Haltbarkeit von Paraformaldehyd

Dr Engelbert Buxbaum engelbert_buxbaum at hotmail.com
Fri Aug 12 10:29:10 EST 2005


alexunm at web.de wrote:

> Warum sollte man Paraformaldehydlösung nur wenige Tage zum fixieren
> von Zellen/Gewebe verwenden ?
> Ich habe leider keine validen Zahlen zur Haltbarkeit gefunden, immer
> nur Berichte, das es nur wenige Tage verwendbar ist, aber nirgends
> warum.
> Wer kann mir helfen ?
> 

The question is about the storage time of paraformaldehyde solutions.

This is an international group, and your chances of getting an answer
are much higher if you use English.

Fixing tissue is done by formaldehyde (methanal, HCHO). This substance
can polymerise into paraformaldehyde, a solid of low water-solubility.
Preparing the formaldehyde solution from paraformaldehyde results in a
solution of known strength, but within a few days some of the
formaldehyde will have polymerised again into the ineffective
paraformaldehyde. Thus you no longer know the concentration of active
ingredient, making fixation results somewhat unpredictable.

By the way this polymerisation process is accelerated at low
temperature, thus formaldehyde solutions should be stored at room
temperature, protected from light and in air-tight bottles.


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