Homogeneous enzyme immunoassay for pyrethroid pesticides and their derivatives using bacillary alpha-amylase as label

A new enzyme immunoassay for detection of some pyrethroid pesticides (permethrin, phenothrin) and their derivatives containing 3-phenoxybenzoic group has been developed. It is based on enzyme multiplied immunoassay technique (EMIT), modulation of catalytic activity of hapten-enzyme conjugate by anti-hapten antibodies and restoring the initial activity level by free hapten in the sample tested. Alpha-amylase from Bacillus subtilis is proposed as a new enzyme label for EMIT. Inhibition of the 3-phenoxybenzoic acid-amylase conjugate by specific antibodies was revealed at the systems detecting nonsplinted starch or released aldehyde groups. EMIT conditions for pyrethroid pesticides and their derivatives have been optimized. The assay time is not more than 45 min, the detection limits reach 2–5 ng ml−1. Photometric measurements can be carried out by means of standard ELISA equipment. The proposed label was also used to develop EMIT for pesticide 2,4dichlorophenoxyacetic acid.