Sandwich ELISA-insulin detection - (Apr/22/2007 )

Hi to all,
I am working on sandwich ELISA for insulin detecion in serum, we have taken recombinant Human insulin (sigma grade) for immunization and prepared monoconal antibodies...we have staderdized cELISA and found out the pair of antibodies which can used for sandwich ELISA. we sandwich ELISA was performed the monoclonal antibodies are detecting the recombinat human insulin but we as Antigen source we added as serum the sandwich is not working...can any one help me out here..as it is a veryu crucial stage now...

i'm also looking for Sandwich ELISA- GFP detection kit but not sure where to go about looking for it...