Quantitative EPR

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Signal intentity in CW EPR is expressed as:

$I = \chi^{''} \eta Q \sqrt{P Z_0}$

Standard materials

TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy) dissolved in water was proposed[1] as a primary standard for determination of concentration of free radical species by EPR. Concentraion of TEMPOL standard solutions can be determined by measurement of absorbance at 436.68 nm and using molar absorptivity of 13.2±0.1 LM^-1cm^-1. Concentration of free radical species was found at ~98% of expected based on the weight of dissolved material.