A criterion is proposed to analyze the dependence of conductivity data vs. frequency log sigma vs. log omega in ionic conductors. The derivative of experimental log sigma vs. log omega data enables a better differentiation of different contributions to the conductivity (bulk, grain boundary, near constant loss (NCL) and others). The usefulness of this procedure is tested for cases with different degrees of convolution between different relaxations. The criterion is applied to real data of two solid electrolytes with perovskite structure. The analysis of La0.5Li0.16Sr0.16TiO3 (LLSr) compound allowed the differentiation of bulk and NCL contributions. The analysis of the fast ion conductor La0.6Li0.2TiO3 (LLTO-06) required an enlargement of the frequency window to precisely study the bulk conductivity and correlation effects on Li motion (determination of n parameter). This methodology can be extrapolated to other solid electrolytes. (C) 2012 Elsevier B.V. All rights reserved.