Reusable fiber optic immunosensor for rapid detection of imazethapyr herbicide

• Published in: Journal of agricultural and food chemistry Vol. 41; no. 5; pp. 843 - 848
• Main Authors: Anis, Nabil A, Eldefrawi, Mohyee E, Wong, Rosie B
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.05.1993
• Subjects: Biological and medical sciences; Biosensors; Biotechnology; Fundamental and applied biological sciences. Psychology; Methods. Procedures. Technologies; Various methods and equipments; Performance evaluation; Soils; Antibody; Quartz fiber; Fluorescent labelling; Biosensor; Immobilization; Detection; Herbicide; Optical fiber; Immunological method
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf00029a031

Imazethapyr is the active ingredient of PURSUIT herbicide. This herbicide belongs to the imidazolinone class of compounds. Polyclonal antibodies have been prepared in rabbits and sheep which specifically recognize this class of compounds. Using immune sera, ELISAs have been developed for imazaquin, imazapyr, imazethapyr, and imazmethabenz methyl (the active ingredient for SCEPTER, ARSENAL, PURSUIT, and ASSERT herbicides, respectively) with sensitivity at low nanogram per milliliter levels. The quantitation of imidazolinones in soil requires a certain amount of sample pretreatment, thus, the throughput is not ideal. A simpler immunoassay method for screening large amounts of soil samples economically would be useful. Using the same polyclonal antibody, fluorescent immunoassay employing optical fiber and fluorescence was developed to assay for imazethapyr. Purified sheep antibody was immobilized on quartz fibers. A mixture of fluorescein-labeled imazethapyr analog and free imazethapyr was presented to the fiber for direct competition of the antibody binding sites or displacement of a previously bound fluoresceinated imazethapyr analog on the surface of the fiber. The response time for the detection of imazethapyr ranged from seconds to minutes. The sensitivity of the assay was 1 nM (0.3 ng/mL). This binding of the fluorochrome to the fiber was reversible by washing with a phosphate buffer saline. Multiple measurements were easily processed with a single fiber over the course of several hours. Analysis of imazethapyr residue in soil can be accomplished by subjecting a clarified soil extract solution directly for analysis without further treatment. The cross-reactivity data indicated that the assay is apparently specific for the imidazolinone class of compounds.