Estradiol Radioimmunoassay - Problems with extraction (May/26/2005 )

Have been trying to extract bovine plasma samples with ethyl acetate for a radioimmunoassay with lots of problems. Unlike our control samples which extract fine and are consistent, these samples have been forming a gel consistency when add the ethly acetate and tinting the acetate yellow. Does anyone know why this may be occurring? We suspect that something in the plasma is reacting with the ethyl acetate thus affecting the assay. Any suggestions would be greatly appreciated.