Re: [Histonet] Neutralisation of 10% formalin using ammonia

From:Rene J Buesa

Mr. M:
  Schiff's reagent is perhaps the best, most sensitive and available reagent in any lab to test for the presence of aldehydes. If you "neutralized" formalin turns purplish with the addition of Schiff's reagent, it is not totally neutralized.
  That was my reagent of choice when I tested different formalin neutralizing products.
  Sakura provides a kit containing Schiff's reagent to test their neutralizing product.
  René J.

Mike Kirby  wrote:
Dear Histonetters.

The method of neutralising 10% formalin using concentrated ammonia solution has been well documented, and no doubt used by many Labs to dispose of their formalin waste.

My first question is, how does one verify that all the formalin has been neutralised?

One reference states that when the pH changes from 6 to 8, then sufficient ammonia has been added, and by implication, all the formalin should have been neutralised.

My second question is, would Schiffs Reagent be of any use as a double check in this methodology, because as we all know, it turns pink, even at very low concentrations of formalin, or would the final product, Hexamethylenetetramine, also react with Schiffs? Has anyone pursued this avenue?

South Africa.

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