RE: [Histonet] Zinc formalin and 10% NBF

From:"Marshall Terry Dr, Consultant Histopathologist"

Crisp to cut and crisp to look at - yes.
The phosphate in formalin buffer precipitates zinc, as, naturally, zinc phosphate, so washing between one and the other is desirable. If not, one sometimes sees haematoxyphil smudges in the tissue, and of course, cloudiness in the solution before processing. (A little acetic acid takes care of that).
Of course, the easiest course, if you want to go from zinc to formalin, is to go to unbuffered formalin.
(Why is there such a fixation for buffered fixatives - no pun intended?)

Dr Terry L Marshall, B.A.(Law), M.B.,Ch.B.,F.R.C.Path
 Consultant Pathologist
 Rotherham General Hospital
 South Yorkshire

-----Original Message-----
From: Kemlo []
Sent: 27 April 2004 07:43
To:; Wendy England
Subject: Re: [Histonet] Zinc formalin and 10% NBF

Can't you test the residual fixative for the presence or absence of zinc?
My Chemistry is not what it was but can't you do something with an element
and the double decomposition of a salt? Something to do with an element
higher up or lower down the Periodic Table that displaces an element from
a salt that is the other way round, can't remember. But NBF doesn't contain
the heavy metal does it?

Why is it important to know? All I can remember is that zinc formalin made
the tissue brittle, or was that lead? The nuclear stain was rather deep
too. Hope that helps.

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