J.C. Van Loon

The determination of all the platinum group elements and gold in rocks and ore by neutron activation analysis after preconcentration by a nickel sulphide fire-assay technique on large samples

Abstract The noble metals are inhomogeneously distributed in sulphide ores and their host rocks. It is therefore necessary to analyse large sample sizes to obtain representative analyses. A nickel sulphide fire assay technique has been adapted to extract the noble metals from a large sample size (50 g) into a nickel sulphide button. Subsequently the fire assay button is dissolved in hydrochloric acid and the solution is filtered. The noble metal residue retained on the filter paper is analysed quantitatively by i.n.a.a. techniques. This method is rapid, relatively inexpensive and has better sensitivities for all the noble metals than other analytical techniques.

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.

A study of the atomic absorption determination of some important heavy metals in fertilizers and domestic sewage plant sludges.

Abstract An atomic absorption method is described for the rapid analysis of sewage sludges and processed sewage fertilizers. Extensive data is given to allow an evaluation of the reliability of the method. Results are given for the analyses of sludge and fertilizer samples to show the surprisingly high levels of metals in some of these materials.

Determination of alkyl lead compounds in air by gas chromatography and atomic absorption spectrometry

Abstract Alkyl lead compounds are condensed from a 70-l street air sample in a series of four traps at-72°C, separated by gas chromatography and determined by atomic absorption spectrometry with electrothermal atomization. Total atmospheric alkyl lead averaged 14 ng Pb m -3 . Vehicular exhaust fumes are an insignificant contributor to this total. Tetraethyllead, the only alkyl lead compound used in southern Ontario gasoline, is unstable in air. Besides decomposing, it reacts to give other alkyl lead compounds, which can be determined by the technique described. Evaporation of gasoline is almost exclusively the source of alkyl lead compounds in street air.

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.

Occurrence of tetraalkyllead compounds in the aquatic environment.

Fish, marine vegetation, bottom sediment, and water samples taken from various lakes and rivers in Ontario, Canada, were analyzed for the presence of tetraalkyllead compounds. Experimental materials and methods are described. Of all 107 fish samples analyzed, 17 samples contained tetraalkyllead compounds. There were no detectable amounts of tetraalkyllead in water, vegetation, or sediment, although in some cases hexane extractable lead was present. Results indicate that: there is no relationship between species and size of fish and tetraalkyllead concentration; tetraalkyllead is found in fish from various lakes and rivers in Ontario; the type of tetraalkyllead varied in different locations; and the concentration of tetraalkyllead is generally low, representing less than 10% of the total lead. (10 references, 1 table)

A study of atomic absorption and atomic fluorescence atomization systems as detectors in the gas chromatographic determination of lead

Abstract The suitability of various atomic absorption and atomic fluorescence atomizing systems connected to a gas chromatograph is compared for the determination of alkyl lead compounds. An electrothermally heated graphite tube gives the highest sensitivity but quartz tubes heated either in an air-acetylene flame or by electrical resistance wire provide adequate sensitivity for most applications. A “solvent peak” absorption thought earlier to be due to organic molecular absorption of radiation at the lead wavelength was shown to be due to deposition and remobilization of lead.

Cold Vapor Atomic Absorption determination of mercury by Flow Injection Analysis using a Teflon membrane phase separator coupled to the absorption cell

Abstract A Flow Injection Analysis (FIA) procedure for the determination of trace amounts of mercury by the Cold Vapor Atomic Absorption (CVAA) method is presented. In order to make efficient use of the FIA technique, a new flow cell was developed to permit a rapid separation of elemental mercury from the carrier solution. The design of this device is based on the permeability of Hg 0 in commercially available Teflon (PTFE) tape, which acts as a membrane phase separator. The calibration curve is linear up to 70 ng.ml −1 ( A = 0.005 + 0.008 Hg(ng.ml −1 ); r = 0.9996) using a 15-cm open cell approach, with a detection limit of 1.4 ng. ml −1 (0.66 ng of mercury), considering a signal to noise ratio of three. The standard deviation is s = ±0.004 absorbance units, calculated at a level of 50 ng.ml −1 of Hg 2+ . The sampling rate was 110 samples per h.

Development of a procedure for studies of the chromium(III) and chromium(VI) contents of welding fumes

A method for speciation studies of chromium in welding fumes is described. Separation of chromium(III) and chromium(VI) in aqueous extracts of welding fumes is obtained by using anion- and cation-exchange resins. Atomic absorption spectrometry is used for quantification. At pH 3–5, there is no loss of chromium(III) as the hydroxide nor reduction of chromium(VI) by iron(II). Two types of welding fumes were studied: for ESAB OK 67–52 and AROSTA 316 L fumes, 57 and 91%, respectively, of the total chromium content was water-soluble; the total chromium contents were 5.9 and 4.4%, respectively. Chromium(III) was not detected in the aqueous extracts of either type of fumes (< 0.010 μg ml-1 of extract).

The Rapid Determination of Fluoride in Mineral Fluorides Using a Specific Ion Electrode

Abstract A rapid method for the direct determination of fluoride, not requiring a prior separation of fluoride by distillation, is given. Fluoride results differing from the calculated up to approximately 5% were obtained on samples of Fluorite, Cryolite, Topaz, Chiolite and Matlockite.