# Development of Heavy Metal Potentiostat for
## 3 Results and Discussion
### Heavy Metal Detection Test  
Figure 6a shows the stripping peak of 10 ppm Cd\({}^{2+}\) and 10 ppm Pb\({}^{2+}\). Based on the figure, the Cd\({}^{2+}\) and Pb\({}^{2+}\) stripping peaks were observed at \(-\)0.30 and \(-\)0.25 V, respectively, and the peaks were located quite close to each other. This was due to the fact that detection was done using a gold-based electrode. With regard to this, there were several studies which reported that closer stripping peaks were observed for Cd\({}^{2+}\) and Pb\({}^{2+}\) under gold-based electrodes and the presence of both metals in the solution caused overlapping of the stripping peaks [33; 34; 35]. Moreover, the presence of Cd\({}^{2+}\) in Pb\({}^{2+}\) measurements will affect the stripping intensity of Pb\({}^{2+}\) and vice versa [33]. Figure 6b shows the stripping peaks of Cd\({}^{2+}\) and Pb\({}^{2+}\) extracted from [34] were close to each other and simultaneous detection of Pb\({}^{2+}\) and Cd\({}^{2+}\) will cause overlapping of the stripping peaks.  
Figure 6a also shows that the current intensity of the Cd\({}^{2+}\) stripping peak versus Pb\({}^{2+}\) was significantly smaller, in which the peak current of Cd\({}^{2+}\) was 74 \(\mu\)A and the peak current of Pb\({}^{2+}\) was 148 \(\mu\)A. This indicated that the HMstat has higher sensitivity to detect Pb\({}^{2+}\) compared to Cd\({}^{2+}\). Similar results were also observed in [35] and as shown in Figure 6b [34], where the peak current of Pb\({}^{2+}\) obtained was more elevated than Cd\({}^{2+}\).  
The same experimental procedures were repeated using Rstat. The detection results of HMstat were compared with Rstat. Referring to Figure 7, using Rstat, the stripping peak of Cd\({}^{2+}\) and Pb\({}^{2+}\) were located at \(-\)0.25 and \(-\)0.3 V, respectively. These results were the same when compared to HMstat. As expected, the peak current of the Pb\({}^{2+}\) using Rstat and HMstat was quite similar (136 and 148 \(\mu\)A for Rstat and HMstat, respectively). However, the peak current of Cd\({}^{2+}\) (297 \(\mu\)A) using Rstat showed significantly higher value when compared to the result obtained by the HMstat. It was also observed that using Rstat, the peak current of Cd\({}^{2+}\) was higher when compared to the Pb peak, which indicated that Rstat has a higher sensitivity to detect Cd\({}^{2+}\) when compared to Pb\({}^{2+}\). This result is in contradiction with the result obtained in [35] and in Figure 6b [34].  
Based on the above results, the stripping peak of simultaneous detection of Cd\({}^{2+}\) and Pb\({}^{2+}\) under gold-based electrode using both HMstat and Rstat interfered with each other's peaks. This can be overcome by electrode modification to improve anti-interference of the electrode by diminishing either one stripping peak [36], or by implementing a chemometrics method such as back-propagation artificial neural network (BP-ANN) using the formation of a prediction model for detection Cd\({}^{2+}\) and Pb\({}^{2+}\)[37].  
Figure 6: (**a**) Stripping peak of Cd\({}^{2+}\) and Pb\({}^{2+}\) using HMstat incorporated with a screen-printed gold electrode (SPGE). Experimental condition: deposition potential \(-\)0.6 V; deposition time 120 s; modulation and step amplitude 50 mV and frequency 10 Hz. In 0.1 M acetate buffer. (**b**) Stripping peak of Cd\({}^{2+}\) (at \(-\)0.195 V) and Pb\({}^{2+}\) (at \(-\)0.18 V) under gold-based electrode, extracted from previous research [34].