# Highly Sensitive Non-Enzymatic Detection of Glucose at MWCNT-CuBTC Composite Electrode
## 3 Results
### Anperometry Measurements  
Taking into account the usefulness of the amperometry technique for practical electrodetection applications, chronoamperometry (CA) was performed for glucose detection, based on the existing, well-established essential point of reference provided by the voltammograms. The amperometric response of the MWCNT-CuBTC composite electrode, obtained for the successive and continuous addition of 1 mM of glucose in a stirring 0.1 M NaOH solution under the conditions of batch system analysis (BSA) at an applied potential of +0.6 V versus the SCE, is shown in Figure 6. The current response of the glucose oxidation increased linearly within a concentration range from 1 mM to 8 mM (inset of Figure 6). This technique allowed us to reach electroanalytical parameters lower than those achieved using the explored CV studies (see Table 2) because of the electrode fouling effect.  
Figure 5: Differential pulse voltammetry (DPV) recordings at the MWCNT-CuBTC composite electrode in 0.1 M of NaOH supporting electrolyte (curve 1) and in the presence of various glucose concentrations from 1 mM to 6 mM (curves 2–7) under the following operating conditions: MA of 0.002 V and SP of 0.01 V. The inset shows the calibration plots of the current, recorded at +0.27 V/SCE versus the glucose concentration.  
In order to avoid electrode fouling and to enhance the electroanalytical parameters for amperometric detection of the glucose, the multiple pulse amperometry (MPA) technique was applied as a variant of chronoamperometry. The MPA technique combined the anodic detection process with anodic cleaning and cathodic reactivation through alternating the pulsing potential at fixed time ranges. By this technique, in situ cleaning and reactivation of the electrode surface was assured, allowing enhancement of the electroanalytical parameters of the amperometric detection technique. Using CV as reference, MPA was applied under the following conditions:  
* +1.25 V/SCE for a duration of 100 ms, where the copper oxide was formed under the O\({}_{2}\) evolution range;
* +0.6 V/SCE for a duration of 50 ms, where glucose was oxidized;
* -0.5 V/SCE for a duration of 100 ms for copper reduction assurance.  
The results are presented in Figure 7, and the linear dependence between the current and the glucose concentration was reached only at the potential value of +0.6 V/SCE (detection potential), while for other potential levels, no linear dependence was reached due to the specific processes occurring that allowed in situ electrode surface renewing.  
The electroanalytical parameters for the non-enzymatic direct detection of glucose at the MWCNT-CuBTC composite electrode in 0.1 M of an NaOH supporting electrolyte are gathered in Table 2.  
The limit of detection (LOD) was calculated as three times the standard deviations of the intercept (S\({}_{\text{a}}\)) divided by the slope of the regression line (b), while the limit of quantification (LQ) value was estimated as ten times the standard deviations of the intercept (S\({}_{\text{a}}\)) divided by the slope of the regression line (b) [33; 34].  
Figure 6: Chronoamperometry (CA) recordings at the MWCNT-CuBTC composite electrode in 0.1 M of NaOH supporting electrolyte and in the presence of various glucose concentrations from 1 mM to 6 mM under stirring conditions. The inset shows the calibration plots of the current recorded at +0.6 V/SCE versus the glucose concentration.  
When compared with other copper-based electrodes, the MWCNT-CuBTC composite electrode showed superiority in terms of its high sensitivity for glucose detection, as listed in Table 3.