From: /G=Gerhard/S=Nebe-von-Caron/OU=1890CHPE/O=TMGB.URC/@LANGATE.gb.sprint.com
Date: Fri May 03 1996 - 04:19:00 EST
As said in another message, this comes up again and again. Paraformaldehyde are 'chains' of formaldehyde which is normally created by boiling paraformaldehyde, thus heating also dissolves it in water. With time it can turn into formic acid, thus to stabilize formaldehyde solutions approx. 15% methanol is added which is what one commonly buys as formalin solution. Gerhard Nebe-v.Caron Unilever Research, Colworth Lab. Sharnbrook, Beds. GB-MK44 1LQ Tel.:+44(0)1234 222066 Fax.: 222344 Gerhard.Nebe-von-Caron@unilever.com ______________________________ Reply Separator _________________________________ Subject: Re: Paraformaldehyde fixative Author: rmoldwin@midway.uchicago.edu at INTERNET Date: 02/05/96 23:29 At 09:17 AM 4/29/96 EST, you wrote: >First, make it fresh. I make a fresh batch each week and store @ 4C. >For 2% I dissolve 2g paraformaldehyde in 75 mL PBS, add a few drops of 5M KOH >until dissolved, adjust pH to 7.0 with HCl. >Daniel >CDC I've read this in several places, that one must make fresh PF solutions. I have used 2% PF in PBS over a year old (stored dark at 4C) and have not noticed any problems. I have also analyzed samples a month or two after fixing without problems, and no apparent signal (FITC) degradation. Is there any hard data that shows that PF solutions go bad? If so, what happens to it? Is there any reference for this? --Rich ^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^ Richard Moldwin, M.D., Ph.D. Section of Pediatric Hematology/Oncology University of Chicago Hospitals Wyler Room C408, MC 4060 5841 S. Maryland Ave. Chicago, IL 60637 E-mail: rmoldwin@midway.uchicago.edu WWW: http://rmoldwin.bsd.uchicago.edu Phone 312-702-6808 Fax 312-702-9881
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