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.

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.

Overview of analytical methods for elemental speciation.

This paper describes a selection of the major developments in the field of analytical methodology for elemental speciation over the period from January 1986 to December 1990. Methods for a number of elements will be highlighted. Judging by the number and diversity of published reports, there has been increasing interest and activity in the development of new and modified analytical methods. Further, it is very encouraging to observe the number of papers concerned with the accuracy and precision of such analytical methods, and with comparisons between two or more methods. Among electrochemical methods of analysis, anodic stripping voltammetry has provided an important basis for measurements of concentrations of labile metals in aqueous media. The fastest growing area of method development is the coupling of separation methods, usually chromatography, with a single- or multi-element detector. Most importantly, inductively coupled plasma mass spectrometry has recently been described as a very sensitive, multi-element detector. The success of a 'coupled' method is greatly dependent on a suitable interface. Several papers have been published recently describing useful interfaces. Chemical extraction procedures continue to occupy an important place. Applications of analytical elemental speciation methods have included environmental, biological, clinical and geological samples. A number of methods for elements most frequently studied will be discussed.

Release of metal ions from dental implant materials in vivo: determination of Al, Co, Cr, Mo, Ni, V, and Ti in organ tissue.

Little is known of the release of trace elements in vivo from dental implant materials. Conflicting data have been reported in the literature as to the levels of trace elements released and their potential consequences, mainly because of sampling and analytical methodological errors. In this study methods for average concentration levels of Al, Cr, Co, Mo, Ni, Ti, and V in organs were developed using rabbit tissue from an in vivo implantation study. At least 50% of the brain, liver, lung, kidney, and spleen were taken minimizing contamination. The tissue was homogenized by cryogenic milling at LN2 temperature and then freeze-dried. Samples were digested in nitric acid and hydrogen peroxide using microwave energy. Standard reference materials were utilized for quality control. One liver sample was analyzed 10 times to assess the method precision. Absorbance values in blanks, standards, and test samples were measured using a Varian GTA 95 graphite furnace and 875 spectrophotometer. Very satisfactory method precision and quality control were recorded. Low or very low levels of the trace elements were found in the various organs.

Determination of chromium, cobalt and molybdenum in synovial fluid by GFAAS.

An artificial knee joint made of a cobalt alloy (Cr 27-38%, Mo 5-7%, others 9%, Co balance) failed in an orthopaedic patient with severe tissue reaction. Samples of synovial fluid and blood were analyzed for cobalt, chromium and molybdenum concentration using graphite furnace atomic absorption spectrophotometry (GFAAS). NIST SRM 909 Human Serum containing 91.3 micrograms/L chromium was used as the Cr Standard. To obtain reliable values for cobalt and molybdenum, three different independent analytical methods were employed to analyze each sample: 1) dilution of the samples with Triton TX-100 solution, followed by GFAAS; 2) microwave decomposition of the samples, followed by GFAAS; 3) classic nitric-perchloric acid decomposition of the samples, followed by GFAAS. The two decomposition methods were used to control the accuracy of the dilution method. The results showed that the non-decomposition method gave comparable results to the decomposition techniques for analysis of synovial fluid and blood. The data revealed that the patient had elevated levels of Co, Cr and Mo in both synovial fluid and blood with the values being 2-3 orders of magnitude higher in the synovial fluid from the affected knee.

The determination of Al, Cr, Co, Fe, and Ni in whole blood by electrothermal atomic absorption spectrophotometry.

Procedures for the determination of aluminum, chromium, cobalt, nickel, and iron in whole blood are presented and discussed. Chromium, cobalt, nickel, and iron were determined from one sample after decomposition of the blood with a mixture of nitric and perchloric acids. A graphite furnace was used for the determination of chromium, cobalt and nickel, and flame AAS was used for iron. The determination of Al was done from separate samples by GFAAS after dilution with 1% Triton TX-100. The normal concentration of these elements was measured in rabbit and dog blood.

A critical review of atomic absorption, spectrochemical, and x-ray fluorescence methods for the determination of the noble metals--II.

The review is a continuation of the initial reviews and covers the period of abstracting up to and including April, 1967. Work on the atomic-absorption determination of noble metals is also included.

Separation and accurate determination of iron and aluminium in a single sample of silicate rock.

A procedure for the separation and subsequent determination of iron and aluminium in silicate samples is given. The anion-exchange separation of iron(III) from vanadium was studied under the conditions of rock analysis. The salt content of the sample solution and the applicability of resins were studied to determine the optimum conditions for the separation of iron and aluminium. The proposed procedure was tested by determining iron and aluminium in the Geological Standards S1 and W1.