I'm with a laboratory microwave vendor:
Never mind 74˚ C - some microwave protocols call for temperatures as=20
high as 82˚ or 84˚ C (!) in order to exceed the boiling point of
isopropanol, facilitating its replacement with paraffin. Naturally, this
caused some concern and resistance in the anatomic pathology community.
However, look at your own question about IHC: when you consider antigen
retrieval protocols call for 100˚C, even 84˚ pales by comparison. Of
course, there are many reasons you want to minimize the amount of time
spent at high temperatures, but there is no problem with the majority of
tissue types for the relatively short timeframes involved in microwave
Also, by the paraffin step, the tissue has already been fixed,
dehydrated, and defatted; while it is in a sense still "tissue," it's
radically different from the tissue as received. You certainly don’t
want to burn or "cook" anything, but 82°C isn’t really extreme in this
context. (I'd be at least as concerned about how a given paraffin and
additives hold up at high temperatures, so it's always a good idea to
check with the manufacturer.) There also is the issue of vacuum; since
the purpose of high temperature is to get above the boiling point of
isopropanol, and vacuum causes BP depression, vacuum should allow you to
lower the temperature to something you're more comfortable with.
More information may be found at
Very best regards,
Microwave Product Manager
Energy Beam Sciences, Inc.
29-B Kripes Rd.
East Granby, CT 06026
Tel: 800.992.9037 x 341
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- Mahatma Gandhi
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Gudrun Lang wrote:
> I've seen a protocol for isopropanol-processing with an IPA-temperature
> about 74 degrees. That is near the boilingpoint and means rather a boiling
> out of the tissue than acting as intermedium. Similar protocols are found
> with the microwave-techniques. I think there is no principal difference in
> reaching the temperature.
> What I'm a little confused about is the fact, that usually recommended
> temperatures for tissueprocessing don't raise above 62 degrees. So how does
> this influence staining, ihc-staining etc.?
> What are the temperatures in your protocol?
> What does the community think about this issue?
> Gudrun Lang
> Biomed. Analytikerin
> Akh Linz
> Krankenhausstr. 9
> 4020 Linz
> -----Ursprüngliche Nachricht-----
> Von: email@example.com
> [mailto:firstname.lastname@example.org] Im Auftrag von Judy
> Gesendet: Montag, 02. April 2007 15:53
> An: email@example.com
> Betreff: [Histonet] Peloris Processor
> We have the Peloris rapid tissue processor. It is xylene free but does
> not use microwaves. It uses isopropyl alcohol after the reagent alcohol
> to remove all traces of water and then goes straight to the paraffin
> >from there. Amazingly, and contrary to everything we have been taught,
> this works!
> It processes small biopsies in approximately 1 hour. Shave biopsies
> take approximately 2 hours and the larger specimens 4 to 6 hours. We
> find the processing to be at least equal to routine processing and in
> many cases, superior to it. Because it does not use xylene, the tissues
> are not hard and brittle as they can sometimes be with routine
> It has two separate retorts which can run two separate runs at the same
> time. We are able to process our specimens throughout the day instead
> of everything being processed at night as in the past. It has greatly
> improved our TAT.
> The Peloris tracks the number of blocks run and, based on this, tells
> you when to change the various solutions. As a result, we have saved a
> significant amount of money on reagents.
> We are extremely happy with ours.
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