How to measure reactive oxygen species using a specific fluorescent dye/indicato - (Mar/21/2013 )

When a fluorescent dye/indicator is added to a cell culture to show the ROS in the culture, how can the amount of reactive oxygen species be estimated or determined? Is there an easy method, possibly not costly?

Thanks for the responses!

you can determine relative fluorescence of the culture medium and compare to a standard curve.

I am not sure if its of any help but the following article might be useful it's called:
Measurement of Reactive Oxygen Species in the Culture Media Using Acridan Lumigen PS-3 Assay
and the link is:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3165859/