Risperidone Case Study

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3. Results and discussion 3.1. Influence of pH The electrochemical behavior of risperidone is be influenced by the pH value of the aqueous solution, since the electrochemical characteristics of poly(MImEO8BS)-Ni nanocomposites are independent of pH. Accordingly, pH optimization of the solution seems to be important in order to receive the voltammetric oxidation of risperidone. Consequently, the electrochemical behavior of risperidone was studied in 0.1 M PBS with variant pH values (2.0<11.0) at the surface of NCPMNINGCE by voltammetry. It was found that the voltammetric oxidation of risperidone at the surface of NCPMNINGCE was more favorite under neutral conditions than in acidic or basic medium. Thus, the pH 7.0 was selected as the optimal…show more content…
3 describe the electrochemical oxidation of 300.0 µM risperidone at unmodified GCE (curve b), NINCPE (curve c), PMNGCE (curve d), and NCPMNINGCE (curve e). Also, curve a shows unmodified GCE in 0.1 M PBS (pH 7.0). As it is seen, while the anodic peak potential for risperidone oxidation at the NINCPE and unmodified GCE are 950 and 930 mV, respectively, the corresponding potential at PMNGCE and NCPMNINGCE is ~ 870 and 820 mV. These results indicate that poly(MImEO8BS)-Ni nanocomposite can act as a good modifier and peak potential for risperidone oxidation at the NCPMNINGCE, PMNGCE and NINCPE shift by ~130, 110, and 50 mV toward negative values compared to unmodified GCE, respectively. However, NCPMNINGCE shows much higher anodic peak current for the oxidation of risperidone compared to PMNGCE, indicating that the poly(MImEO8BS)-Ni nanocomposite has significantly improved the performance of the electrode toward risperidone oxidation. Also, under experimental condition unmodified GCE in 0.1 M PBS (pH 7.0) showed no peak (Fig. 3 curve a). The efficacy of potential scan rate on the voltammetric oxidation of risperidone at the NCPMNINGCE was studied by LSV (Fig. 4). As can be observed in Fig. 4, the oxidation peak potential Focused on more positive potentials with growing of scan rate, confirming the kinetic limitation in the electrochemical reaction. Also, a plot of peak height (Ip) vs. the square root of scan rate (ν1/2) was investigated to be linear in the…show more content…
Ag/AgCl/KCl (3.0 M) for the various concentrations of risperidone in PBS (pH 7.0) (Fig. 6). ). For an electroactive material (risperidone in this case) with a diffusion coefficient of D, the current detected by the electrochemical reaction at the mass transport limited condition is defined by the Cottrell equation [63]. Experimental plots of I vs. t−1/2 were employed with the best fits for different concentrations of risperidone (Fig. 6A). The slopes of the resulting straight lines were then plotted vs. risperidone concentration (Fig. 6B). From the resulting slope and Cottrell equation the mean value of D was determined to be 5.06 × 10−6

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