Re: endogenous peroxidase

From:Phyllis Davie <>

Dear Ms. Hacker,
   We use the following recipe for blocking endogenous peroxidase activity
in frozen sections, smears and aspirates.  Hope it works for you.

Best of luck,

Phyllis Davie

Azide-Peroxide Block

Purpose:    To block endogenous peroxidase staining.

1.    Azide stock, 20%  (see reagent prep)
CAUTION:  Very Toxic.  May be fatal if inhaled, swallowed or absorbed
through skin.  May alter genetic material.  Contact with acid liberates very
toxic gas.
Sodium azide may react with lead or copper plumbing to form highly explosive
metal azides.   Flush with a large volume of water to prevent azide build
2.    Hydrogen Peroxide, 3% (H2O2) (purchased at any local store)
CAUTION:  Oxidizer, toxic, carcinogen (in concentrated form)
3.    Deionized water

    1.    Azide stock, 20%          1ml
    2.    Hydrogen Peroxide, 3%     20ml
    3.    deionized water           200ml
    4.    Mix thoroughly.

Storage:        refrigerated
Shelf Life:     one week
Disposal:       via sewer with voluminous flushing


on 5/31/01 8:30 AM, at wrote:

> What are you using for blocking endogenous peroxidase in acetone
> fixed frozen sections?
> I have used a weak solution of H202 which is not always effective,
> too strong and I get excessive "bubbling" of the tissue. Yes, I
> know, try a strength in between, but I was wondering if there is
> something more appropriate and less aggressive.
> I look forward to a wealth of knowledge and experience, preferably
> by 9am GMT tomorrow.
> Many thanks,
> Terry.
> Terry Hacker,
> Medical Research Council,
> Harwell,
> Didcot,
> Oxfordshire, OX11 ORD
> 01235 834393 x360

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