Bouins and picric acid

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From:Gayle Callis <> (by way of Marvin Hanna)
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I believe the importance of the Bouins, with the acetic and picric acid
components, is to acidify the tissues, in order to make the dyes penetrate
correctly.  John Kiernan will help on this.

The publication in J of Histotechnology, Citrate buffer alternative to
picric acid for Masson trichrome stain, v 10 (4), Dec 1996 by Joyce Moore
gives details.

It is a 0.1M citrate buffer, pH 5.9 to 6.0, microwaved for 1 min. I would
think the important factor in this solution is that the pH of the buffer
matches that of Bouins, would be a good thing to check, and try.  Another
factor, this buffer probably prevents swelling of tissues, a problem with
acetic acid and picric acid alone, and a reason why it is combined with

I have not tried this, but did keep the article on the chance picric acid
might be banned from my lab. So far that has not happened, but storage is
done carefully, under water.  We only use saturated solutions anyway, so
extra moisture is not a problem.  Stock bottles are checked regularly to
make sure picric acid is still wet.

I guess the question is, for labs who cannot store picric acid, do they
still use Bouins for fixation?  at least on occassion???  Or is this
fixative totally banned because of the picric acid?  I see it sold by some
companies.  I would assume careful storage is still required, and careful
wiping around lids, etc to make sure dried picric acid does not show up on
your countertops, shelves.

Gayle Callis
Veterinary Molecular Biology
Montana State University
Bozeman MT 59717-3610
406 994-4705
406 994-4303

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