To fellow flowers, As a veterinary pathologist who works with both formalin and paraformaldehyde solutions, I felt that Dr. Zbigniew Darzynkiewicz' answer gave some of the most practical information. The formaldehyde (dissolved gas) in formalin solution or made from 37% 'formaldehyde solution' can be extensively polymerized while the formaldehyde (dissolved gas) made from a fresh paraformaldehyde solution is largely monomeric. In addition, in formalin or formaldehyde solutions, breakdown and rearrangment products from the formaldehyde gas form gluteraldehyde and other adehydes spontaneously. As noted, most formalin solutions also contain methanol. >From a practical aspect, it means that formalin and 'formaldehyde' solutions will destroy some antigens that a fresh paraformaldehyde solution might preserve. The formaldehyde in paraformaldehyde solutions will also undergo spontaneous polymerization and breakdown with time and therefore, from a practical aspect, may not preserve the test antigen with time. For some of the antigens that we work with, paraformaldehyde solution is useful for days to about a week after it is made and after that, the antigen is not preserved to the same extent as a fresh solution. Other antigens are not labile and can be fixed even in formalin or aged paraformadehyde (or alchohols for that matter). Anyone using paraformaldehyde solutions should be aware of these issues and work out the optimal conditions for their particular antigens. Carol W. Johnson, DVM PhD Pharmacia Corp. Kalamazoo MI
This archive was generated by hypermail 2b29 : Sat Mar 10 2001 - 19:31:29 EST