Hi. I have stored 4% paraformaldehyde frozen in 50ml flacon tubes and at 4C in a glass bottle without any problems (used for immunofluoresence). Now I have been told that I should not keep 4% PFA in a glass bottle....does anyone know why? Or whether that is true?
Hi Julia,
PFA slowy decomposes at neutral to slightly basic pH, releasing formaldehyde (which then fixes your sample, it reacts with a lot functional groups; pure PFA itself is not a fixative).
You can store the solution at 4°C, but be aware that free formaldehyde oxidizes to formic acid with oxygen, just a matter of time and your solution does not work any more for fixation. E.g. glutaraldehyde is available as aqueous solution in sealed glass bottles (under Argon). As soon as opened, the air oxidation starts (if not flushed with Argon) and after a certain time, it is inactive for fixing, all groups are oxidized to the acid form. I usually discard the solutions after 2-3 weeks.
If you want to be sure to have maximum reactivity, only use freshly thawed solutions and discard the rest. Using glass or plastic bottles does not make any difference at all.
Hi Julia,
PFA slowy decomposes at neutral to slightly basic pH, releasing formaldehyde (which then fixes your sample, it reacts with a lot functional groups; pure PFA itself is not a fixative).
You can store the solution at 4°C, but be aware that free formaldehyde oxidizes to formic acid with oxygen, just a matter of time and your solution does not work any more for fixation. E.g. glutaraldehyde is available as aqueous solution in sealed glass bottles (under Argon). As soon as opened, the air oxidation starts (if not flushed with Argon) and after a certain time, it is inactive for fixing, all groups are oxidized to the acid form. I usually discard the solutions after 2-3 weeks.
If you want to be sure to have maximum reactivity, only use freshly thawed solutions and discard the rest. Using glass or plastic bottles does not make any difference at all.
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