Determination of spinosad and its metabolites in food and environmental matrices. 3. Immunoassay methods.

Spinosad is an insect control agent that is derived from a naturally occurring soil bacterium and is effective on several classes of insects, especially Lepidopteran larvae. Spinosad is registered in many countries for use on a variety of crops, including cotton, corn, soybeans, fruits, and vegetables. Residue methods utilizing a magnetic particle-based immunoassay (IA) test kit have been developed and validated for determining spinosad in environmental and food matrices. These methods involve an extraction of the residues from the matrices with appropriate solvents. For some matrices, the sample extracts can be diluted and measured directly by IA without any cleanup. For other matrices, sample extracts are purified using liquid-liquid partitioning and/or solid phase extraction prior to measurement by IA. The methods determine the total residue of spinosad, which includes the active ingredients (spinosyns A and D) and several minor metabolites, including spinosyn B, spinosyn K, and N-demethylspinosyn D. The methods have validated limits of quantitation of 0.0001 microgram/mL in water, 0.05 microgram/g in sediment, and 0.010 microgram/g in crops, crop processed commodities, and animal tissues. This paper briefly summarizes the residue methodology and method validation data for spinosad in 34 food, feed, and environmental matrices.