Sulfadiazine (SD), one kind of broad-spectrum antibiotic, is effective for anim al production for its excellent antibacterial and pharmacokinetic properties . It has been widely used in different lines of poultry, cattle, agriculture and beekeeping. However, Sulfadiazine is prohibited in m os t countries as its residue may cause serious side effects , such as hematotoxic. Therefore, it is possible that Sulfadiazine residues , after use in illegal practice, may lead to a ris k for consumers .
PRINCIPLE OF THE TEST
Competitive assays are primarily used for testing small molecules . If Sulfadiazine is present in the sample it will therefore bind with the conjugate and will be labelled. As the sample migrates along the membrane and reaches the capture zone an excess of labelled antibody will bind to the immobilis ed antigen so that no visible line is produced. The bound conjugate will then bind to the antibodies in the control zone producing a vis ible control line. A single control line on the mem brane is a positive result. Two visible lines in the capture and control zones is a negative res ult. However, if an excess of unlabelled Sulfadiazine is not present, a weak line m ay be produced in the capture zone, indicating an inconclusive result.