Detection of sulfamethazine in water, milk and pig manure by dipstick immunoassay

During the past few years, there has been an increasing interest in rapid visual tests that could be performed outside the laboratory, for example on farms, in store houses or in food production plants. Hence, cost effective and simple screening methods are required for residual analysis of environmental and food samples on-site. Here, a simple and instrumental independent dipstick immunoassay for sulfamethazine detection is described. The polyclonal antibody was optimised in terms of coating dilution on a nitrocellulose membrane, dilution of peroxidase tracer conjugate, blocking agents and incubation times. Test results assessed by visual measurement can be available within 20 minutes. In buffer, water, skimmed milk and pig manure extract, sulfamethazine fortified at 50 and 100 µg/l has exhibited clear visual differentiation in colour development (lower intensity) in comparison to the control spot intensity (high intensity) of the dipstick.