I have problems with my p24 ELISA. Backgrounds higher than some standard readings leading to negative values in some standards and some values completely out of range.
The High protein binding plates, wouldn't they increase the background instead? They may instead bind a lot of the secondary antibody? Can you give me some details?
I would like to advice to use buffer with casein (milk without fat) and mertiolat. You can make own buffer or buy (Sigma or other company)? sometimes I used BSA but only V fraction.