ozone

Dear engineers and scientists,

Measuring and artificially producing hydroxyl radicals is relatively new research with great challenges due to short half life. I have asked this question on many forums to gather as much information as I can and my question is:

How can we measure hydroxyl radical concentration? I am only interested in airborne concentration, hydroxyls in water and cells are not relevant to my research.

Also there are few articles mentioned every time in these type of discussions and they are: