Rapid Detection of Three Pesticide Residues in Vegetables Using Colloidal Gold Immunoassay
Rapid test strips for the detection of imidacloprid,profenofos and carbofuran were developed based on colloidal gold immunochromatography,and its application effect in the detection of garlic and cabbage was evaluated.The test strips for rapid detection of imidacloprid,profenofos and carbofuran were established by preparation of colloidal gold by reduction with trisodium citrate,with the monoclonal antibodies of imidacloprid,profenofos and carbofuran labeled with colloidal gold particles as the detection probes,nitrocellulose membrane as the solid-phase carrier,imidacloprid-BSA,profenofos-BSA and carbofuran-BSA conjugate as the detection lines,and goat anti-mouse IgG antibody as the control line.The parameter conditions,including gold-labeled antibody usage,concentrations of antibody for labeling,and concentration of the coating antigen were optimized.Under the optimal condition,the sensitivity,specificity and stability,as well as the accuracy of the test strips were evaluated.With optimization of sample extraction,the test strips were employed for the detection of pesticides in two vegetable samples by negative detection and addition of standardized pesticide products.The results showed that in the optimized process parameters,the concentrations of colloidal gold labeled antibody of imidacloprid,profenofos and carbofuran were 9.6,8.4,9.6 μg/mL,respectively,the concentrations of the antigens coated were all 0.3 mg/mL,and the detection time was about 15 min.The limits of detection of imidacloprid,profenofos and carbofuran were 20,3 000,and 20 ng/mL,which were in compliance with the limits of the national standard for the two kinds of vegetables.There was no cross-reactivity and good specificity in the detection of other drugs with similar function and structure as imidacloprid,profenofos and carbofuran.The most suitable extractants for carbofuran and imidacloprid pesticides were 4 mL of ethyl acetate and 4 mL of methanol,respectively,with a sample size of 2 g and a supernatant of 3 mL;for profenofos pesticide,the most suitable extractant was 9 mL of ethyl acetate,with a sample size of 3 g and a supernatant of 8 mL,and the supernatant was dried with nitrogen gas.The detection results of 50 negative and spiked samples of vegetables showed a false positive rate of 6%and a false negative rate of 0.It can be seen that the developed test strips are suitable for on-site rapid detection of garlic and cabbage as well as screening of a large number of samples in grass-roots laboratories,and can provide an effective regulatory tool for the control of pesticide residues in garlic and cabbage.
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