Problem with ELISAs

[mark]

Robin Blumenthal wrote:
> 
> We are having an interesting problem in our lab with our ELISAs. I was
> wondering if anyone out there might have any ideas.
> 
> We are doing sandwich ELISAs for cytokines and Igs (both human and murine)
> using a biotin-linked secondary Ab, strep-HRP and OPD as a substrate.  The
> problem we are having is that the developing has slowed down incredibly.
> Assays that once took 5 min to develop are now taking over 30 min and
> still not coming all the way up.  We are in the process of testing all the
> components but in a latest test two different batches of HRP-strep gave
> the same results.  We are a bit stumped.....anyone have any ideas?
> 
> We would appreciate any ideas!
> 
> Thank you
> 
> --
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Robin Blumenthal, Ph.D.
> Department of Pediatrics, Rm S303
> Stanford University
> 300 Pasteur Drive
> Stanford, California 94305
> 
> robinb at leland.stanford.edu
> (650) 723-8224    (650) 498-4632 FAX
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


My first guess is PH