Have you performed experiments that show more of a benefit for storing samples in formalin over 70% alcohol in your lab? I have one researcher who, based on their experience in cultured cells, knows that anything over 10 minutes of fixation time causes their antibody staining to diminish using one particular antibody. I'm well aware of the current trend towards longer fixation times and generally believe that more is better. Because of evidence to the contrary, I cannot bring myself to recommend as a matter of routine, to store samples in formalin, especially for research purposes.
I much prefer to have the samples paraffin processed or cryo embedded after a defined period of time in fixative, and store the tissues in those two forms rather than anything aqueous or alcoholic.
Jackie - I'm not aware of any vendors who sell 4% formalin made from PFA in large quantities, simply due to the problem of re-polymerization upon storage. We get 16% solution in ampules, and then dilute in PBS to 4%. Perhaps that might work for you?
Teri Johnson, HT(ASCP)QIHC
Managing Director Histology Facility
Stowers Institute for Medical Research
1000 E. 50th St.
Kansas City, MO 64110
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