title: 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.
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 microg 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 microg kg(-1) in liver and 2 microg 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 microg kg(-1)).
authors.affiliation: Key Laboratory of Food Nutrition and Safety, Ministry of Education, Tianjin University of Science and Technology, Tianjin, 300222, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Shuo
authors.initials: S
authors.lastname: Wang
authors.forename: Jiayi
authors.initials: J
authors.lastname: Zhang
authors.forename: Junwei
authors.initials: J
authors.lastname: Liu
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004531:Eggs / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay / Q000295:instrumentation* / Q000379:methods*; D005399:Fishes; D005504:Food Analysis; D017979:Gold Colloid / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008460:Meat / Q000032:analysis; D008892:Milk / Q000737:chemistry; D015394:Molecular Structure; D009994:Osmolar Concentration; D012680:Sensitivity and Specificity; D013418:Sulfamethazine / Q000032:analysis* / Q000737:chemistry
chemical_list: D017979:Gold Colloid; D013418:Sulfamethazine