Simultaneous determination of traces of Pt, Pd, Os, Ir, Rh, Ag and Au metals by magnetic SPE ICP OES and in situ chemical vapour generation

Abstract

Herein, a chelating sorbent that employs magnetic nanoparticles (MNPs) functionalized with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide (DPTH-MNPs) has been used to develop a simple method for the analysis of trace amounts of metal ions present in environmental samples; the method combines on-line magnetic solid phase extraction (MSPE) with atomic spectrometry. Thus, a flow injection FI-MSPE/cold vapour generation system coupled to an inductively coupled plasma optical emission spectrometry (ICP OES) method for the determination of trace amounts of noble metals, platinum group elements (PGEs: Ir, Pd, Pt, Os, and Rh), and Au and Ag in environmental samples has been developed. A magnet-based reactor designed to contain DPTH-MNPs was placed in the injection valve of the FI manifold. Several chemical and flow variables were considered as factors in the optimization process using two central composite designs; with the optimized method, the experimental detection limits for simultaneous determination, calculated as the concentration of analyte giving signals equivalent to three times the standard deviation of the blank plus the net blank intensity (LOD, peak height), were 1.5 μg L⁻¹, 0.03 μg L⁻¹, 0.65 μg L⁻¹, 0.62 μg L⁻¹, 0.57 μg L⁻¹, 0.03 μg L⁻¹, and 100 μg L⁻¹ for Pd, Ag, Os, Au, Ir, Pt, and Rh, respectively. The method offers relatively good precision (RSD 1.8–7.2%). The accuracy of the proposed method was verified using certified reference materials (CMRs, NIST 2557 autocatalyst, TMDA 54.4 fortified lake water, and SRM 1643e trace elements in fresh water) and by determining the analyte contents in spiked aqueous samples. Sea water and tap water samples obtained from Malaga (Spain) were also analysed. The determined values were in good agreement with the certified values, and the recoveries for the spiked samples were in the range of 91.8–108.1%. Additionally, the proposed method was applied in the simultaneous determination of the abovementioned 7 elements with a sample throughput of about 17 h⁻¹, thereby reducing the time of analysis and the volumes of reagents and sample required.