R.R. Barefoot

Recent advances in the determination of the platinum group elements and gold

Accurate determinations of the platinum group elements (PGEs) and gold, known as the precious metals, have always been difficult tasks. The metals are often present at trace levels in sample types of complex composition. This situation has improved recently due to developments of instrumental methods and their applications to analyses of the precious metals in a variety of matrices. Attention has been given to determinations of traces of precious metals in biological, clinical and environmental samples. Foremost in importance is inductively coupled plasma mass spectrometry (ICP-MS) which has provided a sensitive means of simultaneous determination of traces of PGEs and gold. Important extensions and improvements in atomic absorption spectrometry (AAS), nuclear and electrochemical methods have been reported also. More research on sample treatments, especially fire assays, applied to PGEs has been carried out. Chlorination has proven to be a viable alternative to fire assays for preconcentration of PGEs and gold in analyses of geological materials. In addition, the recent availability of some additional reference materials will be of great assistance in research work on precious metals.

Distribution and speciation of platinum group elements in environmental matrices

Abstract The use of platinum group elements (PGEs) as components of autocatalytic converters attached to motor vehicles has resulted in serious contamination of the environment by Pt, Rh and Pd in nanocrystalline forms. Trace concentrations of PGEs, particularly the major component Pt, in environmental samples have been measured by sensitive instrumental procedures. These data have raised further questions about the nature of Pt species in contaminated soils and in plants grown in them. The focus of attention is changing from accumulations of data expressing total concentrations to investigations of speciation. Application of analytical procedures for research on speciation has provided information concerning transformations of Pt compounds in contaminated soils, the uptake of Pt by plants and the nature of Pt compounds in vegetation. Determination of background levels of precious metals in clinical and environmental matrices has required the development of analytical methods which combine uses of minimal quantities of reagents, and as small a number of chemical operations as possible to yield very low procedural blanks. Sensitive instrumental methods based upon high resolution inductively coupled plasma mass spectrometry and adsorptive stripping voltammetry have proven to be valuable for this work.

Determination of platinum and gold in anticancer and antiarthritic drugs and metabolites

Abstract This is a review of methods for the determination of two of the precious metals, platinum and gold, in pharmaceutical products and in biological materials containing these elements. The information presented here is drawn from a large number of reports published in the period 1990–1995. In addition to methods for determination of the total metal contents of biological samples, important work on the separation of intact drugs and of biotransformation products by means of high performance liquid chromatography is summarized. Instrumental techniques for determinations of the metals include the following: atomic absorption spectrometry; UV/Vis spectrometry, and derivatization reactions followed by spectrophotometric measurements; inductively coupled plasma-atomic emission spectrometry and-mass spectrometry; nuclear activation; and, sensitive electrometric methods. Recent reports related to stability and storage of samples are also included.

Preconcentration of trace elements in potable liquids by means of a liquid membrane emulsion for flame atomic absorption determination

SummaryA liquid membrane emulsion was developed for the simultaneous extraction and preconcentration of traces of Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn in potable liquids. After preconcentration, the eight elements were determined by flame atomic absorption spectrometry (FAAS). The results of analyses of potable water, beer and soft drinks, each from five or six different sources are listed. Data from the preconcentration method were compared with corresponding data obtained from the direct determination of the elements by graphite furnace atomic absorption spectrometry (GFAAS). Differences in results for trace elements between the liquid membrane emulsion-FAAS method and the GFAAS method were in the ranges of ±10% (water), ±9% (beer) and ±14% (soft drinks) for most of the trace elements. The satisfactory agreement meant that analyses of such liquids for trace elements can be carried out accurately with less expensive and widely available FAAS equipment.

Inductively coupled plasma mass spectrometry for the determination of platinum group elements and gold

Abstract The determination of the platinum group elements and gold by means of inductively coupled plasma mass spectrometry is reviewed. The technique has been applied to analyses of geological, biological, and botanical samples, water and airborne particulate matter. The multi-element capability of the technique and the excellent detection limits have been distinct advantages in research programs which require accurate determinations of small concentrations of precious metals.

Extraction and enrichment of cadmium and manganese from aqueous solution using a liquid membrane.

A liquid membrane containing 4% di-2-ethylhexyl phosphoric acid and 5% sorbitan monooleate in kerosene is used in the form of an emulsion for the simultaneous extraction and concentration of cadmium and manganese from aqueous solutions. When 4% tri-n-octylamine is included in the membrane composition, only manganese is extracted while cadmium remains in the sample solution. The extracted elements in the concentrate are recovered by breaking the emulsion with n-butanol. Recoveries of cadmium and manganese range from 92-104% for 60-ml samples containing 2-9 mug of each element.

Detection of noble metal depletion in layered mafic intrusions: a potential aid to exploration for platinum-group element deposits

Abstract In layered mafic intrusions, economically important platinum-group element (PGE) mineralisation can result from collection of PGE and Au from the silicate melt by Ni ( ± Cu) S droplets, which settle to form PGE- and Au-enriched layers. An important consequence is that the PGE and Au are depleted in the remaining silicate fraction. The ability to recognise PGE and Au depletion in rocks crystallised from a depleted melt would be useful in exploration for discriminating between favourable (containing PGE- and Au-depleted silicates) and unfavourable layers (those that had not experienced NiS collection of PGE and Au). Drychlorination was applied to drill core samples of the Fox River Sill (Manitoba, Canada) in order to remove metallic minerals. The remaining silicate fractions were digested by microwave heating in a mixture of HFHClHNO 3 , evaporated to near dryness, re-digested in aqua regia, and re-constituted in distilled de-ionized water. The solutions were analysed by ICP-MS for PGE and Au. The PGE and Au contents of the silicate fractions of samples collected from mineralised layers were significantly depleted relative to the PGE and Au contents of silicate fractions of samples collected from a non-mineralised layer. Verification of the ICP-MS method for the determination of Pd was carried out by means of DCP-AES. Instrumental neutron activation analysis (INAA) was used to verify the method for Au and Ir.

Separation and enrichment of iron (as Fe3+) and eleven metal ions in natural waters using a liquid membrane

Abstract A liquid ion-exchange membrane was developed for the separation and quantitative recovery of iron, as Fe 3+ , and other cations from natural waters under controlled pH conditions. The influence of the pH of the aqueous sample on the extraction of eleven cations is illustrated. Quantitative extractions of Fe 3+ , Co 2+ and Ca 2+ at concentrations of 0.1–1.0 μg l −1 from aqueous solutions are demonstrated. The average recovery of Fe 3+ under optimized conditions is 99.5% with a relative standard deviation of 1.7% ( n = 8). Ion concentrations are measured by atomic absorption spectrometry.

The Separation and Enrichment of Trace Levels of Palladium in Water by a Liquid Membrane Containing Tri-N-Octylamine

Abstract The separation and enrichment of palladium (as PdCl4 2-) from aqueous solution was carried out by means of a liquid membrane in the form of an emulsion. The liquid membrane consisted of a ...

Solid Introduction to an ICP-Atomic Emission Spectrometer for the Analyses of Metals Contents of Air Filters

Abstract The direct introduction of solid samples (air filters) to the inductively coupled plasma source of an atomic emission spectrometer using a furnace atomizer has been studied. Conditions have been found for the analysis of elements which volatilize with varyling degrees of difficulty. Lead, copper and vandaium compounds retained on glass fibre filters from air pollution studies have been determined. The results are in good agreement with those obtained by means of established sample dissolution/atomic emision methods.