Jon C. Van Loon

A critical study of the application of graphite-furnace non-flame atomic absorption spectrometry to the deter-mination of trace base metals in complex heavy-matrix sample solutions

Abstract Because of the extravagant claims made for the usefulness of non-flame atomic absorption spectroscopy, a critical evaluation of its performance in heavy matrix solutions, for selected trace heavy metals, was made. Studies of physical and chemical interference problems are presented for a range of inorganic and organic matrices. Often quoted remedies (e.g. selective volatilization, standard addition etc.) for solution of the more serious problems were found to be of little help in most cases. The influence of variables such as nature and flow rate of purge gas, ashing temperature and atomization temperature are also evaluated. Analyses for Cd, Cu, Pb, Zn, Ni, Co were done on samples by flame and nonflame methods in high solids solutions. While there appears to be an advantage to the non-flame method in dealing with sample solutions of high organic content, no advantage is apparent for either technique with highly inorganic matrices.

Inductively Coupled, Plasma Source Mass Spectrometry - A New Element/Isotope Specific Mass Spectrometry Detector for Chromatography

Abstract A new mass spectrometry detector for chromatography is described. It is element/isotope specific. The interfacing of GC with the detector is very simple, consisting of a short (0. 5m) stainless steel tube. Oxygen gas (about 20% of total sample gas flow) must be injected, into the GC effluent entering the torch, to prevent carbon buildup on the torch. Three pentylated tin compounds (Me3SnPe, Me2SnPe2 and MeSnPe3) were separated and determined using the system. Although detection limits (ngs) achieved in this preliminary work were worse by over 2 orders of magnitude compared to state-of-the-art electrothermal atomic absorption detection, the approach holds much promise for the future in environmental/clinical metal organic species investigations.

Atomic absorption spectroscopy as a detector for the gas chromatographic study of volatile selenium alkanes from Astragalus racemosus

Abstract A simple, inexpensive ( Astragalus of which two were readily shown to be the alkanes dimethyl selenide and dimethyl diselenide. Diethyl selenide was not detected.

Determination of tin in environmental samples by graphite furnace atomic absorption and inductively coupled plasma-mass spectrometry

SummaryMethods for the determination of “total” Sn in environmental samples (waters, animal tissue, plant material, sediments and coal fly ash), by graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma mass spectrometry (ICP-MS) have been developed and evaluated.Noble metals (Ag, Au, Pd, Pt, Rh) under reducing conditions were studied as matrix modifiers for the determination of Sn by GFAAS. The maximum ashing temperature (1400°C), highest sensitivity and the best absolute detection limit (4 pg) were achieved when Pd was used in the presence of hydroxylamine hydrochloride. The achievable sensitivity depended strongly on the chemical composition of the matrix.Both GFAAS and ICP-MS appeared to be equally sensitive techniques for the direct determination of Sn in waters, though ICP-MS was a more convenient and sensitive technique for the determination of Sn in digested biological and geological materials.

Dry-chlorination inductively coupled plasma mass spectrometric method for the determination of platinum group elements in rocks

A dry-chlorination procedure has been developed for use in the determination of low concentrations of platinum group elements (PGE) and Au in rock pulps. The PGE and Au, present as native metals, natural alloys and as PGE-(or Au-) bearing sulfide group minerals, are converted by dry-chlorination into PGE (or Au) sodium salts. These salts are dissolved in weak HCl. The solutions are analysed for PGE and Au content by inductively coupled plasma mass spectrometry (ICP-MS). Tests on three reference rock pulps [diluted South African Bureau of Standards Reference Material (SARM)-7 Platinum Ore; diluted INCO S-1800; Nevada Bureau of Mines (NBM) 6a Stillwater] and one gabbro rock showed that the dry-chlorination–ICP-MS method produced results that were usually comparable to, and often better than, fire assay techniques. Reagent contamination was extremely low (Pt⩽1 ng g–1; other PGE and Au⩽0.2 ng g–1). The recoveries of PGE obtained by dry-chlorination–ICP-MS were often >90%.

Determination of organic forms of mercury and arsenic in water and atmospheric samples by gas chromatography-atomic absorption

ZusammenfassungDie Bestimmung von Dimethylquecksilber, Methylquecksilber, Ethylquecksilber, Dimethylarsin und Methylarsin in Wasser und atmosphärischen Proben wurde untersucht. Die Verbindungen wurden aus Wasser mit Hilfe eines Benzol-Toluol-Gemisches extrahiert, falls erforderlich eingedampft und durch Gas-Chromatographie mit AAS-Detektion analysiert. Zur Verwendung kam eine 45-cm-Tenax-Säule. Folgende Nachweisgrenzen wurden gefunden: 4 ng Hg in Dimethyl- und Methylquecksilber, 5 ng Hg in Ethylquecksilber und 25 ng As in Dimethyl- und Methylarsin je Liter Wasser. 12–45 bzw. 7–l5 ng Hg l−1 Methyl- bzw. Ethylquecksilber wurden in natürlichem Wasser und Schnee von Ontario bestimmt. Die Menge an Methylarsin schwankte von 40 bis 90 ng Hg l−1. Dimethylquecksilber und Dimethylarsen wurden nur im Humber gefundenSummaryA study of the determination of dimethylmercury, methylmercury, ethylmercury, dimethylarsine and methylarsine in water and in atmospheric samples was carried out. The studied compounds were extracted from water by a benzene-toluene mixture, evaporated if necessary and analyzed by gas chromatography with atomic absorption spectrometry as a detector. A 45 cm column packed with Tenax was used. The detection limits of the procedure were: 4 ng Hg in dimethylmercury and methylmercury, 5 ng Hg in ethylmercury and 25 ng As in dimethyl and methylarsine in 1 l water. Methylmercury and ethylmercury were detected in Ontario natural waters and snow at 12–45 and 7–15 ng Hg l−1 respectively. The level of methylarsine varied from 40 to 90 ng l−1. Dimethylmercury and dimethylarsine were detected only in the Humber River.

Mercury contamination of vegetation due to the application of sewage sludge as a fertilizer.

Abstract The mercury content of vegetation grown on sludged and control plots is given. Both washed and unwashed specimens are tested. Material analysed is, leaves and seeds of wild barley and quack grass; tomato roots, plants and fruit; bean roots, plants and pods; carrot roots and tops and lettuce leaf. No significant increase in mercury levels for washed plant material grown on sludged plots was noted except in the case of tomato fruit which showed levels up to 50 times higher compared to specimens from unsludged plots. Surface contamination of vegetation by mercury containing dusts and soils can cause elevated levels in unwashed or poorly washed material.

Environmental and biological samples analyzed by inductively coupled plasma emission spectrometry

A number of closely related acid digestion procedures are proposed for the accurate analysis of animal tissue, plant tissue, sediment and particulate samples. A closed teflon vessel is employed to reduce contamination and to speed up digestion. Procedures which minimize evaporations should be employed where applicable. Hydrofluoric acid is essential when plant tissue, sediment and particulate material are to be dissolved. Accuracy and precision is assessed using standard reference samples.

An evaluation of the use of halogen and water abundances in efforts to distinguish mineralized and barren intrusive rocks

Abstract Analysis of the chlorine, fluorine and water content of approximately 200 samples from a total of fourteen mineralized and ten barren intrusive rocks from the Caribbean and Central America indicates that abundances of these constituents fail to distinguish mineralized rocks from barren rocks. Variations in background abundances arise from the increase in halogen content of potassium-rich rocks and from the depletion of halogens in altered and porphyritic rocks. A particularly well developed potassium-fluorine covariance is observed in tin-bearing granites, but such a covariance cannot be used to distinguish intrusive rocks associated with porphyry copper mineralization.

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.