Capabilities of femtosecond laser ablation ICP-MS for the major, minor, and trace element analysis of high alloyed steels and super alloys

Femtosecond laser ablation inductively coupled plasma mass spectrometry was used for the quantification of 23 metallurgical relevant elements in unalloyed, alloyed and highly alloyed steels, and super alloys. It was shown that by using scanning mode ablation with large ablation spot diameters (250μm), stable and representative sampling can be achieved for the majority of elements, except for bismuth and lead. For Bi and Pb up to 46%, temporal relative standard deviation (TRSD) was encountered, whereas for most other elements, the TRSDs were below 10%. Calibration with matrix-matched and non-matrix-matched standards provided similar agreement within the uncertainty of the certified values. However, the non-matrix-matched standard-based quantification was more influenced by interferences rather than ablation- or excitation-related matrix effects. The method was validated using 34 certified reference materials. 52Cr, 51V, or 55Mn were used as internal standards due to the fact that the Fe concentration was not certified for the majority of reference materials. The determined concentrations for major and minor elements indicate that the total matrix internal standardization (100wt.%) is applicable, which requires no knowledge about the steel samples prior to analysis. Figure CRM chips embedded in epoxy resi

A new ICP-TOFMS. Measurement and readout of mass spectra with 30 μs time resolution, applied to in-torch LA-ICP-MS

In-torch LA-ICP-MS was implemented into an in-house-built ICP-TOFMS system. The fast data acquisition capabilities of the new configuration allowed simultaneous multi-element measurement and readout of in-torch LA-ICP-MS signals with 30μs time resolution. The measurements confirmed previously observed fine structures of in-torch generated signals and provided new insights in the dynamic processes in the plasma on a microsecond time scale. The new setup is described in detail and first figures of merit are given. Figure Time dependent multi element signal after laser ablation in the torch of an ICP-TOFMS instrumen

The agglomeration state of nanosecond laser-generated aerosol particles entering the ICP

Fundamental understanding of aerosol formation and particle transport are important aspects of understanding and improving laser-ablation ICP-MS. To obtain more information about particles entering the ICP, laser aerosols generated under different ablation conditions were collected on membrane filters. The particles and agglomerates were then visualised using scanning electron microscope (SEM) imaging. To determine variations between different sample matrices, opaque (USGS BCR-2G) and transparent (NIST SRM 610) glass, CaF2, and brass (MBH B26) samples were ablated using two different laser wavelengths, 193 and 266nm. This study showed that the condensed nano-particles (∼10nm in diameter) formed by laser ablation reach the ICP as micron-sized agglomerates; this is apparent from filters which contain only a few well-separated particles and particle agglomerates. Ablation experiments on different metals and non-metals show that the structure of the agglomerates is matrix-dependent. Laser aerosols generated from silicates and metals form linear agglomerates whereas particle-agglomerates of ablated CaF2 have cotton-like structures. Amongst other conditions, this study shows that the absorption characteristics of the sample and the laser wavelength determine the production of micron-sized spherical particles formed by liquid droplet ejectio

Measurement of isotope ratios on transient signals by MC-ICP-MS

Precise and accurate isotope ratio measurements are an important task in many applications such as isotope-dilution mass spectrometry, bioavailability studies, or the determination of isotope variations in geological or nuclear samples. The technique of MC-ICP-MS has attracted much attention because it permits the precise measurement of isotope compositions for a wide range of elements combined with excellent detection limits due to high ionisation efficiencies. However, the results are based mainly on measurements using continuous sample introduction. In the present study the determination of isotope ratios on various transient signals with a time duration of 30 to 60s has been achieved by coupling high-performance liquid chromatography to a multicollector inductively coupled plasma mass spectrometer. In order to investigate the origin of ratio drifts across the transient signals for this hyphenated technique, measurements with the same standard solutions were also carried out using a flow-injection device for sample introduction. As a result of this application it could be concluded that the main source of the bias in the measured isotope ratios is within the ICP-MS instead of fractionation effects on the chromatographic column material. Preliminary studies on short transient signals of gaseous samples (dry plasma) showed a reverse fractionation effect compared with wet plasma conditions (flow injection and HPLC

Analyte response in laser ablation inductively coupled plasma mass spectrometry

The dependence of analyte sensitivity and vaporization efficiency on the operating parameters of an inductively coupled plasma mass spectrometer (ICPMS) was investigated for a wide range of elements in aerosols, produced by laser ablation of silicate glass. The ion signals were recorded for different carrier gas flow rates at different plasma power for two different laser ablation systems and carrier gases. Differences in atomization efficiency and analyte sensitivity are significant for the two gases and the particle size distribution of the aerosol. Vaporization of the aerosol is enhanced when helium is used, which is attributed to a better energy-transfer from the plasma to the central channel of the ICP and a higher diffusion rate of the vaporized material. This minimizes elemental fractionation caused by sequential evaporation and reduces diffusion losses in the ICP. The sensitivity change with carrier gas flow variation is dependent on m/z of the analyte ion and the chemical properties of the element. Elements with high vaporization temperatures reach a maximum at lower gas flow rates than easily vaporized elements. The sensitivity change is furthermore dependent on m/z of the analyte ion, due to the mass dependence of the ion kinetic energies. The mass response curve of the ICPMS is thus not only a result of space charge effects in the ion optics but is also affected by radial diffusion of analyte ions and the mismatch between their kinetic energy after expansion in the vacuum interface and the ion optic setting

2014 Bunsen-Kirchhoff Award for Analytical Spectroscopy: DASp Deutscher Arbeitskreis für angewandte Spektroskopie

ISSN:1618-2650ISSN:1618-264

Alpha tensor and dynamo excitation in turbulent fluids with anisotropic conductivity fluctuations

A mean-field theory of the electrodynamics of a turbulent fluid is formulated under the assumption that the molecular electric conductivity is correlated with the turbulent velocity fluctuation in the (radial) direction, $\mathbf{g}$. It is shown that for such homogeneous fluids a strong turbulence-induced field advection anti-parallel to $\mathbf{g}$ arises almost independently of rotation. For rotating fluids, an extra $\alpha$ effect appears with the known symmetries and with the expected maximum at the poles. Fast rotation, however, with Coriolis number exceeding unity suppresses this term. Numerical simulations of forced turbulence using the NIRVANA code demonstrate that the radial advection velocity, $\gamma$, always dominates the $\alpha$ term. We show finally with simplified models that $\alpha^2$ dynamos are strongly influenced by the radial pumping: for $\gamma<\alpha$ the solutions become oscillatory, while for $\gamma>\alpha$ they become highly exotic if they exist at all. In conclusion, dynamo models for slow and fast solid-body rotation on the basis of finite conductivity-velocity correlations are unlikely to work, at least for $\alpha^2\Omega$ dynamos without strong shear.Comment: 10 pages, 8 figures, to be published in A

Alpha tensor and dynamo excitation in turbulent fluids with anisotropic conductivity fluctuations

A mean-field theory of the electrodynamics of a turbulent fluid is formulated under the assumption that the molecular electric conductivity is correlated with the turbulent velocity fluctuation in the (radial) direction, (Formula presented.). It is shown that for such homogeneous fluids a strong turbulence-induced field advection anti-parallel to (Formula presented.) arises almost independently of rotation. For rotating fluids, an extra (Formula presented.) effect appears with the known symmetries and with the expected maximum at the poles. Fast rotation, however, with Coriolis number exceeding unity suppresses this term. Numerical simulations of forced turbulence using the nirvana code demonstrate that the radial advection velocity, (Formula presented.), always dominates the (Formula presented.) term. We show finally with simplified models that (Formula presented.) dynamos are strongly influenced by the radial pumping: for (Formula presented.) the solutions become oscillatory, while for (Formula presented.) they become highly exotic if they exist at all. In conclusion, dynamo models for slow and fast solid-body rotation on the basis of finite conductivity–velocity correlations are unlikely to work, at least for (Formula presented.) dynamos without strong shear