The Development Of Electrochemistry Sensor Methods For Fast Detection Of Lead, Cadmium, Copper In Food

Heavy metal contamination in food is becoming more and more serious and threatening food safety and human health. The contamination is mainly caused by natural geographical factors, pollution from environment, food processing and transportation. The effective detection methods for heavy metals in foods are the key points for ensuring food safety. Routine methods for the detection of heavy metals mainly include atomic absorption spectrometry, ICP-AES, spectrophotometry, which usually have high sensitivity and accuracy, but these methods require professional large scale instrument, complex and time-consuming operation as well. Furthermore, they can hardly meet the requirements of quick and on-site detection for large amounts of samples. In this study, two types of sensor methods were established for the detection of Lead, Cadmium and Copper in food samples and the effects of the methods were evaluated. The investigating process of the sensors and the detecting results were summarized as follows:1. Development of amperometric sensor based on Nafion-MWCNT modified electrode. The electrochemical behaviors of lead, cadmium and copper on the modified glassy carbon electrode (GCE) were investigated and the sensor signals were recorded using stripping voltammetry. The conditions and performance of the sensor was optimized. The results showed that the response of the amperometric sensor to the concentration of lead and cadmium displayed a linear correlation over a range from 0.01 mg/L to 1 mg/L with a detection limit of 2μg/L. The average recovery was 95.8% and 95.0%, respectively and the detection time was about 5 minutes.The accuracy rate was 95%, 100% and 100%, respectively. The response of copper displayed a linear correlation over a range from 0.01 mg/L to 1 mg/L with a detection limit of 2μg/L. The average recovery was 96.4% and the detection time was about 4 minutes. Using disposable screen-printed electrodes not only can achieve the same effects with a satisfactory reproducibility and stability as glassy carbon electrode, but also is quicker and easier to operate.2. Development of amperometric sensor based on bismuth film modified electrode. Bismuth modified GCE was made by coating bismuth nitrate on the glassy carbon electrode based on polymerization. The electrochemical behaviors of lead and cadmium on the modified GCE by bismuth were investigated and the sensor signals were recorded using stripping voltammetry. The conditions and performance of the sensor was optimized. The results showed that the response of the amperometric sensor to the concentration of lead displayed a linear correlation over a range from 0.001 mg/L to 1 mg/L with a detection limit of 0.2μg/L. The average recovery was 94.8% and the detection time was about 6 minutes. The response of cadmium displayed a linear correlation over a range from 0.1 mg/L to 1.2 mg/L with a detection limit of 50μg/L. The average recovery was 97.3% and the detection time was about 6 minutes. The accuracy rate was 100% and 100%, respectively.In summary, the electrochemical sensor methods based on the electrode modified with Nafion-MWCNT and bismuth film for detecting the above 3 heavy metals in food are quick , simple and sensitive, able to meet the requirements of detection for large amount of food samples on-sites after a further optimization, and can play an important role in ensuring food safety.