paraformaldehyde solution - for IHC (Mar/12/2008 )

Formalin and Formaldehyde are same. Just that 37% Formaldehyde is called 10% Formalin. I remember reading why these 2 names. 10% Formalin is older term because of some misconception.

Thx guys, pernesblue's post made the whole thing clear to me.

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but will it be better for reduction of autofluorescence to use freshly prepared formaldehyde?

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Paraformaldehyde vs. Formaldehyde = formalin.

Paraformaldehyde is a powder. Use 4% in PBS as above = PFA
To make 100 ml:

1. Put 80 ml DDW in a clean bottle (the PLASTIC cap will be needed later).
2. Pre warm in microwave oven to about 550C (do NOT boil!)
3. Add 4 gr paraformaldehyde (wear face mask)
4. Add 50 µl of NaOH 5M.
5. Stir capped on a stirrer.
6. Stir for a few minutes while heating gently (don’t boil!).
7. Add 50 µl of HCl 5 M.
8. Add 10 ml 10xPBS, and DDW to final 100 ml (bottle marks are good enough).
9. Place on ice to chill.
10. Can keep at 40C for a one more day, but it always recommended to make fresh.



Formaldehyde (liquid) = formalin.
Usually sold as about 40% (37%) and diluted in PBS.
As the dilution is 1:10 some people call in 4% formalin (concentration) and others 10% (vol/vol). it is the same as long as you dilute 1:10.
Good luck.

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I fix cellswith frozen aliquots (old stock) for fluorescent immunostaining , and it works fine. no autofluorescence.
However : Never freeze it again when thawn.

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i'll say it again

formalin is 40% formaldehyde

it is simply a name given to a dilution for ease of use

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10% Formalin = 3.7-4% Formaldehyde

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well yeah

but people seemed to be running round in circles over a simple matter

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