Development Of Gold Immunochromatographic Assay For Rapid Detection Of Sulfamerthoxazole Residues In Milk

A gold immunochromatographic assay (GICA) was applied to testing sample for residues of the antimicrobial Sulfamethoxazole (SMZ). In order to establish a one step strip test for the detection of Sulfamerthoxazole residues, polyclonal anti-sulfamethoxazole antibodies were purified by caprylic acid ammonium sulphate method. Tri-sodium citrate with aqueous gold chloride were mixed to make 20nm gold sol which were coupled with the polyclonal antibodies after identification. The conjugation solidified to glass fibers, SMZ-OVA was immobilised on nitrocellose membrane to prepare for kit.The various factors and conditions of the immunochromatographic lateral-flow assay were explored, and the optimal reaction conditions of the assay were ascertained. A GICA for rapid detection of Sulfamerthoxazole residues in milk was successfully established. The GICA device had a cut-off value of 100ng/ml for detecting the SMZ dissolved in the phosphate balanced solutionhad and in milk. Cross-reaction assay showed that the cross-reaction was occurred when milk was fortified with SN, SM₂ to 250ng/mL and when the concentration of SN,SM₂, SD, SMP, SMM, SQ, SDM is 100ng/mL there was no cross-reaction. The device had a high quality in repetition and the storage life was 90 days.The major advantages of GICA were that results could be obtained within 10min and that all needed reagents were included in the device. The test device could be used to detect the Sulfamerthoxazole residue in fresh cow milk. The method producing GICA for SMZ could be used for reference in the development of the detection of other veterinary drugs.