Development Of Photoeletriacal Sensor For Detecting Chormium (Ⅵ), Cadmium, Copper, Mercuryin Food

Heavy metal pollution in food caused by environmental pollution,food processing and transportation is serious now and damage human health. So,effective detection technologies for heavy metals are urgent and necessary to ensure food safety.The main traditional detecting methods for heavy metals include atomic absorption, spectrophotometry and plasma mass spectrometry and other methods,which have the strengths with low detection limit,high sensitivity, but these methods require difficult operation,complex sample pretreatment,long testing time, large-scale instrument, and can't realize online sample testing.Due to the number of food samples is so large, developing a rapid, effective and accurate testing technology for heavy metals is urgent and important. In this study, the photoelectrical biosensing methods were established for detecting Chromium,Cadmium, Copper, Mercury in food samples and the evaluation of the analytic performance was also conducted. The specific research process and the results are as follows:1. Development of photoelectrical sensor for detecting Chromium (VI) in food. Based on the special color reaction between diphenylcartazide and chromium, diphenylcartazide was used as chromogenic agent and immobilized on a self-made test strip.After the test strip was inserted into photoelectrical sensor, samples were added to the reaction area of the strip.Then the light reflection was recorded as the sensor singal. A standard calibration curve was established between the light reflection and the chromium concentration in standard solution. The results showed that this sensor could detect chromium with the concentration over the range from 0.1 mg/L to 30 mg/L with the detectable limit of 0.05 mg/L, the operating time was within 5 min,the recovery rate and accurate rate were 93% and 94%, respectively.2. Development of photoelectrical sensor method for determination of cadmium in food. A test strip for the detection of cadmium were made and fabricated by immobilizing 1-(4-nitrophenyl) -3- (3-methyl-pyridyl) triazene, a chromogenic agent specificically for cadmium. The test strip was inserted into a photoelectrical sensor, the light reflection was recorded as the sensor singal. A standard calibration curve was established between the light reflection and the cadmium concentration in standard solution. The results showed that this sensor could detect cadmium with the concentration over the range from 1 mg/L to 70 mg/L with the detectable limit of 0.5 mg/L, the operating time was within 5 min, and the recovery rate and accurate rate were 87% and 94%, respectively.3 Development of photoelectrical sensor for determination of copper in food by chemical color reaction. A test strip for the detection of copper were designed and fabricated based on the mechanisms of color reaction between the special chromogenic agent,1-Pyrrolidinecarbodithioic acid and copper in samples.The light reflection recorded by the photoelectrical sensor. A standard calibration curve was established between the light reflection and the copper levels in standard solution. The results showed that this sensor could detect copper with the concentration over the range from 1 mg/L to 100 mg/L with the detectable limit of 0.1 mg/L, the operating time was within 5 min, and the recovery rate and accurate rate were 99.6% and 98%, respectively.4 Development of photoelectrical sensor for determination of copper by Enzyme inhibition reaction in food. Based on the mechanism that copper can decrease the levels of bule substrate produced by the reaction of the Glucose oxidase-horseradish peroxidase-glucose (Glu)-o-tolidine (OT) coupling reaction system due to copper inhibites the activities of glucose oxidase, a self-made test strip was fabricated by immobilizing glucose and o-tolidine. The test strip was inserted into the photoelectrical sensor, the light reflection was recorded as the sensor singal. A standard calibration curve was established between the light reflection and the copper concentration in standard solution, and the method for detecting copper was established.The results showed that this sensor could detect copper with the concentration over the range from lmg/L to 100 mg/L with the detecting limit of 0.1mg/L, the assay time was within 8 min, and the recovery rate and accurate rate were 89% and 88%, respectively.5 Development of photoelectrical sensor for determination of Mercury(Ⅱ) in food. Based on the mechanism that mercury inhibits glucose oxidase and Glucose oxidase-horseradish peroxidase-glucose (Glu)- o-tolidine (OT) coupling reaction system and produces blue substrate, a kind of test strip for detecting trace mercury was developed by immobilizing glucose and o-tolidine. Once the test strip was inserted into a photoelectrical sensor, the light reflection intensity was recorded and shown by the sensor. A standard calibration curve was established between light reflection intensity and mercury levels, which showed a good linear relationship between them when the range of mercury concentration was lmg/L to 10 mg/L. By this sensor method, the detection limit can be achieved 0.02mg/L, and the detection time was within 8 min, and the recovery rate and accurate rate were 91% and 98%, respectively.In conclusion,the methods for detecting the above 4 heavy metals are quick simple and sensentive, and can meet the requirments of detection of them in food. Hopefully, the photoelectric sensor can be used on-site inspection of heavy metals pollution.