It has been found that silica chemically modified with dipropyl disulfide groups (DPDSS) quantitatively extracts palladium(II) from solutions in the acidity range from 4 M HCl to pH 4 and gold(III) in the range from 1 M HCl to pH 2 with a partition coefficient at the level of n × 10⁴ cm³/g. The adsorption of palladium(II) and gold(III) at room temperature is highly selective, whereas non-ferrous and other platinum metals are not adsorbed. Sorption-atomic absorption, sorption-ICP-atomic emission, and sorption-photometric methods for the determination of palladium and gold have been developed using DPDSS. The accuracy of the methods was tested by the analysis of certified reference samples.

Pine sawdust and malt sprouts modified with orthophosphoric acid and carbamide have been proposed for solid-phase extraction (SPE) of nonferrous, heavy, and precious metals and their subsequent determination in the environmental samples by inductively coupled plasma optical emission spectrometry (ICP-OES). Modified adsorbents were characterized by SEM, TGA, and FT-IR and compared with native matrixes. SPE of some nonferrous and precious metal ions by biosorbents was studied. Depending on the SPE conditions, it was possible to separate nonferrous and heavy metals from alkali and alkaline earth metals. The proposed adsorbents are effective for preconcentration of nonferrous and heavy metals from natural waters and precious metals from solutions after digestion of geological samples.

Silicas chemically modified with a number of sulfur-containing groups (mercaptopropyl, mercaptophenyl, dipropyl disulfide, thiadiazole thiol, dithiocarbamate and thiourea derivatives) were proposed for the separation and preconcentration of precious metals. These adsorbents quantitatively extracted precious metals from 0.5 to 4 M solutions of hydrochloric acid. It allowed their separation from high concentrations of non-ferrous, alkaline earth, alkali and some other related metals. The selectivity of separation of kinetically labile precious metal ions in ligand substitution reactions from kinetically inert ones depended on the nature of sulfur atom within the functional group of adsorbents and increased when passing from thione to thiol sulfur. Approaches for the preconcentration of precious metals using silicas chemically modified with sulfur-containing groups prior to their AAS, ICP-OES, and ICP-MS determination in ores, concentrates and their processing products were proposed. The correctness of the developed methods was confirmed by the analysis of certified reference materials.