Peroxide or peroxidase?

I hope its hydrogen peroxide, check the following

Article An Improved Chemiluminescence Method for Hydrogen Peroxide D...

Article Optimized Assay for Hydrogen Peroxide Determination in Plant...

Apart from the above two method mentioned by Dr. Raghuram you can use Amplex red ROS quantification kit from invetrogen, which is highly sensitive and is reproducible. The KI –based H2O2 quantification also is good method but not very sensitive and you need good amount of sample to start with. You can easily find the details of Amplex Red kit if you google it.

Correction Vivek.  I'm not Dr. :)

And the quantification kit is expensive I guess

Thank you very much, dear Raghuram and Vivek Ambastha.

Welcome sir....

Sir,

      You can also try out the chemiluminescence method with luminol.

Thank you, Sarang.