Using 4% PFA in the lab - (May/27/2012 )
When doing immunostaining, does the fixing step involving PFA have to be done under a lamina flow cabinet? There has been contradictory practices around with regards to the usage of 4% PFA in the lab.
Does that mean that I would also have to conduct all my washing & incubation steps in the hood?
In my opinion 4 % PFA should always be handled under a fume hood! We usually do the incubation and at least the three immediately following washing steps under the fume hood.
While it is good practise to limit exposure, the amount of PFA (well, actually formaldehyde when it is in the gaseous form) released from solution is tiny. The OSHA regulations state 0.75 ppm for 8 hours as the maximum for workers (or 2 ppm over a 15 min time period). You have to get pretty close to a fixing solution to start noticing the effects, which according to the EOHSS start being noticeable at 0.1 ppm...
Fixing, yes, hood is good, washes, hood is fine, but you don't have to.
I don't do this in a hood but I'm usually only doing a few plates at a time and my the PFA is only open to the air for a few seconds. After I wash with PBS I quickly unscrew the lid of my PFA tube, add some to my plates of cells, put the lids back on the plates and recap the tube of PFA. When they're done fixing I remove the lid from the plates and immediately asperate the PFA then continue PBS washing.
I work with 96-well formats when I'm doing my staining so there are ALOT of wells to get through (wash, stain).
I make my PFA in the fume cupboard, but then just use it on the bench. And I use 96 well plates too