Kym E. Jarvis

Bioavailability of Nanoscale Metal Oxides TiO2, CeO2, and ZnO to Fish

Nanoparticles (NPs) are reported to be a potential environmental health hazard. For organisms living in the aquatic environment, there is uncertainty on exposure because of a lack of understanding and data regarding the fate, behavior, and bioavailability of the nanomaterials in the water column. This paper reports on a series of integrative biological and physicochemical studies on the uptake of unmodified commercial nanoscale metal oxides, zinc oxide (ZnO), cerium dioxide (CeO(2)), and titanium dioxide (TiO(2)), from the water and diet to determine their potential ecotoxicological impacts on fish as a function of concentration. Particle characterizations were performed and tissue concentrations were measured by a wide range of analytical methods. Definitive uptake from the water column and localization of TiO(2) NPs in gills was demonstrated for the first time by use of coherent anti-Stokes Raman scattering (CARS) microscopy. Significant uptake of nanomaterials was found only for cerium in the liver of zebrafish exposed via the water and ionic titanium in the gut of trout exposed via the diet. For the aqueous exposures undertaken, formation of large NP aggregates (up to 3 mum) occurred and it is likely that this resulted in limited bioavailability of the unmodified metal oxide NPs in fish.

An assessment of dissolution techniques for the analysis of geological samples by plasma spectrometry

Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and ICP-mass spectrometry (ICP-MS) are being used increasingly for the analysis of a wide range of geological materials. The rapidity of these multi-element techniques results in sample dissolution being the limiting step in sample through-put. This study critically evaluates results obtained from two routinely used sample preparation methods: LiBO2 fusion and open-vessel HF-HClO4 digestion, and compares them with data obtained from microwave-heated, sealed-vessel, acid digestion. Detailed procedures are given for each method. Nine standard reference materials (SRM) were used in the comparison. Selected major and trace elements were determined by ICP-AES to assess the general effectiveness of each dissolution procedure, and 24 trace elements plus the 14 rare-earth elements (REE) were determined by ICP-MS. Trace elements determined by both methods show good agreement. The accuracy and precision of the results were dependent on the dissolution technique and the mineralogy/composition of the material. LiBO2 fusion resulted in complete recovery of major and many minor elements including Cr, Hf and Zr, but the volatile elements Pb, Sb, Sn and Zn were lost. The open acid and the microwave digestions produced similar results and proved suitable for the determination of most elements in most materials. Microwave digestion has the advantage of shorter digestion times and uses smaller volumes of reagents. The accuracy of Zr and Hf data was dependent on the sample type. Cr showed a low recovery by open acid attack and this was only partially improved by microwave digestion. Results indicate that a combination of sample preparation techniques is required if quantitative data are sought for the full range of elements studied here.

Inductively coupled plasma mass spectrometry: A new technique for the rapid or ultra-trace level determination of the rare-earth elements in geological materials

Abstract New techniques for the determination of the rare-earth elements (REE) and Y in geological samples by inductively coupled plasma-mass spectrometry (ICP-MS) are described. Samples were prepared using conventional rock dissolution procedures. The accuracy and precision of the methods were assessed by the analysis of eight standard reference materials including two feldspar separates. The REE and Y were measured directly in a solution traditionally prepared for routine trace-element analysis down to 10 × chondritic abundances. Employing separation and preconcentration by ion exchange, levels down to 0.01 × chrondrite can be measured with relatively good precision and accuracy.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS): a rapid technique for the direct, quantitative determination of major, trace and rare-earth elements in geological samples

Abstract A Nd:YAG laser in fixed-Q (free-running) mode coupled to an inductively coupled plasma mass spectrometer was used to directly analyse pressed powder pellets of seven well-characterised silicate rock reference materials (AGV-1, BIR-1, DNC-1, G-2, NIST 2704, SCo-1 and W-2). The multielement limits of detection (LOD) were in the range 0.05–13 μ g−1 but with a majority of values better than 0.1 μ g−1. Using a narrow range scan LOD for the rare-earth elements (REEs) were between 11–84 ng g−1. Relative responses for the major elements indicate that the chemistry and mineralogy of individual rock samples influence the ablation behaviour, and that samples with very similar chemical and mineralogical compositions exhibit similar elemental responses. The accuracy of major-element determinations, for the materials studied, was generally better than ± 5% with a precision of 10% RSD. First-row transition elements, incompatible elements and, in particular, REEs displayed a high degree of accuracy, with precision of generally

Assessment of Dowex 1-X8-based Anion-exchange Procedures for the Separation and Determination of Ruthenium, Rhodium, Palladium, Iridium, Platinum and Gold in Geological Samples by Inductively Coupled Plasma Mass Spectrometry

Synthetic multielement solutions of the platinum group metals (PGE: Ru; Rh; Pd; Ir; Pt) and gold, with analysis by ICP-AES and ICP-MS, have been used to study the behaviour of the precious metals on Dowex 1-X8 resin. Simple solutions of precious-metal chlorocomplexes showed near-complete adsorption (>99%) of most elements, and only minor breakthrough of Ru and Ru (≈5%). Solutions pre-treated with acid mixtures typically used to decompose geological samples, demonstrated that perchloric acid adversely affects the adsorption of the PGEs on the resin. Solutions treated with HF–HNO 3 –HCl maintained good retention of Ir, Pt, Au (>99%), Pd (>94%) and Ru (>90%), but displayed significant loss (up to 40%) of Rh. A two-step procedure was necessary to elute the precious metals from the resin: 0.3 mol l - 1 thiourea prepared in 0.1 mol - 1 HCl removed Ru, Pd, Pt, Au, and some Rh: 12 mol l - 1 HCl eluted remaining Rh and all Ir. Recoveries ranged from 50 to 100%. At low levels, the determination of PGE and Au in the thiourea fraction by ICP-MS was compromised by high levels of total dissolved solids (TDS), which necessitated dilution of the eluate prior to analysis. The TDS was reduced by decomposing thiourea with HNO 3 and removing SO 4 2 - by precipitation of BaSO 4 , but this led to lower and more erratic results, and increased contamination. An assessment of the optimised procedure employing geological reference materials PTM-1, PTC-1 and SARM7, indicated that acceptable results should be attainable for ICP-MS determination of most elements in geological samples containing high concentrations (>1 µg g - 1 ) of the PGE, for which decomposition of thiourea is unneccessary. The addition of a decomposition step led to low recovery of all elements except Ir, which was present entirely in the HCl eluate. The method is viable for the determination of Ir in a range of geological materials, but modifications will be required if it is to be extended to the other precious metals.

REE composition of an aqueous magmatic fluid: A fluid inclusion study from the Capitan Pluton, New Mexico, U.S.A.

Abstract The REE content of aqueous magmatic-derived fluids trapped in fluid inclusions, has been determined by ICP-MS after crush-leach extraction of the fluids in 4 samples. The total REE concentration varies between 200 and 1300 ppm and is dominated by the LREE, especially La, Ce and Nd. Fluids were released at different times from a melt, which changed composition as it underwent fractional crystallisation, and this is reflected in the concentration of REE in solution. Early formed quartz-fluorite veins, hosted by granophyre, contain the highest concentration of REE, and appear to be in equilibrium with aplite melt from which the fluid was inferred to have been derived since calculated fluid/melt distribution coefficients are in broad agreement with experimentally derived values. Variation in the REE content of the fluids is independent of salinity which remains constant at ∼ 80 wt% total salts. Later veins, hosted by aplite, contain fluid derived from a porphyritic melt and have lower REE concentrations, reflecting the greater incorporation of REE into mineral phases crystallising from the melt: titanite and allanite occur in these later veins. REE mineral/fluid distribution coefficients have been calculated for these minerals and show there is a strong preference for REE to partition into the minerals.

Plasma spectrometry in the earth sciences: techniques, applications and future trends☆

Abstract Plasma spectrometry is one of the most popular and versatile techniques for the analysis of geological and environmental samples, including rocks and minerals, waters, dust, vegetation, soils, sewage sludges and sediments. Inductively coupled or direct current argon plasmas are used as emission sources in ICP-and DCP-atomic emission spectrometry (ICP-AES, DCP-AES); an ICP provides an ion sources in ICP-mass spectrometry (ICP-MS). Reviews of the two plasma sources, sample introduction systems, and the instrumental and analytical performances of emission and mass spectrometers, demonstrates the superiority of higher-temperature, ICP-based systems. ICP-AES and ICP-MS are characterised by wide linear responses of more than five orders of magnitude. They are rapid and highly cost-effective multi-element techniques which can theoretically determine over 70 elements in

A critical evaluation of two sample preparation techniques for low-level determination of some geologically incompatible elements by inductively coupled plasma-mass spectrometry

The accurate measurement of low levels of highly incompatible elements is an essential requirement for many geochemical studies. The elements of interest vary, depending on the rock suite under investigation, but frequently include the heavier elements, e.g. Pb, Zr, Hf, U, Th, Nb, Ta and the REE. Some of these elements are partitioned into resistant mineral phases, which can most easily be brought into solution using a fusion technique. This work describes a method for the determination of low levels (< 1 μg g−1 in the rock) of incompatible elements using inductively coupled plasma-mass spectrometry (ICP-MS). Twenty-three standard reference materials were prepared using both an open acid digestion and a lithium metaborate fusion. Calibration of the ICP-MS instrument was achieved using simple aqueous solutions and analysis times were short, typically < 1 min. per analysis. The accuracy of the data is dependent on the particular element of interest. Y, Th, U and the REE can be measured with good accuracy (typically better than ± 5%) in a range of silicate and carbonate matrices, both in samples brought into solution by acid digestion and fusion. Data for Zr, Hf, Ta, Nb and Pb are more complex to interpret. Pb is lost from fused samples while some other elements display inaccurate data, probably due to dissolution problems with resistant mineral phases.

Determination of the platinum-group elements in geological materials by ICP-MS using microwave digestion, alkali fusion and cation-exchange chromatography

The available instrumental methods for platinum group element (PGE: Ru, Rh, Pd, Os, Ir, Pt) and gold (Au) determinations are reviewed. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and ICP-mass spectrometry (ICP-MS) enable rapid, multi-elemental analysis, their instrumental and analytical characteristics being discussed here. The suitability of ICP techniques to quantitatively determine the PGEs + Au is demonstrated. The detection limits by ICP-AES range from 6 to 29 ng.mL[sup]-1, while those for ICP-MS range from 0.3 to 0.22 ng.mL[sup]-1, for the individual PGEs + Au. A digestion step is generally required prior to the analysis of geological materials by ICP-AES and/or ICP-MS. Digestion procedures are reviewed, with particular attention to the new method of microwave digestion. A comparative study of three digestion methods was undertaken, a range of well-characterised rock reference materials being used to evaluate open acid digestion, microwave acid digestion and alkali fusion procedures. The precision and accuracy of results obtained by ICP-AES and ICP-MS for 46 elements demonstrates that no single digestion method is universally applicable. It is concluded that the best digestion procedure for PGE-bearing materials is a combination of microwave acid digestion followed by a fusion of the residue. Such a method was developed and its suitability is demonstrated using reference materials containing high levels of the PGEs + Au, which enable their direct determination by solution ICP-MS. Even with the superior sensitivity of ICP-MS, low concentrations of the PGEs + Au in most geological materials preclude the quantitation of unseparated samples. Separation methods which have been used (fire assay, coprecipitation, ion exchange, solvent extraction, distillation) are reviewed. Two ion-exchange methods were developed to separate the PGEs + Au from their associated matrix elements allowing their preconcentration prior to analysis. An anion-exchange method can be used in conjunction with ICP-MS for the separation and determination of ≥1 ng.g[sup]-1 Ir and> 1 [mu]g.g[sup]-1 Ru, Rh, Pd, Pt or Au. A cation-exchange ICP-MS procedure can be used to determine the PGEs at a wider range of concentrations. An evaluation using all the available PGE reference materials showed good agreement with reference values in most instances. Stable isotopes were used to evaluate this method and the results confirm that quantitative results may be obtained. The cation-exchange procedure can be scaled-up to larger samples thus enabling the determination of < 1 ng.mL[sup]-1 of individual PGEs. This is demonstrated using 5 g sub-samples and guidelines are given for further increases in sample size. Slurry nebulisation ICP-MS was developed for the determination of the PGEs + Au in solid samples without a prior digestion stage. An assessment of the method using reference materials demonstrated that quantitative results may be obtained for all seven PGEs + Au at levels above 50 to 200 ng.g[sup]-1 (depending on the element). This method is ideally suited to the routine analysis of mineralised samples or where only small sample sizes are available.

Determination of platinum, palladium, ruthenium and iridium in geological samples by isotope dilution inductively coupled plasma mass spectrometry using a sodium peroxide fusion and tellurium coprecipitation

A method was developed for the determination of Ru, Pd, Ir and Pt in geological samples by isotope dilution inductively coupled plasma mass spectrometry. After fusion of the sample with sodium peroxide, the platinum group elements were preconcentrated by Te coprecipitation. Results obtained for the reference materials WGB-1, TDB-1, UMT-1, WPR-1, WMG-1 and SARM-7 are in excellent agreement with the recommended values for elements above the detection limit level of 0.3–2.0 ng g–1(whole rock). Although the method used only 0.5 g of sample, no errors were found that could be associated with sample inhomogeneity effects in the analysis of the above reference materials. Further measurements indicated that the technique could be extended to the determination of Rh and Au by external calibration.