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The purpose of this study is to develop and validate a screening assay for ractopamine in exotic hog tissues that are not utilized as food material in the U.S. but are highly utilized in Chinese cultures or closely related to these cultures. <P>These assays would provide assurance that ractopamine concentrations in these tissues were low enough to not be any threat to the consumer, thereby opening new markets for U.S. products currently being denied because of the use of ractopamine in hog production in the U. S.
Approach: The use of an ELISA-based ractopamine assay for screening in urine as well as commonly used food tissues has been validated and is currently in commercial practice. As is well established, the use of ELISA for tissues must be individually tested and validated and generally requires preliminary purification to eliminated sample matrix effects that would otherwise interfere with the analysis. We will utilize solid phase extraction procedures adapted from previous experience prior to utilizing the ELISA procedure. Tissues and dry ice will be homogenized and the dry ice sublimed. The tissue will be extracted and solvent evaporated, the solution reconstituted with an appropriate buffer and utilized directly for the ELISA procedure. If needed, tissue extract will be applied to solid phase extraction cartridge for additional cleanup prior to ELISA analysis. Comparison of the standard curve with one from buffer will demonstrate if the matrix effect of the tissue has been reduced sufficiently for analysis. The determination will be carried out on a number of incurred samples and those showing positive ELISA analysis will be verified using an alternate instrumental procedure such as LC-MS/MS.