Special thanks to all. We use 4% PFA / 0.1M PB as our standard fixative for 
certain protocols. And I'm aware that it changes form after 2 weeks. But, I 
make my 4% from this 20% stock. And I apologize for an error in my original 
inquiry the 20% is made in distilled H20 and not 0.1M PB. Thanks again. Atoska


>X-Sender: gcallis@gemini.msu.montana.edu
>X-Mailer: QUALCOMM Windows Eudora Light Version 3.0.6 (32)
>Date: Wed, 24 Mar 2004 14:54:12 -0700
>To: "Atoska S. Gentry" ,
>    Histonet@lists.utsouthwestern.edu
>From: Gayle Callis 
>Subject: Shelf life of 20% PFA/ 0.1M PB
>
>I have never made a 20% solution, rather a working/stock 4% (4 gm PFA in
>100 ml Dulbeccos PBS) In general, this is a common concentration for most
>PFA fixations and we tend to dilute the 4% for lesser concentration.
>
>Some people like their PFA fresh, then use immediately.  We store 4% PFA
>for several months, but if there is any cloudiness/turbidity in solution,
>it is tossed.  Months is a variable (not to mention people handling the
>reagent - the piggy factor!) - we have had 4% PFA go bad within a month and
>good as long as 6 months.  A lot depends on how often people dip into the
>reagent, if they are careless about sticking pipettes into stock or leave
>at RT for hours before returning to refrig.
>
>Personal rule:  store in a clean, clear glass bottle and check for turbid,
>cloudy solution before each use. Toss if that cloudy flocculant ppt shows
>up. This was discussed a couple of years ago on Histonet, you might want to
>go into archives.
>
>
>Gayle Callis
>MT,HT,HTL(ASCP)
>Research Histopathology Supervisor
>Veterinary Molecular Biology
>Montana State University - Bozeman
>PO Box 173610
>Bozeman MT 59717-3610
>406 994-6367 (lab with voice mail)
>406 994-4303 (FAX)

Atoska S. Gentry B.S., HT(ASCP)
Research Assistant III
Scott-Ritchey Research Center
College of Veterinary Medicine
Auburn University, AL  36849
Phone# (334)844-5579  Fax# (334)844-5850 


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