The first monoclonal antibody-based, matrix-resistant immunoassay for the carbamate herbicideasulam, in water

Abstract

To date, no ligand binding assay has been described for the carbamate herbicide asulam, although a variety of physical methods, dependent on pre-concentration of water samples, have been documented for its assessment. However, asulam is increasingly used in sensitive agricultural areas, and statutory regulations concerning its monitoring will undoubtedly become more stringent. Antibodies are optimal partners in ligand binding assays, but it is commonly understood by immunological researchers that where no antibody reactive with a particular antigen has yet been described, the immunogenicity of the antigen may be particularly restricted. By the expedient of employing a specialised approach to final immunisation with an asulam–protein conjugate, prior to the immortalisation of a specific anti-asulam antibody-producing cell, we have succeeded in generating a monoclonal antibody reactive specifically with asulam that can be configured in a convenient immunoassay. This antibody may be used flexibly in a number of ways: small sample volumes of 10 µl can be assessed to sensitivities of 4.35 × 10⁻⁷ M (10 µg L⁻¹) while avoiding discrepancies contributed by the assay matrix; this antibody-based assay can also be formatted to deliver sensitivities at levels stipulated by regulatory authorities (e.g., 4.35 × 10⁻⁹ M or 0.1 µg L⁻¹) directly from a water sample, without prior pre-concentration.