Quantitative EPR

From NMR Wiki

Signal intentity in CW EPR is expressed as:

where χ^'' - imaginary component of effective susceptibility
η - sample filling factor
Q - loaded resonator quality factor
P - irradiation power
Z₀ - characteristing impedance of the transmission line

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.

References

1. Yordanov, ND and Ranguelova, K. Quantitative electron paramagnetic resonance and spectrophotometric determination of the free radical 4-hydroxy-2, 2, 6, 6-tetramethylpiperidinyloxy. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 56(2):373--378, 2000. BibTeX [yordanov]