3.4. Data treatment
The measurement results are treated presented in accordance with the REQUIREMENTS of ISO/IEC 17025:2005 [39]. The limits of detection (LOD) were calculated from the 3σ-criterion according to the IUPAC 1998 recommendations for the presentation of the results of chemical analysis [40]. All the procedures were characterized by the repeatability relative standard deviation (RSD), and the minimum values of this error curve was used as another metrological parameter. To determine the significance of contributions to the signal of the control experiments, the series were compared by Student's t-tests; variances were compared using the Fisher test.