Re: [Histonet] paraformaldehyde in the microwave

From:Michael Doube

Thanks for your reply John.

I am aware that certain tissue prep protocols are substantitally 
accelerated by microwave radiation independent of a direct thermal 
effect, so my question was more to discover whether a similar 
acceleration effect might operate duing simple chemical preparation.  
This is based on the chance observation that a few minutes on low, with 
the PFA suspension in a flask in a large water bath was sufficient to 
make my PFA depolymerise.

Thanks to all those concerned about fume safety, yes we are fume hooded 
and well ventilated (to a fault, actually) and I seal the top of my flask.


John Kiernan wrote:

>The source of heat does not matter.
>Paraformaldehyde depolymerizes at 60C in the
>presence of a base such as disodium hydrogen
>phosphate. It won't depolymerize ("dissolve") when
>heated in pure water. 
>This information is present in every
>histotechnical textbook published since about
>1960. The chemistry is very simple, and abundantly
>available on the internet. Paraformaldehyde and
>formalin are sources of hydrated formaldehyde,
>which fixes tissues well if used at approximately
>neutral pH for 12-24 hours.
>John Kiernan
>London, Canada.
>Michael Doube wrote:
>>Hi there
>>It's been a while since I last made 4% paraformaldehyde in
>>phosphate-buffered saline - it was a few years back as an undergrad.
>>This time I'm in a new lab, and found that there is no hotplate!  So,
>>after trying to keep the suspension warm with hot water baths (tedious)
>>, I resorted to the microwave, on low power.  It seems to work much
>>faster than what I remember with the conventional technique.  Has anyone
>>had any experience with this?
>>Michael Doube  BPhil BVSc MRCVS
>>MPhil / PhD Student
>>Dental Institute
>>Barts and The London School of Medicine and Dentistry
>>Queen Mary, University of London
>>New Rd
>>London  E1 1BB
>>United Kingdom
>>Phone +44 (0)20 7377 7000 ext 2681

Michael Doube  BPhil BVSc MRCVS
MPhil / PhD Student
Dental Institute
Barts and The London School of Medicine and Dentistry
Queen Mary, University of London
New Rd
London  E1 1BB
United Kingdom

Phone +44 (0)20 7377 7000 ext 2681

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