| Synthetic colorants are kinds of food additives, widely applied to change or added food colour or lustre because of their stable nature, strong tinting, low costing, easying toning and so on, compared with natural colorants. But synthetic colorants mainly come from coal chemical industry or its byproducts, they have potential toxicity and pathogenicity, so the monitoring of synthetic colorants in foods is very important. Herein, an electrochemical sensor for rapid and simple detection of synthetic colorants was constructed using multi-wall carbon nanotube (MWNT) sensing film. Major work is as follows:1. A muti-walled carbon nanotube composite film modified electrode (MWNT/DHP/GCE) was achieved for simultaneous enhanced the oxidition peaks of Poncau 4R and Allura Red, then the electrochemical behaviors of Poncau 4R and Allura Red have been studied carefully. However, two independent oxidation peaks were observed at 0.56 V and 0.68 V at the MWNT modified GCE. Further studies show that their oxidation have been significantly increased. As a result, a sensitive, rapid and convenient electrochemical method was developed for the determination of Poncau 4R and Allura Red. The limits of detections are 15μg L-1 (2.48×10-8 mol L-1) and 25μg L-1(5.04×10-8 mol L-1), respectively, and the linear ranges of the two synthetic colorants are over the range from 25μg L-1(4.14×10-8 mol L-1) to 1.5 mg L-1(2.48×10-6 mol L-1), 50μg L-1(1.01×10-7 mol L-1) to 2.5 mg L-1(5.04×10-6 mol L-1) respectively. The new method was used to determine the content of Poncau 4R and Allura Red in soft drinking samples, and satisfactory average recoverys were 95.2% to 101.7% and 97.9% to 100.6%.2. The electrochemical behavior of Quinoline yellow has been examined. Compared with the unmodified eletrodes, the MWNT film modified eletrodes significantly increases the oxidation signals of Quinoline Yellow, showing remarkably surface enhancement effects and strong adsorption ability. The effects of pH value, amount of MWNT, accumulation potential and time on the oxidation signals of Quinoline Yellow were studied. Thus, a novel electrochemical method was proposed for the determination of Quinoline Yellow. The linear range of the colorant is from 1 mg L-1(2.09×10-6 mol L-1) to 20 mg L-1(4.19×10-5 mol L-1), and the limit of detection is as low as 0.2 mg L-1(4.19×10-7 mol L-1). Finally, the proposed method was employed to determine Quinoline Yellow in drinks and wine, there is a good consistency compare with high performance liquid chromatography. |
