The  total  body  radical  burden  can  be  estimated  by which of the following methods?
The total body radical burden can be estimated by measuring the products of lipid peroxidation:

FOX (Ferrous Oxidation in Xylenol) Assay 
	Lipid peroxides can be measured by the ferrous oxidation in xylenol orange (FOX) assay. Under acidic conditions, they oxidize Fe 2+ to Fe 3+, which forms a chromophore with xylenol orange.
Estimation of Dialdehydes
	‒ The dialdehydes formed from lipid peroxides can be measured by reaction with thiobarbituric acid, when they form a red fluorescent adduct. The results of this assay are generally reported as total thiobarbituric acid reactive substances,TBARS.
Measurement of Pentane and Methane in Exhaled air
	‒ Peroxidation of ω-6 polyunsaturated fatty acids leads to the formation of pentane, and of-ω3 polyunsaturated fatty acids to ethane, both of which can be measured in exhaled air.

Reference- Review of biochemistry by Rebecca James Perumcheril Pg-412
FOX  Assay
Estimation of Dialdehydes
Measurement of Pentane and Methane in exhaled air
All of the above