| The rare earth elements are lanthanide elements in the periodic table of chemical elements-La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Y and Sc composed of 17 species.Due to its superior geological environment,China has become one of the countries with the richest rare earth resources in the world.As China’s rare earth resources are widely used in industrialproduction,rare earth elements will inevitably enter the food chain and human body through the environment.Rare earth itself has the function of environmental accumulation,selective absorption and enrichment of animal organs,and has potential toxic and side effects on animals and their products.Pork,poultry,shrimp and other meat products may be directly or indirectly contaminated by rare earth elements.How to accurately and reliably detect their rare earth elements residues is of great significance for food safety.In this study,ICP-MS and ICP-OES methods were explored to detect rare earth elements,the sample pretreatment methods and procedures were optimized,the internal standard method and external standard method were compared,and the actual samples were measured.The results are as follows:1.Selection of test and analysis instruments: the test samples were digested by microwave,and Rh and Re were used as internal standard elements ICP-OES and ICP-MS were used for determination.The results showed that the correlation coefficient of ICP-OES curve was greater than 0.9995,the detection limit was between 0.4 μ g / L and 1.2 μ g / L,the relative deviation(RE)was between 2.1% and 17.6%;the correlation coefficient of ICP-MS curve was greater than 0.9998,the relative deviation(RE)was between 0.64% and 10.0%,and the detection limit was between 6ng / L and 63 ng / L.the linearity,sensitivity and accuracy of ICP-MS were better than those of ICP-OES.It is confirmed that ICP-MS has the advantages of higher sensitivity,high accuracy and low detection limit for trace or even ultra trace rare earth elements in meat food,which is more suitable for the analysis of trace or even ultra trace rare earth elements in meat food.2.Microwave digestion reagent dosage,and Parameter Optimization: Weigh 0.5g(accurate to 0.001)of national standard material prawn,pig liver and chicken respectively,and select different amounts of reagent HNO3(3.0,4.0,5.0,6.0,7.0,8.0)m L、H2O2(0.5,1.0,1.5,2.0,2.5,3.0)m L 、The samples were digested with different retention time(5,10,15,20,25,30)min,determined by ICP-MS internal standard method.The optimal amount of microwave digestion solvent is 6.0m L HNO3 + 2.0m L H2O2,and the optimal ho Lding time is 20 min when heating to the optimal digestion temperature(185 ℃).3.Optimization of internal standard elements: the selected standard samples were digested by microwave after optimization,and determined by ICP-MS with RH,re internal standard system and Rh,re,in internal standard system.The results showed that when RH,re and in were used as internal standards,the correlation coefficients of the curves were greater than 0.99990,the detection limit of the method was between 4.7ng/L and 44 ng / L,and the relative deviation(RE)of the measurement results was between 0.64% and 7.6%;when RH,re and in were used as mi×ed internal standards,the corre Lation coefficients of the curves were greater than 0.9998,the relative deviation(RE)was between 1.3% and 9.1%,and the detection limit of the method was between 5.5ng/L and 60ng/L.The internal standard system for matrix correction of interference elements with RH,re and in was determined.4.Selection of ICP-MS internal standard method and external standard method: The sample was digested by microwave,and Rh,re and in were used as internal standard components for matrix correction.The interference elements were determined by ICP-MS internal standard method and external standard method respectively,The results showed that the correlation coefficient r of standard curve of external standard method was greater than 0.9995,and the detection limit was 3.9 Results the relative standard deviation(RSD%)was between 2.8% and9.2%.The correlation coefficients of the standard curve of the internal standard method were greater than 0.99990,the detection limit was between 2.4ng/L and 48 ng / L,and the recovery of the sample was between 90.2% and 103.5%.Results the relative standard deviation(RSD%)was between 0.7% and 4.2%.The internal standard method has higher precision,accuracy and lower detection limit than the external standard method.The contents of 16 rare earth elements in chicken,prawn and pork samples in Changchun high tech Zone were determined by ICP-MS internal standard method.The results can provide data support for the relevant departments to formulate the limit standards of rare earth elements in meat products... |
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