Development of a portable field immunoassay for the detection of aflatoxinM-1 in milk

Many methods for AFM(1) detection exist, but most are time consuming, emplo y expensive equipment and require experienced personnel. To overcome these problems a membrane-based flow-through enzyme immunoassay has been develope d (patent pending). The assay comprised a nylon Immunodyne ABC membrane spo tted with anti-mouse antibodies, a plastic snap-fit device, absorbent cotto n wool, mouse anti-AFM(1) monoclonal antibodies (Mab), and AFB(1)-horseradi sh peroxidase (HRP) conjugate. This assay was coupled to an immunoaffinity column (IAC). The visual detection limit was 0.05 ng/g AFM(1) in milk. Assa y time for IAC clean-up was 12 min, and that for the flow-through assay was 18 min, hence the total assay time was 30 min. This method allows for a ra pid screening of milk consignments which do not conform to the maximum perm issible limits of 0.05 ng/g AFM(1), hence enabling the rejection of such at the farm level. Laboratory validation was done using certified reference m aterials (CRM) with AFM(1) concentrations of < 0.05, 0.09 and 0.76 ng/g. Pr ecision of the assay was high as shown by the high repeatability of the ass ay results. There were no significant differences in recoveries between sta ndard in buffer and CRM (P > 0.05), and assay responses for these two were highly correlated (99.63%). (C) 1999 Elsevier Science B.V. All rights reser ved.