Ecological Systems and Devices Annotation << Back Optimization of Sample Mass and Dilution for Elemental Determination in Soils by ICP-OES Method Zemtsova E.S., Kolobov A.P., Alimova G.S., Tokareva A.Yu., Pitukhina A.Yu., Yakimov A.S. Using a typical grey forest soil as an example, the influence of sample mass (0.25, 0.5, 1.0, and 4.0 g) and fi nal dilution factor on the results of macro- and microelement determination by inductively coupled plasma optical emission spectrometry (ICP-OES) after acid digestion of samples with aqua regia in a microwave system was studied. It was experimentally established that the use of the maximum sample mass (4.0 g) provides the best representativeness of the analysis by averaging the natural micro-heterogeneity of the soil. It was shown that a fixed volume of acid reagents (8 ml) is sufficient for effective digestion, and the phenomenon of backsorption on the insoluble residue does not have a significant impact on the results. The investigation of dilution regimes (10-fold and 50-fold) revealed the necessity of a differentiated approach: for macroelements (Fe, Al) with a 4.0 g sample mass, a 50-fold dilution is required to comply with the linear calibration range, while for microelements, a 10-fold dilution is sufficient to preserve sensitivity. Based on the obtained data, an optimized analysis scheme for soils of similar type is proposed, which includes digestion of a 4.0 g sample followed by differentiated dilution – 50-fold for macroelements and 10-fold for microelements. The developed protocol allows for achieving an optimal balance between sample representativeness, accuracy in measuring high concentrations, and sensitivity in determining trace amounts of elements. Keywords: soil sample preparation, ICP-OES, microwave digestion, aqua regia, elemental analysis, sample mass, final dilution, macroelements, microelements. DOI: 10.25791/esip.5.2026.1592 Pp. 14-22.