# Highly Sensitive Non-Enzymatic Detection of Glucose at MWCNT-CuBTC Composite Electrode
## 3 Results
### Differential Pulse Voltammetry (DPV) Measurements  
Differential pulse voltammetry (DPV) was employed as a technique for the evaluation of the performance of the MWCNT-CuBTC composite electrode for glucose determination. Various operating conditions in relation to the modulation amplitudes (MAs) and the step potentials (SPs) were tested, and the best results were gathered for an MA of 0.002 V and an SP of 0.01 V. Figure 5 shows the DPV recordings for the glucose concentration ranging between 1 and 6 mM and in the potential range of +0.1 V to +0.6 V versus the SCE. The shape of the differential pulse voltammogram was very different in comparison with the CV and LSV results at the potential values of +0.27 V/SCE and +0.44 V/SCE. Two very clear oxidation peaks appeared, with their heights increasing progressively with the glucose concentration. Since the lowest potential in the electroanalysis was desired for analyte detection, the potential value of +0.27 V/SCE was selected for the calibration. Additionally, this peak height was higher in comparison with the second one recorded at +0.44 V/SCE. The useful net current signals  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Peak Potential** & **Technique** & **Concentration** & **Sensitivity** & **Correlation** & **LOD** & **LQ** & **RSD [**\({}^{**}\)**]** \\
**(V/SCE)** & **Used** & **Range (mM)** & **(mAmM\({}^{-1}\))** & **Coefficient (R\({}^{2}\))** & **(mM)** & **(mM)** & **(\%)** \\ \hline +0.60 & CV & 0.1–1 & 2.290 & 0.950 & 0.010 & 0.003 & 0.683 \\ +0.60 & CV & 1–10 & 0.620 & 0.983 & 0.020 & 0.066 & 0.683 \\ +0.60 & LSV & 1–10 & 0.119 & 0.992 & 0.065 & 0.218 & 4.031 \\ +0.60 & Prec./LSV & 0.2–1 & 0.587 & 0.996 & 0.010 & 0.035 & 2.450 \\ +0.27 & DPV & 1–6 & 0.001 & 0.997 & 0.030 & 0.100 & 4.000 \\ +0.60 & CA & 1–8 & 0.064 & 0.990 & 0.025 & 0.100 & 3.140 \\ +0.60 & MPA & 0.2–1 & 2.926 & 0.967 & 0.005 & 0.015 & 3.500 \\ \hline \end{tabular}
\end{table}
Table 2: The electroanalytical parameters for glucose direct detection at the MWCNT-CuBTC composite electrode in 0.1 M of NaOH supporting electrolyte.  
Figure 4: LSV recordings at the MWCNT-CuBTC composite electrode in 0.1 M of NaOH supporting electrolyte (curve 1) and in the presence of 1 mM of glucose at various accumulation times from 0 to 50 min (curves 2–11). The inset shows the evolution of the anodic peak current and the enhancement factor versus the accumulation time.  
corresponding to the oxidation peak recorded at +0.27 V/SCE were linearly dependent on the glucose concentration (inset of Figure 5).  
The potential usefulness of the DPV method for the determination of glucose content in real sample solutions was verified using aqueous solutions from a physiological serum of glucose containing 25 g glucose/500 mL serum and 5 mg glucose/100 mL serum, respectively (Hemofarm, Romania). The values of 24.5 g glucose/500 mL serum and 5.05 mg/100 mL serum represented the average content, determined using the anodic DPV technique at the MWCNT-CuBTC composite electrode associated with the standard addition method, which indicates a recovery degree of 98% and 101% respectively, indicating good recovery and reproducibility of the detection results of the glucose.