Multi-element determination of Pt, Pd and Ir traces in environmental samples by ICP-MS after pre-concentration

An automated flow analysis method with on-line column pre-concentration/ inductively coupled plasma mass spectrometry (ICP-MS) was developed for the simultaneous determination of Pt, Pd and Ir in environmental samples. The system is based on retention of the analytes onto a column filled with 1,5-bis (2-pyridyl)-3-sulphophenyl methylene thiocarbonohydrazide immobilized on an aminopropyl-controlled pore glass (PSTH-cpg) placed in the injection valve of a simple flow manifold. The retained platinum group metals (PGMs) were subsequently eluted with a mixture of HNO3 and thiourea. The effects of chemicals and flow variables were investigated. The optimized operating conditions were: sample pH 3.2, sample flow rate: 1.1 mL min−1; eluent flow rate: 2.1 mL min−1 and eluent 0.03% m/v thiourea solution in 3.2% (v/v) HNO3. The detection limits obtained were 78.5 ng L−1 for Pt, 55.5 ng L−1 for Pd and 0.1 ng L−1 for Ir. The enrichment factors were 18, 2.3 and 43 for Pt, Pd and Ir, respectively. The accuracy of the method was checked by the analysis of certified reference materials and by determining the analytes content in spiked environmental samples. Recovery was found to be in the range 93–107% in all cases.