To the Precision of Measuring Concentrations of Nitroxide Radicals in Polymers by EPR Technique

Abstract

The precision of measuring concentrations of nirtoxide radicals in polymeric matrixes using modern electron paramagnetic resonance spectrometer is analyzed. The contributions of the radical nature and concentration, signal-to-noise ratio, and the integration procedure are tested as factors influencing on the precision of the measurement. It has shown that recording spectra with modern EPR spectrometer with possibility of computer analysis of spectra, the contribution of the integration error to the total error strongly depends on the signal-to-noise ratio. If the ratio is < 20, its contribution increases fast with the decrease of this parameter. If this ratio is ≥ 20, the input of the integration error becomes negligible, and the main contribution to the total error of concentration measurements comes from errors of the Q-factor determination, which are usually close to 8–10%.