Development and characterization of immunoaffinity columns for the selective extraction of a new developmental pesticide: Thifluzamide, from peanuts Original Research Article

The registration of new pesticides requires sensitive and reliable assay methods to determine the distribution of pesticide residues and their corresponding metabolites in soil and crop extracts. We have prepared specific columns to selectively extract a new developmental pesticide: Thifluzamide, from peanut samples. Antibodies generated against the target analyte were covalently immobilized on a silica-based solid support and were evaluated for the selective extraction of the parent compound using high performance liquid chromatography. The specificity of the antibodies was demonstrated as interferents of similar polarity were selectively removed from percolated samples. A simple elution protocol, involving only 4 ml of methanol/water (80/20) was shown to be efficient in recovering 100% of retained parent compound from percolated standard solutions. Such columns could be re-used for more than 10 times with no significant alteration in capacity or elution profile. Column to column reproducibility was also investigated and demonstrated the reliability of the column preparation procedure. Applied to peanut extracts, these columns allowed the development of a simple clean-up procedure consisting of two steps. Sample extracts were first de-fatted before application on the immunoaffinity cartridges. Two different types of cartridges were assayed based on two different solid support materials. Clean chromatograms allowed the quantification of the target analyte in the extracts. Recoveries averaged 77% (n=5, R.S.D.=14%) for the clean-up procedure and proved the usefulness of this technique in the isolation and purification of this new pesticide in a typical registration study.