A shelf-life doesn't mean much for a bottle of hydrogen peroxide once it has been opened.
 
Decomposition (to water and oxygen) is catalyzed by traces of many substances, including metals and phosphate ions. In my lab, a long time ago, we used a 1ml syringe with a long needle to withdraw small volumes of 30% H2O2 for dilution. From time to time the stock bottle would die overnight; I suspect that this was due to contamination by traces of iron from the needle. 

Years ago we changed from 30% H2O2 to a solid compound called urea hydrogen peroxide (UHP). This is treated as 35% w/w H2O2. It seems to be very stable, and not disturbed by digging it out of the bottle with a nickel spatula. A 1% solution of H2O2 made from UHP (2.86 g in 100 ml water) can be kept on the bench for a few days and replaced before it has time to decompose.  

----- Original Message -----
From: arvind 
Date: Friday, September 28, 2007 4:31
Subject: [Histonet] hydrogen peroxide quenching- shelf life
To: Histonet@lists.utsouthwestern.edu

> is there any shelf life for  H2O2 so that it can be 
> conformed before
> quenching unless its too late how can we know the purity of it
> 
>  *Arvind Singh Pundir*
> National Brain Research Centre
> Manesar, Gurgaon- Haryana- INDIA
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> Histonet@lists.utsouthwestern.edu
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