric analysis associated with cyclic voltammetry. The very high hysteresis of the cyclic voltammogram, recorded in the presence of chloride ions, indicates a very high susceptibility to oxidation and is due to the much higher aggressiveness of these ions. In this potential field, the oxidation of chloride ions also takes place, with the electrochemical generation of active chloride species, for example hypochlorite, chlorite, chlorate and perchlorate anions [50,51,55]. Anodic current densities increase 10 times more than in the case of fluoride ions, but in both cases, the current densities are reduced by the addition of gold nanoparticles. The presence of AuNPs in the electrolyte solution leads to a decrease in both anodic and cathodic current densities. The presence of pyridoxine molecules in the electrolyte solution results in increased anodic current densities, associated with the electrooxidation of organic molecules on the surface of the gold electrode. The cathodic peak recorded at the potential of 0.0 V is observed only in the absence of gold nanoparticles. This peak is of the irreversible type and, consequently, depends on the nature and composition of the electrolyte solution. Under these conditions, the structure and composition of the layer formed on the surface of the gold electrode may be different. The results of the spectrophotometric analysis of the electrolyte solutions, before--b and after--a, the recording of cyclic voltammograms are represented in Figure 6.  
Figure 5: Cyclic voltammetry responses of gold electrode in 0.1 mol \(\times\) L\({}^{-1}\) NaCl support electrolyte in the absence and in the presence of 75 mg \(\times\) L\({}^{-1}\) gold nanoparticles (AuNPs) and 2.9 \(\times\) 10\({}^{-4}\) mol \(\times\) L\({}^{-1}\) pyridoxine (vitamin B\({}_{6}\)). The UV-Vis spectrum of the support electrolyte solution, 0.1 mol \(\times\) L\({}^{-1}\) NaCl, shows an increase in absorbance at wavelengths less than 270 nm due to the presence of oxygen-genated chlorine compounds.