Sorry, if this has been posted already.  I can't tell because I'm getting a
delivery failure.
---------------------- Forwarded by Rande Kline/EMI/Merck on 08/11/99 10:21
AM ---------------------------


Rande Kline
08/11/99 09:34 AM

To:   "William E. James Jr. H.T. A.S.C.P." <w.e.jmesjr.@worldnet.att.net>
cc:   HistoNet <histonet@pathology.swmed.edu>
Subject:  Re: reagents  (Document link not converted)

I've used dyes that had been around for many years without any problems.
Some dyes do get better with age.  But here's what can happen.

I'll use giemsa stain as an an example.  When making dry giemsa powder an
oxidizer is added to the methylene blue to promote oxidation and activate
the staining power of methylene blue.  It is the oxidation that produces
the good staining quality and with time causes the staining quality to
deteriorate.  Eosin is added to the solution and allowed to precipitate
into the dry stain form.  As a dry powder, oxidation is often promoted by
minute quanitities of trapped oxidizer brought over in the process in
combination with natural oxidation promoted by other impurities.  The stain
continues to go through the  oxidation cycle and will improve with age, but
than it kind of peaks out and loses staining quality. The final peak could
take years.  This would be true for any dry powder produced with an
oxidation step (hematoxylin is another example.)

Be careful with any chemicals and check the decompostition information made
available in the MSDS when determining shelf life.  In the April, 1999
edition of Laboratory Medicine, I wrote an answer for the Q&A section on
expiration of bulk chemicals.  I would also apply this information to dry
stains.

As mentioned in many of the replies, you can always run a control to insure
staining quality.

Rande Kline HT (ASCP)
Technical Services
EM Science



"William E. James Jr. H.T. A.S.C.P." <w.e.jmesjr.@worldnet.att.net> on
08/08/99 09:22:53 PM

To:   HistoNet <histonet@pathology.swmed.edu>
cc:
Subject:  reagents




Hello,
        I am looking for any info on the shelf life of reagents in dry
form.
ie: Eosin y, Hematoxylin, Congo Red, etc.

        Will they last for more than 10-15 years and is there any way to
test
them for use.

        I just started in the lab here at AML in Louisiana and the
reagents
here date back to 85 and in most cases none are less than 8 yeas old.
                                                        thanx
                                                W.E.James Jr. H.T.