Standardized Test for determining Anitoxidant Values?

[Todd Warth]

Is there a standardized test, generally recognized as reliable, for 
determining the antioxidant potential of a given substance?  At least 
one post indicated that melatonin was a far more potent 
antioxidant than Vitamin E, and I recall reading (many years ago) that 
trace levels of bioavailable selenium were _dramatically_ more effective 
as an antioxidant than Vitamin E.

There are hundreds of antioxidants used in manufacturing and food 
processing.  Can anyone point me to a reference that quantifies the 
potency of these antioxidants in biological systems, and perhaps 
discusses the synergy aspect to boot?

Thanks in advance,

TW