Reduced-graphene And Bismuth Film Modified Electrodes In The Application Of Detection Of Heavy Metals In Food

With rapid development of world industrialization, heavy metals issues became the most frustrating consequence of industrial development. From cadmium pollution of Longjiang,ocurred in Guangxi Province, the incident of children blood lead exceeding in Hunan, to the Minamata disease caused by mercury pollution and the itai-itai disease caused by cadmium pollution happened regionally in the last century Japan. Heavy metal pollution has become an international problem to which need everyone to pay attention.And food is one of main approaches that heavy metals enter into human bodies, so cultivating and perfecting the detection methods for heavy metals is the primary assurance to control possible damages and protect people from further hazards. The regular and trustworthy detection methods for heavy metals are atomic absorption method, mass spectrum method, and fluorescent spectrum method, etc. These methods were recognized of high sensitivity and good accuracy. However, these detection methods still exist some obvious shortcomings: Large and expensive equipments which need sophisticated operators and daily costly maintenance are the most common disadvantage of these regular methods; meanwhile, simultaneous determination of variety heavy metal elements in food samples cannot achieved by some of these demanding methods because they can only determine a single element once. Therefore, this paper established two rapid methods for simultaneous determination of several heavy metals with highly sensitive electrochemical sensors.(1) Building a differential pulse stripping voltammetry with bismuth film modified electrode for lead and cadmium detection simultaneously in food: At first, prepare a bismuth film modified electrode in situ plating. Then the electrochemical behaviors of lead and cadmium on this electrode were investigated. And the test conditions were already optimized during experiments. Lead’s linear domain ranges from 1.0×10-5 g/L to 5×10-4 g/L and detection limit is 4.6×10-6 g/L; cadmium’s linear domain ranges from1.0×10-5 g/L to 2×10-4 g/L and detection limit is 1.0×10-5 g/L. There is no significant differences between the results of differential pulse stripping voltammetry with bismuth film modified electrode and GFAAS. The studied method has been applied to the detection of lead and cadmium in rice samples with a satisfied result with average recoveries are 95.5%~104.0%(lead) and 96.2%~103.1%(cadmium).(2) Building a differential pulse stripping voltammetry with reduced graphene modified electrode for lead, cadmium and copper detection simultaneously in food: Reduced graphene was applied to modification of glassy carbon electrode as a new nano material. Firstly, the electrochemical characteristics of reduced graphene were studied to ensure graphene the right material for differential pulse stripping voltammetry. After that, graphene nanosheets were directly deposited onto a glassy carbon electrode through potential-time reduction of 1.0mg/m L graphene oxide colloidal solution. Then test conditions were already optimized during experiments. Lead’s linear domain ranges from 1.0×10-8 g/L to 7×10-4 g/L and detection limit is 1.4×10-9 g/L; cadmium’s linear domain ranges from 1×10-8 g/L to 2×10-4 g/L and detection limit is 3.0×10-9 g/L; copper’s linear domain ranges from 1.0×10-7 g/L to 3×10-3 g/L and detection limit is 1.6×10-8 g/L.(3) According to buying habit of local people’s, we selected 40 kinds of food from three Wuxi markets. And simultaneously detection of lead, and cadmium, and copper in 40 food samples was completed by stripping voltammetry with a reduced graphene modified electrode. The studied method has been applied to the detection of lead, cadmium, copper in samples with a satisfied result with average recoveries are 90.1%~115.1%(lead) and 87.7%~114.2%(cadmium), 90.2%~110.6%(copper). There is no significant difference between the results of differential pulse stripping voltammetry with a reduced graphene modified electrode and GFAAS was found. It turned out stripping voltammetry with a reduced graphene modified electrode is not only convenient and economic, but also highly sensitive and easy-to-use.For simultaneous detection of three kinds of heavy metals, reduced graphene modified electrode is more superior to GFAAS relatively and a technical support for control of various heavy metals in food, and can play a significant role in food safety.