Trace enrichment and determination of platinum using a FIA-ICP system

Abstract

The platinum group of metals (PGM), in particular platinum, palladium and rhodium, have lately become indispensable to modern industry. Due to South Africa's extensive PGM reserves, South Africa are currently the World's largest PGM-supplier. Since ICP-OES are frequently used for the determination of these elements, a procedure was developed for the determination of platinum, palladium, rhodium and nickel, the base metal normally associated with PGM deposits. The concentrations at which these elements occur in deposits and environmental samples are however generally too low for direct determination with ICPOES. In order to improve the detection limits of the ICP-OES, the instrument was coupled to a FIA system which contained a micro-ion exchange column for the on-line preconcentration of platinum. The performance of three different ion exchangers, namely alumina, POL YORGS IV and Dowex 1, were compared. The advantages of the preconcentration FIA-ICP systems were maximized by optimization of several of its operating parameters. These parameters included the acidity of the sample, the concentrations of the carrier and eluent streams, flow rates, preconcentration and elution times as well as, the temperature at which a system was operated. The best preconcentration was eventually obtained with the alumina micro-column. When compared to conventional ICP-OES, this system yielded an order two magnitude improvement in the platinum detection limit. This corresponded to an enrichment factor of 25. 5. The precision of the technique was better than 5 % RSD at the O. 72 mg/£ level. Analysis of a spiked water sample further gave a 106 % recovery at the mg/£ level. A sample rate of 5. 7 samples/h was obtained with the system, which corresponded to a concentration efficiency of 2.45. Finally, the consumptive index of the system was only 0.24, which indicated efficient utilization of the sample available.