The Research Of Heavy Metal' Detection And Pre-treatment Methods In Cereals

Grain quality and safety is closely related to country's security and people's everyday life. Recently with the rich grain harvest, development of standard of living, further cognition to the noxious and side effect of the chemicals, Chinese are so seriously demanding for more healther food that grain quality and safety are payed much more attention than before. Employees in the grain department now are transfering their time and enegy to insure foodstuff quality and safety from emphases weight number while ignoring the quality in the past. The main task and mission which modern grain inspection are facing now is how to quickly test the sanitation target of original grain. Using rice as test object through a modern and new technique to pretreat the object, the conditions which effect the testing of heavy metal ion in rice has been researched in this paper. The results are as followed:1. The inspecting methods of Pb and CdThe best and time-shorten inspecting method has been determined by comparing to differences between single and several heavy metal ion's testing results basing on the different digesting process , reagents, conditions. The results showed us: microwave digesting can greatly decrease the time of digesting, boost the efficiency, lessen the environment contaminated and good for people's health. the conditions of microwave digesting has been optimized using orthogonal design, the results was: three step digesting was better. first step: microwave 04%,pressure 5 atm, time 2 min, temperature 130℃. second step: microwave 05%,pressure 10 atm, time 2 min, temperature 170℃. third step: microwave 07%,pressure 8 atm, time 4 min, temperature 200℃.2.The inspecting method of HgHg was determined by high pressure digesting-atom fluorescence spectrum, and negative high voltage, electric current of the lamp, carry gas, shield gas, reagents of digesting and its dosage, concentration of KBH₄ have been considered. the optimum condition and the method of pretreatment have been determined. The regression equation is:IF=1055.323×C+0.355,r=0.999, detection limit: 0.415μg/kg, linear range:0-2.0ng/mL; average recovery rate of the method: 95.0%-102.0%;RSD:1.0%-6.5%.The results were satisfied. 3. The inspecting method of inorganic arsenicThe concentration of KBH₄ and loading flow, vibrating, the placed time after constant volume and etc have been researched and the optimum method of determining inorganic arsenic have been decided: KBH₄: 15.0g/L,loading flow:4.0% HCL, the placed time after constant volume:30 min, linear range:0-200ng/mL;r=1.000;detection limit: 0.038μg/L, average recovery rate of the method: 95.5%-101.9%; RSD:1.4%-2.4%.The method can be using to determined the content of inorganic arsenic in the rice which is accurate, rapid and sensitive.