| Ractopamine is a kind of synthetic drug which has phenethanolamines basic structure. It can increase the ratio of lean to fat, enhance the feed conversion efficiency and improve the muscular mass by inhibiting the synthesis of fat. However, if a large amount of ractopamine is ingested, it’s difficult for animal to expel it from the body through the metabolism, which will make the residual ractopamine in animal products exceed the standard. People that intake ractopamine through the food chain will appear muscle vibration, headache, palpitation, nausea, tremble, vomiting and other adverse symptoms, as a result, the health would be impaired severely. Therefore, it is very important to establish an accurate and rapid detection method of the ractopamine residues in animal products. This paper set up three methods for rapid detection of ractopamine and main researches are as follows.1. Visual detection of ractopamine based on aptamer-colloidal goldThe effects of NaCl electrolyte concentration, incubation time, incubation temperature, and pH of the solution on the experiment were investigated under the condition of the optimum aptamer concentration of 5 μmol/mL. The detection limit of ractopamine reached 10 ng/m L, the linear range was 10~400 ng/mL, and the correlation coefficient R2 was 0.997 under the optimized experimental conditions. For the detection of mixed feed, it has been found that the detection line reached 10 ng/mL, the linear range was 10~400 ng/m L with the linear correlation coefficient R2 of 0.973 and the average recovery was from 79.4% to 121.1%. And the relative standard deviation(RSD) is 0.415 to 4.475% to retest 5 times. In addition, no cross reaction happened for ractopamine with SAL and CL.2. Determination of ractopamine based on aptamer composite film electrochemical immunosensorA RAC aptamer electrochemical immunosensor based on multi wall carbon nano tubes, L-arginine, gold nano particles and ractopamine aptamer modified by amino has been prepared successfully. Some factors such as scanning speed, incubation temperature, incubation time, the modified amount of adapter and pH were investigated. The results indicated that the sensor showed not only low detection limit but also good selectivity. Under the optimum conditions, the linear range was from 1.00×10-11 to 1.00×10-6 mo L/L with the linearity relation coefficient of 0.9804 and the detection limit reached 1.00×10-11 mol/L. Furthermore, the sensor was of the simple operation and stable performance when it was applied into the determination of ractopamine in swine urine, where the recovery of ractopamine spiked in swine urine was from 97.1% to 103.0%, and the relative standard deviations were below 9.4%.3. Determination of RAC based on sulfydryl modified aptamer electrochemical immunosensorA new electrochemical sensor based on ractopamine aptamer with sulfhydryl group has been prepared, where the glass carbon electrode was modified by using PDDA-GNs and gold nano particles to get a AuNPs/P-L-Arg/MWCNTs/GCE electrode. And the ractopamine aptamer with sulfydryl was immobilized on the surface of the modified electrode by self-assembly function. Some factors such as scanning speed, incubation temperature, incubation time, the modified amount of adapter and pH were investigated. The results indicated that the linear range of the electrochemical sensor was from 1.00×10-12 to 1.00×10-7 mol/L with the linearity relation coefficient of 0.996. And the detection limit of the sensor reached 1.00×10-12 mol/L. Moreover, the sensor was of the good selectivity and simple operation as well as the stable performance when it was applied into the determination of ractopamine in swine urine, where the recovery of ractopamine spiked in swine urine was from 96.4% to 104.0%, and the relative standard deviations were below 9.1%. |
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