Effect of dielectric constants, sample container dimensions and frequency of magnetic field modulation on the quantitative EPR response

The dependence of the direct and relative (to reference standard situated o utside the sample) EPR response estimations on the sample's dielectric cons tant, the sample container's internal diameter and the frequency of the mag netic field modulation in quantitative EPR estimations is studied. It is sh own that it is possible to compare with good accuracy and reproducibility q uantitative results obtained with samples of different dielectric constants and inserted in sample containers of different internal and outer dimensio ns if: (a) reference standard and unknown sample are simultaneously recorde d making all calculations with the ratio I-uk/I-st; (b) the reference stand ard is situated outside the sample; (c) EPR spectrometer settings do not af fect both the unknown sample and the standard spectra; (d) low frequency (1 2.5 kHz or less) modulation of the magnetic held is used all the time. (C) 2000 Elsevier Science B.V. All rights reserved.