Dr. Grabsch:

What you are observing is some of the metachromatic characteristics of DAB.
A very common phenomenon.  It can be a function of concentration, incubation
time, etc.  There are publications on this issue, but the exact reference
citations are not immediately available to me at this time.

Regards,
Peter
-
Peter A. Takes, Ph.D., RAC
Director, Clinical & Regulatory Affairs
STEREOTAXIS, Inc.
Ph. 1-314-615-6964; Pager: 841-9351
ptakes@stereotaxis.wustl.edu

Heike Grabsch wrote:

> We use DAB as chromogen in ICC-studies. At the moment I am wondering why
> we get do different shades of coulours from almost black, pale very nasty
> looking dark brown to bright orange-brown.
> I do not like it, I would like to have the same nice brilliant colour
> every day. Are there any ideas about may be the chemical process behind
> this. Is it a matter of concentration (which is the same always) or
> temperature or what.
> Any comments and help to get a reproducible nice brilliant colour are
> highly appreciated.
>
> Dr. Heike Grabsch, Germany



-