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 occurr ing soil bacterium and is effective on several classes of insects, especial ly Lepidopteran larvae. Spinosad is registered in many countries for use on a variety of crops, including cotton, corn, soybeans, fruits, and vegetabl es. Residue methods utilizing a magnetic particle-based immunoassay (IA) te st kit have been developed and validated for determining spinosad in enviro nmental; and food matrices. These methods involve an extraction of the resi dues from the matrices with appropriate solvents. For some matrices, the sa mple extracts can be diluted and measured directly by IA without any cleanu p. For other matrices, sample extracts are purified using liquid-liquid par titioning and/or solid phase extraction prior to measurement by IA. The met hods determine the total residue of spinosad, which includes the active ing redients (spinosyns A and D) and several minor metabolites, including spino syn B, spinosyn K, and N-demethylspinosyn D. The methods have validated lim its of quantitation of 0.0001 mug/mL in water, 0.05 mug/g in sediment, and 0.010 mug/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.