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A carbon paste electrode modified with a cobalt(II) coordination polymer for the direct voltammetric determination of tryptophan |
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| Authors: | Wei Li Changhong Li Yunfei Kuang Peihong Deng Shaohua Zhang Jinsheng Xu |
| Affiliation: | 1. Department of Chemistry and Material Science, Hengyang Normal University, Hengyang, 421008, China 2. Department of Material and Chemical Engineering, Hunan Institute of Technology, Hengyang, 421002, China |
| Abstract: | We have synthesized a cobalt(II) coordination polymer and have characterized it by various methods including X-ray single crystal structural analysis. The polymer was used as modifier to fabricate a carbon paste electrode that displays electrochemical activity towards tryptophan (Trp). Trp is oxidized at the surface of the electrode in buffer solution of pH 4.2, yielding a single peak at 814 mV. The experimental conditions such as the concentration, the composition and the pH values of the supporting electrolyte, accumulation time, and the scan rate were optimized. Under the optimized conditions, the current of peak is linearly related to the concentration of Trp in the range from 0.2 to 8.0 μM, and from 8.0 to 80.0 μM. The detection limit (at S/N?=?3) is 0.1 μM at an accumulation time of 60 s. The determination of Trp in amino acid injection solutions was evaluated and the results were satisfactory. The recoveries were in the range of 97.5% to 103.0%. As shown in Fig. 1, a well-defined and very sharp oxidation peak at 814 mV was obtained in the curve the curve b. Whereas, a relatively weak anodic peak at 835 mV can be observed under the same conditions with an bare electrode. By comparing curve b and c, it can be seen that, the peak current was about 0.720 μA with the bare CPE. However, the peak current was increased to 10.39 μA with the modified CPE. This significant improvement of peak current may be related to the effective catalytic fashion of the cobalt (II) coordination polymer film modified on the surface of the CPE in the electrochemical oxidation of Trp. |
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