Quantitative Elemental Analysis for Rhodium and Palladium in Minerals by Time-of-Flight Resonance Ionization Mass Spectrometry

Results are presented for the trace analysis of Pd and Rh by time-of-flight-resonance ionization mass spectrometry (TOF-RIMS). The spectrometer, developed at the Advanced Mineral Technology Laboratory (Ontario, Canada), is based on a commercial laser-induced mass analyzer with upgrades that include independent laser ablation and ionization sources and pulsed ion optics to minimize noise caused by primary ion formation. The schemes presented for Rh and particularly for Pd detection are simpler than others reported in the literature. The experimental laser fluences were found to be in reasonable agreement with theoretical estimates. The TOF-RIMS measurements were quantified on the basis of calibration curves derived using reference samples covering 3 orders of magnitude in concentration. Minimum detection limits of ~15 parts per billion were found for both metals, with a precision of ~ ±15%. Samples from sulfide, iron oxide, and silicate minerals were also examined. The results are in excellent agreement with those obtained using dynamics secondary ion mass spectrometry.