Enzyme-linked immunosorbent assay and colloidal gold immunoassay for sulphamethazine residues in edible animal foods: investigation of the effects of the analytical conditions and the sample matrix on assay performance |
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Authors: | Lei Wang Shuo Wang Jiayi Zhang Junwei Liu Yan Zhang |
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Institution: | (1) Key Laboratory of Food Nutrition and Safety, Ministry of Education, Tianjin Key Laboratory of Food Nutrition and Safety, Tianjin University of Science and Technology, Tianjin, 300222, China |
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Abstract: | To determine sulphamethazine (SMZ) residues in edible animal foods (pig muscle, chicken muscle, egg, fish, milk and liver),
a competitive direct enzyme-linked immunosorbent assay (ELISA) and a colloidal gold immunoassay were established. The limits
of detection of the ELISA and the colloidal gold immunoassay were 0.02 and 0.5 μg kg−1, respectively. The specificity of the ELISA developed to the SMZ was high according to the results of cross-reactivity testing
with 14 kinds of sulphonamides. To obtain a more sensitive immunoassay, buffer solution (30 mmol L−1 phosphate-buffered saline with 0.05% Tween 20, pH 8.5) was optimized through the whole test procedure. A simple and efficient
extraction method for the rapid detection of SMZ residues in foods was developed, with recoveries between 74 and 117.5%. Matrix
effects can be avoided by 1:10 dilution of pig muscle, chicken muscle, egg, fish, milk and liver with optimal buffer. The
detection limit of SMZ was 5 μg kg−1 in liver and 2 μg kg−1 in the other five samples. For the validation of the ELISA tests, sample extracts were analysed by ELISA and high-performance
liquid chromatography. The results obtained by these two methods showed a good correlation (r
2) which was greater than 0.9. The colloidal gold immunoassay presented in this assay was successfully applied to determine
SMZ in pig muscle, milk and fish below or equal to the maximum residue level (20 μg kg−1). |
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Keywords: | Sulphamethazine ELISA Colloidal gold immunoassay Food Matrix effect |
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