Detection Of Heavy Metal Based On Enzyme Inhibition Method With Micro-calorimetry

The food safe problem has become a key issue around the world. With the development of industrial and agricultural manufacture, food contamination is becoming more serious, especially for heavy metals contamination. The residual time of most heavy metals in soils and plants is very long. Once taken through plants, heavy metals can enter the food chains. Hence, people could be at risk of healthy problems due to consuming food grown in soils which contains heavy metal. Much more studies have been conducted for the determination of heavy metals in food over the world. Therefore, it is practically important for the detection of toxic heavy metals in different kinds of food and water to evaluate food quality, protect human health and promote sustainable development of economy and society.The paper focuses on the impact of heavy metal ions on urease-catalyzed reaction with micro-calorimetry under different conditions. Furthermore, some basic thermal parameters of calorimetric biosensor are also considered here. The main contents are as the following.(1) Inhibiting effects of heavy metal ions on urease-catalyzed reaction are investigated with micro-calorimetry. Further, the joint inhibition effects of two heavy metal ions on urease-catalyzed reaction are also conducted. The results indicate that, with a wide range of concentration (0.1,1,10,100and103mg/L), heavy metal ions on urease hydrolysis reaction was not only have the effect of inhibition, but also can promote this reaction in some concentration range. The correlations between urease inhibition rate and concentration of heavy metal ion are very significant, and the inhibition effects are:As3+> Pb2+> Cd2+> Cu2+. The joint inhibition is close to that with higher inhibition when two heavy metal ions were used together.(2) The flow cell of Micro DSC III is used for the enrichment and detection of heavy metal ions. Based on the flow injection analysis, the enrichment heat releasing of heavy metal ion, and the impact of the enrichment on immobilized enzyme catalysis are concerned about, and can lead to better detection results in some condition, for example, when using low flow rates (O.lml/min), the carrier resin particle size of0.5-0.6mm, urease injection concentration of3ml, heavy metal ions volume of5ml. (3) According to the characteristics of the reactor biological sensors, the heat transfer experiment system of miniature fixed bed is also built for studying transient and steady temperature distribution when low flow distilled water flows through longitudinal and radial of miniature fixed bed under the constant wall temperature. The results show that even if in very low flow, there is still apparent entrance effect in miniature fixed-bed, that is, temperature distribution is uneven around the fluid entrance area. However, along with the higher of the fixed-bed, this effect will decrease rapidly. Thermal conductivity of resin used in the experiments is very low, resulting in the effective heat transfer parameters is relatively small, therefore, it is necessary to select miniature particle with good thermal conductivity as a biological carrier, which is beneficial to signal detection of the heat transfer and provide the basic parameter for developing micro-biosensors.