Is it ok to use expired formaldehye for fixation of voucher specimen and tissue samples for histological analysis?

16 October 2017 1 2K Report

I am taking gonad samples of fishes for histology to look at maturation stages. I couldn't find definite information if expired formalin can be used to make 10% buffered formalin or if it would still work as a fixative. Thanks for your input.

Luca Stirnimann

Hello,

I have similar question. I have expired formalin - neutral buffered 10% and I need to fix zooplankton samples (exp. Jan 2019).

I would like to know if I can still use it or I should definitely make/buy a new one.

I know that after a while, buffered formalin produces Methanol that promotes clumping of proteins instead of the cross-linking of proteins that formaldehyde performs. But, does it really compromise the fixation of relative "big" organisms like zooplankton?

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