ИСТИНА

Noble metals (NMs: Ru, Rh, Pd, Ir, Pt и Au) are called ‘Vitamins of modern industry’ due to their unique properties and high catalytic activity. As world consumption of NMs is increasing new techniques for their determination in various types of rock formations within the concentration range of 10-9 – 10-6 wt.% are vital. Solutions obtained after the decomposition of geological materials contain NMs at a level of ng L-1 along with high concentrations of matrix components. As a result the stage of separation and preconcentration of NMs is required. Sorption preconcentration of different analytes on hyper-crosslinked polystyrene sorbents is often used in recent decades. Heterocyclic amines based on pyridine and its derivatives are most selective in relation to NMs’ chlorocomplexes in the presence of other transition metals. 4-benzylpiperidine (4-BPP), 4-(2-phenylvinyl)pyridine (4-FVP) and 4-(2-phenylethyl)pyridine (4-PhEP) were used as ion-pair reagents in this work. Sorption preconcentration of NMs was carried out in a dynamic mode on hyper-crosslinked polystyrene sorbent Stirosorb-514 (A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Russia). The most effective sorption of the whole group of NMs from model solutions was observed in the presence of a secondary amine of 4-BPP. The following optimal conditions were chosen for quantitative group sorption of NMs’ chlorocomplexes: C(4-BPP) = 0.02 − 0.06 mol L-1, C(HCl) = 0.2 − 1 mol L-1 . Hydrochloric acid solutions based on ethanol, isopropanol, mixtures of isopropanol and ethanol, as well as mixtures of ethanol and n-butanol were used for desorption of NMs in this work. Extraction of NMs compounds with heterocyclic 4-BPP is achieved due to the high solubility of the amine reagent in the organic phase. The maximum recovery was achieved by using an eluent the mixture of ethanol and isopropanol at low (< 0.5 mL min-1) flow rates of desorption. Ru, Ir and Pt were extracted quantitatively under these conditions; the recovery of other NMs was about 90%. The selected sorption system was validated by the ICP-MS analysis of certified reference materials of basic and ultrabasic rocks (GPt-5, GPt-6, SARM-7) after preliminary NiS fireassay pretreatment. Good agreement between the measured NMs concentrations and the certified values was demonstrated. This work was supported by the Russian Foundation for Basic Research (RFBR, grants 16-03-00428 and 17-03-01014 А).