Determination of Pt, Pd, Ru, Rh in Geochemical Samples by ICP-MS with Microwave Digestion and Dual-cloud Point Extraction

Traditional cloud point extraction methods commonly enrich elements in the viscous surfactant. However, the viscosity of the solution will adversely affect the detection signal of the plasma. Harmful agents such as methanol are usually adopted as a thinner to reduce the viscosity of the organic phase, but the organic component affects the stability of the plasma, and organic absorption on the injection tube will enhance elemental memory effect. These disadvantages limit the widespread application of Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in cloud point extraction. A method to determine Pt, Pd, Ru, Rh in geochemical samples by ICP-MS based dual-cloud point extraction has been established, and is reported in this paper. After the microwave digestion procedure, first cloud point extraction is performed on the sample solution using DDTP as the sequestrant and Triton X-114 as the surfactant. HNO₃ is added into the organic phase, and second cloud point extraction is performed by heating so that Pt, Pd, Ru, Rh enter the water phase from the organic phase. Enrichment factors are 45, 33, 18, 35, and detection limits are 0.05, 0.02, 0.10 and 0.03 μg/L for Pt, Pd, Ru and Rh, respectively. The proposed method succeeds in the simultaneous enrichment of trace platinum group elements in complex matrix geochemical samples, improving the stability of the ICP-MS measurement.