The present paper deals with drying of SiO2 xerogel that leads to the decrease of the intensity of Cu(ll) spin probe EPR signal and to the signa/noise ratio as well. This effect is explained by changes of Cu(II) coordination into an EPR less sensitive one. During a sample dehydration the decrease of electric permittivity causes the increase of the dipole interaction between Cu(II) coordination polyhedral, which plays an important role in decreasing EPR signal.
