ANATECH makes the buffer salts kits for re-assaying and buffering formalin
out of the distillation process.   sharon osborn
-----Original Message-----
From: J. A. Kiernan <jkiernan@julian.uwo.ca>
To: RSRICHMOND@aol.com <RSRICHMOND@aol.com>
Cc: histonet@pathology.swmed.edu <histonet@pathology.swmed.edu>
Date: Friday, September 03, 1999 7:26 AM
Subject: Re: Formaldehyde recycler & assaying


>On Thu, 2 Sep 1999 RSRICHMOND@aol.com wrote:
>
>> I have no experience with the formaldehyde still, and that's what I'd
like to
>> know more about. In my experience, assaying the formaldehyde and mixing
the
>> buffer salts would be beyond the skills of most laboratories (I NEVER saw
a
>> lab prepare neutral buffered formalin correctly). The only way I can
imagine
>> this being practical is with kits of pre-mixed buffer phosphates, and
I've
>> been surprised that nobody ever made these available. Are they available
now?
>
>   If you're really keen on having a physiologically buffered and isotonic
>   phosphate solution, then Dulbecco's balanced salt solution is the one
>   to go for: kind to cultured cells and doesn't need a CO2-enriched
>   atmosphere to maintain its pH. It is, in fact, PBS with cell-friendly
>   amounts of potassium, calcium and magnesium ions. It's fairly easily
>   made by weighing and dissolving 6 cheap ingredients, but even more
>   easily generated by chucking a little pot of pre-mixed Dulbecco powder
>   into a litre of distilled water. Several companies sell the little
>   pots of powder. It costs more but saves time, and there is nothing
>   secret about what you're buying in the kit, so it's OK to use it in
>   research. The recipe was published in 1954: J. Exp. Med. 99, 167-182.
>   (This popular solution is a by-product of an otherwise largely
>   forgotten publication.)
>
>   Assaying the recovered formaldehyde should not be necessary for most
>   purposes because the concentration of this compound in a fixative
>   solution is not at all critical. The concentration of monomeric
>   methylene glycol and low polymers (active in fixation) increases
>   with the dilution. Consequently it's possible to use neat formalin
>   (37-40% HCHO) or a 1:100 dilution (0.4% HCHO) without changing the
>   chemical reactivity with proteins. It's always necessary to allow
>   enough time for formaldehyde fixation (a few days, at least) and
>   the much shorter times currently used in routine histopathology
>   produce tissues fixed only partly by formaldehyde and mostly by the
>   coagulative action of the solvents used for dehydration.
>   For everything you could ever want to know about formaldehyde,
>   see the book, "Formaldehyde" by JF Walker. 3rd edn, 1964, Reinhold,
>   New York.
>
> John A. Kiernan,
> Department of Anatomy & Cell Biology,
> The University of Western Ontario,
> LONDON,  Canada  N6A 5C1
>
>
>