No abstract

Hlghperformance llqukl chromatography Is applied to the determlnatlon of gold( I ) cyanide uslng on-line sample preconcentration. The complex Is resolved by ion-interactlon chromatography on a C18 column uslng a mobile phase of 3268 acetonitrile-water contalning 5 mM tetrabutylammonh Ion, with detectlon by UV absorptlon at 214 nm. Samples are preconcentrated by passage through a C18 precolumn previously condltloned with the above m M e phase. The cholce of Ion-lnferactlon reagent is discussed In terms of the Ionic retentlve capacity of the precolumn and the llnear range of the calibration plot. Under optimal condltlons quantitative blnding of aurocyanide was observed for sample volumes of up to 3 mL, giving a detectlon llmH of 0.43 ppb gold. The preclslon of the method at the 10 ppb gold level was 0.9% relatlve standard devlatlon. The chromatographic condltlons employed are shown to be suitable for the simultaneous determination of ultratrace levels of the cyano complexes of Au( I), Pd( I I), and pt( I I ) In solutlons contalnlng high concentrations of free cyanide ion.In an economic climate where the price of precious metals is high, it becomes feasible to process even very low grade ores.This in turn produces a demand for accurate analytical procedures for these elements which are applicable to trace and ultratrace concentrations. In gold-processing plants and in geological exploration, it is often necessary to analyze solutions containing precious metals in the 1-10 ppb range.For many years, spectroscopic and electrochemical methods have proved successful for the analysis of precious metals, especially gold ( I ) . Apart from the traditional fire-assay method, atomic absorption spectroscopy (AAS) has been the most widely used method. Flame AAS is suited to the determination of gold at levels of approximately l ppm and higher, whereas graphite furnace AAS is applicable to much lower concentrations. When analyses in the low parts per billion range are required, it is generally necessary to preconcentrate the sample by solvent extraction, typically using a liquid ion-exchanger in MIBK as the extracting solvent (2, 3 ) . Other analytical techniques for gold such as inductively coupled plasma atomic emission spectrometry ( 4 ) , electroanalysis ( 5 ) , X-ray fluorescence (6), and neutron activation analysis (7) either have insufficient sensitivity for ultratrace applications or are very time-consuming.In a recent report (8), we have described a chromatographic method for the determination of Cu(I), Ag(I), Fe(II), Co(II), Fe(III), Au(I), Pd(II), and Pt(I1) as their cyano complexes. In this method, the metal complexes were separated by ioninteraction chromatography (IIC) using either a C18 or CN stationary phase and an eluent containing acetonitrile-water and an appropriate ion-interaction reagent (IIR). Detection was achieved by UV absorption at 214 nm, giving a detection limit of 0.26 ppm for gold. While separation of the above eight metal complexes required a relatively long time (up to 35 min), the main advantage...