CVs in 0.1 M KCl solution with and without CA at bare GCE and CuGeO3 nanowire modified GCE are measured in the potential ranging from −1.0 to +1.0 V (Fig. 2). The potential scan rate is 50 mVs−1. No CV peaks are observed from the CV curves at the nanowire modified GCE in 0.1 M KCl solution without CA. Therefore, no electrochemical activity is shown at the CuGeO3 nanowire modified GCE in 0.1 M KCl solution without CA. It is very interesting that two pairs of CV peaks are observed from the electrochemical CV curve in 0.1 M KCl solution with 2 mM CA. Two semi-irreversible electrochemical CV peaks are observed. The anodic CV peaks (cvp1, cvp2) are located at 0.21 V and 0.01 V, respectively. And two cathodic CV peaks (cvp1′, cvp2′) are located at 0.02 V and −0.52 V, respectively. These CV peaks can only be shown from KCl solution with CA at the CuGeO3 nanowire modified GCE. Therefore, it is believed that the electrochemical CV peaks originate from the CA. CuGeO3 nanowires have an essential role for the formation of the electrochemical CV peaks. Two pairs of CV peaks are similar to those at the CuGeO3 nanowire modified GCE in KCl solution with 2 mM tartaric acid and cysteine, respectively [13,15]. However, the potentials of the CV peaks are different. Two anodic CV peaks (cvp1, cvp2), located at 0.26 V and −0.04 V, and two cathodic peaks (cvp1′, cvp2′), located at −0.15 V and −0.35 V, were obtained at the CuGeO3 nanowire modified GCE for the analysis of cysteine, respectively . Two anodic CV peaks (cvp1, cvp2) were located at 0.18 V and 0.02 V from the CV curve of 2 mM tartaric acid. Two cathodic peaks (cvp1′, cvp2′) were located at 0.05 V and −0.33 V, respectively . Thus, the CA and cysteine can be distinguished via the potentials of the CV peaks by CV method. The results show that CuGeO3 nanowires have different electrochemical activity in KCl solution with CA. In order to demonstrate whether the anodic and cathodic CV peaks are semireversible electrochemical reaction process, the experiments with initial potential scan direction and different reversal potential were conducted. The potentials and intensities of the electrochemical CV peaks maintain very similar when changing the initial potential scan direction and reversing the potential scan at different positive potential. Therefore, the cvp1 and cvp2 are considered to be caused from the potential of cvp1′ and cvp2′, respectively.