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A new method has been developed for the accurate and precise measurement of sulfur isotopes (32S, 33S, 34S) in solids on a scale down to 80–100 μm by laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). The method was developed independently on two different sets of instrumentation, both of which give equivalent results with comparable accuracy and precision. The first instrumental set-up utilizes Xe gas in a hexapole collision and reaction cell for interference attenuation coupled with a mass discrimination correction by external normalization using a nebulised vapour of 37Cl/35Cl standard solution. The second employs high mass resolution by sector field mass spectrometry to avoid the interfering O2+ isobars with a 30Si/29Si standard aerosol for external normalization. The external isotope mass discrimination correction was applied using the exponential law and was further calibrated for both sets of instrumentation by linear interpolation in a sample–standard bracketing method. Mean δ34SV-CDT and δ33SV-CDT show excellent agreement (within analytical error, typically 0.6 and 1.5‰, respectively) with compiled data for IAEA-S series AgS standard reference materials. Results for NIST SRM 127 (sulfate) were less accurate when calibrated against the IAEA-S series sulfides, whilst significant and consistent deviations in accuracy of up to 3‰ were observed in both sets of instrumentation for Soufre de Lacq SRM sulfur. Such generic matrix effects may be widespread in LA-ICP-MS due to differential ablation rates, particle formation, particle transport efficiency and ionization efficiency in an argon plasma.

The chemical and phase compositions of particles produced by laser ablation (266 nm Nd:YAG) of silicate NIST glasses and zircon were studied by SIMS and HR-TEM techniques. The data suggest that the formation of phases of different mineralogy and/or chemical composition from the original sample at the ablation site can result in elemental fractionation (non-stoichiometric sampling) in material delivered to the ICP-MS for quantitative analysis. Evidence of the element fractionation is preserved in chemically zoned ejecta deposited around the ablation pit. The chemical composition and mineralogy of particles varies with particle size so that the efficiency of transport of particles also plays a role in elemental fractionation. During the first 250 pulses in a typical ablation experiment using a 266 nm laser, particle sizes are mainly

The isotopic composition of Fe in iron meteorites and iron sulfides was studied with a UV laser (213 nm wavelength) and a high-mass resolution multicollector-ICP-MS. The long term reproducibility of Fe isotopic measurements was 0.16 and 0.21‰ (2 standard deviations) for δ56Fe and δ57Fe, respectively, i.e., a factor of ∼2 worse than conventional solution analysis. At present the major limitations of precision and accuracy in the laser ablation technique are instrumental mass discrimination (2.0–4.9% per amu) and laser-induced fractionation (up to 4‰ during a single analysis) of Fe isotopes. Laser ablation of iron metal and iron sulfides produces two types of particles: (1) coarse (50–600 nm) spherical and crystalline particles that are isotopically heavier than (2) fine (2–7 nm) amorphous particles. Differential transport of the two types of particles to the ICP can compromise the accuracy of Fe isotope measurements by laser ablation MC-ICP-MS. Despite lower precision compared with solution MC-ICP-MS analysis, the laser ablation technique is capable of resolving Fe isotopic variations between seafloor and sub-seafloor hydrothermal sulfides, and between kamacite and taenite alloys that are commonly present as thin lamellae in iron meteorites. The most important applications of the technique will be for the analysis of small samples where the textural context of the analysed objects is important for the interpretation of Fe isotopic data.

Data on elemental fractionation of alkali elements during laser ablation ICP-MS analysis of silicate reference glasses (NIST-610, BCR-2G, alkali element-doped andesite glasses) and crystalline mineral albite (NaAlSi3O8) are reported. Laser ablation ICP-MS and SIMS were used to determine differences in sample composition before and after laser interaction with the samples. The fractionation trends of the alkali elements are different from those of other lithophile elements, such as Ca and the rare earth elements (REEs). The rate of fractionation varies for different sample matrices and for different alkali elements in the same matrix. Data from SIMS analyses of the ejecta blanket deposited adjacent to the laser ablation crater in silicate NIST-610 glass and crystalline albite suggest a matrix dependent fractionation of alkali elements for different particle size fractions in the ablated aerosol. The extent of fractionation varies for different alkali elements and is independent of their ionic radii. Ion probe depth profiling into the bottom of laser craters showed laser ablation-induced chemical changes in the sample that involved alkali elements and major matrix elements including Si and Ca. This suggests that a combination of thermally-driven diffusion and size-dependent particle fractionation are responsible for the observed fractionation of alkali elements during laser ablation of silicate samples.