[Histonet] Shelf life of 20% PFA/ 0.1M PB

From:Gayle Callis

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
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)

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