Heterocyclic Amines: New Ion-Pair Reagents for the Simultaneous Reversible Sorption of Noble Metal Chlorocomplexes on a Hyper-Crosslinked Polystyrene Sorbent

Abstract

An effective analytical technique was developed for noble metals (NMs) determination, including Ru, Rh, Pd, Ir, Pt and Au, in solutions following geological sample digestion using reversible sorption preconcentration on hyper-crosslinked polystyrene and inductively coupled plasma – mass spectrometry (ICP-MS). For the first time, noble metals' chlorocomplexes extraction from solution was achieved by reversed-phase mechanism using heterocyclic amines, including pyridine derivatives 4-benzylpiperidine (4-BPP), 4-(2-phenylvinyl)pyridine (4-PVP), and 4-(2-phenylethylene)pyridine (4-PEP). The results showed that the use of pyridine derivatives allows the quantitative (≥ 98%) sorption of Ru, Pd, Ir, Pt and Au. The degree of sorption of these five elements did not depend on the reagent used. In the case of Rh, the crucial role of the amine basicity on the sorption efficiency was characterized. Quantitative extraction of the whole group of noble metals was achieved in the presence of 4-BPP on polystyrene Styrosorb-514 using 0.02 M 4-BPP, 1 M HCl and a solution flow rate of 1.8 mL min−1. The desorption was performed using 1 M HCl in a 1:1 (v/v) ethanol:isopropanol as the eluent. The developed scheme for noble metals reversible extraction was validated by the analysis of certified reference materials of basic and ultrabasic rocks GPt-5, GPt-6 and SARM-7 following NiS fire-assay. The determined values were in good agreement with the certified values. The estimated detection limits for the ICP-MS determination of analytes were from 0.2 to 3.0 ng g−1 for the analysis of 10 g solid rock samples.