Posted 16 December 2009 - 05:54 AM
I recently resolved to approach the confusing world of bacterial cells fixation for DNA staining. Among all the fixatives, three of them caught my interest (especially because we have them on stock in the cabinet).
Formalin (which is a saturated solution of Formaldehyde)
Paraformaldehyde (which is a polimer of Formaldehyde)
In the methods I have been reading, it looks like they are used quite interchangeably. Would anybody know if there is any substantial difference between these three and whether one of them is in any way superior to the other two?
Posted 16 December 2009 - 09:26 AM
Posted 17 December 2009 - 01:59 AM
One thing to note about the naming is the concentrations. This mistake happened recently on our lab. A fully saturated formalin solution contains about 40 % (v/v) formaldehyde. Most fixing requires a 4 % Formaldehyde concentration, so that is 10% of a fully saturated formalin solution (and not 4%). Bottom line: Use formaldehyde percentages.
Posted 17 December 2009 - 02:17 AM
Solution of Paraformaldehyde is formaldehyde.Formaldehyde = solution of paraformaldehyde.
So, all the 3 are the same thing. For experiments where we need purest form of Formaldehyde, we make fresh solution of formaldehyde by dissolving paraformaldehyde. Stored formaldehyde might not be pure and might have small amounts of alcohol in it.
(Correct me where I am wrong)