Alternative method for detection of free radical species

[Zellinger]

Is anyone familiar with methods for detecting free radicals except EPR (ESR) spectroscopy? I'm particullary interested in detection of free radical via polymerization reactions i.e polymerization of acrylonitrile and acrylamide. What are the exact experimental conditions for this kind of detection to work?

 

Well here is my problem - we have been investigating this redox reaction and we suspect that it's mechanism involves free radicals. We have done the EPR spectroscopy but results came out negative, so my mentor said we can try to do polymerization test to be sure there aren't any radicals present at all (since this result is a bit odd). Our reaction only occurs under alkaline conditions (pH = 12 or above) at significant rate. So we added acrylonitrile to our reaction mixture under inert nitrogen atmosphere (to exclude oxygen) but no turbidity appeared as it was stated in several journals. Then with tried with species we knew is in free radical form (in our case we used ascorbate, some papers state it's initiator for this reaction) but test again came out negative. So there was a problem somewhere and I couldn't figure it out. Today I have found that acrylonitrile if technical-grade contains polymerization inhibitor ethylhydroxyquinone and should be purified (it think by destillation) prior to use. But in the same article I have found out that AN polymerizes spontaneously under strong alkaline conditions which is our case so even if purified we couldn't use this reagent for detection.

 

Does anyone know if similar reaction could be performed with acrylamide and what are exact experimental conditions? I have searched OVID journals and it's mentioned in couple of papers but I haven't found any detailed explanation of the procedure. Thank you in advance!