Vy. Nagy, CHOOSING REFERENCE SAMPLES FOR EPR CONCENTRATION MEASUREMENTS .1. GENERAL INTRODUCTION AND SYSTEMS OF S=1 2/, Analytica chimica acta, 339(1-2), 1997, pp. 1-11
Paramagnetic centers in the reference samples used in electron paramag
netic resonance (EPR) spectrometric concentration measurements often d
iffer in nature from the centers to be determined in unknowns. Quantit
ations based on such an approach can be correct only if the difference
s in specific intensities of the two signals, that is, the inequality
of the signal areas per paramagnetic particle, is taken into account.
This series of papers provides tabulated values that characterize the
specific intensities of X-band EPR signals for paramagnetic species of
various types in solid samples. The data were obtained by quantum-mec
hanical calculations comprising exact diagonalization of the spin Hami
ltonian matrices. One can generally use the tabulated values to calcul
ate the correction factor when a dissimilar reference sample has to be
employed. Examination of this data can also help in selecting a refer
ence sample whose paramagnetic centers provide an EPR signal very clos
e in specific intensity to the signal of the analyte, no matter how mu
ch these two paramagnetic centers differ in nature. With such a refere
nce sample, no correction is necessary at all, This first part of the
series provides a general introduction and the data for the simplest c
lass of paramagnetic species with the effective spin of 1/2.