Application of Empore Disk Extraction for Trace Analysis of Spinosad and Metabolites in Leafy Vegetables, Peppers, and Tomatoes by High-Performance Liquid Chromatography with Ultraviolet Detection

Residue methods were developed for the quantitation of spinosad and metabolites in leafy vegetables, peppers, and tomatoes. The compounds were extracted with a solution of acetonitrile/water. The extract was purified and concentrated by C 18 Empore disk extraction, followed by silica and cyclohexyl solid-phase extraction. All five analytes in the purified extract were determined simultaneously by reversed-phase high-performance liquid chromatography with ultraviolet detection. For all analytes in six different commodities, the average recoveries ranged from 77 to 97% with standard deviations ranging from 2 to 7%. The limits of quantitation and detection were 0.01 and 0.003 μg/g, respectively. These results compare favorably with those obtained by replacing the Empore disk extraction with liquid−liquid partitioning in the method. Analysis of cabbages sprayed with [ 14 C]spinosyn A from a residue study indicated that the Empore disk extraction provided a cleaner final extract. Confirmation of analytes was performed by using liquid chromatography/mass spectrometry.