Development of a fast laser ablation-inductively coupled plasma-mass spectrometry cell for sub-µm scanning of layered materials

Performance data are reported for a commercially available laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) setup, equipped with a custom-made cell. The low dispersion ablation cell and the connecting tubing achieve a 99% washout of the aerosol in similar to 6 ms, enabling separated pulse responses at frequencies up to 200-300 Hz. In addition, the cell employed supports a post-acquisition methodology for the deconvolution of overlapping ablation positions in scanning mode by an iterative Richardson-Lucy algorithm. This enables correction of the distortion in the scan profile upon traversing layers with dimensions below the physical size of the laser beam. By overlapping the ablation positions of a 1 mu m diameter laser beam, a lateral resolution in the order of 0.3 +/- 0.1 mu m was demonstrated for scanning of mu m-sized layers in high capacitance multi-layer ceramic capacitors

Insights into the secondary glass production in Roman Aquileia: A preliminary study

A set of 29 glass shards, selected from numerous ones recovered in 2017 in Aquileia (NE Italy), was studied to provide evidence of local glass production for that specific area in antiquity. These shards can be dated between the 1st and the 4th century AD. The chemical composition of glass samples was obtained using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) that enables to quantify the concentration of major, minor, and trace elements needed to investigate provenance and compositional groups and sometimes to suggest a chronological frame of the samples. To ensure that the samples are homogeneous enough to perform accurate quantification, some of them were also analysed by instrumental neutron activation analysis (INAA). Most of the chunks, working wastes, and artefact shards considered in this work exhibited similarities among them in terms of composition, which likely indicates that glass working activities were practised at the site of recovery. The analyses demonstrated the presence of both recycled glass and primary glass. Interestingly, the compositional data of raw primary glass point to both Syro-Palestinian and Egyptian regions as sourcing areas, confirming the role of the Roman city of Aquileia as a network node for the trade of goods. In addition, some particularly coloured glass fragments showed a composition typical of glass produced starting from the 1st or 2nd century AD, requiring specific types of furnaces and procedures for its manufacture, and suggesting the possibility of local highly-specialised production. The preliminary results of this work strengthen the hypothesis that Aquileia was a thriving centre, either for working primary glass or for glass recycling and production of objects with particular colours

Angular resolution dependency in 2D LA-ICP-MS mapping : the case for low-dispersion laser ablation cells

In LA-ICP-MS imaging mostly lateral resolution is considered, but this work will show that linear artifacts with an angular aspect to the line scan direction may have a different spatial resolution, depending on the blur introduced by LA sampling and aerosol washout/transfer. This implies that upon scanning an irregularly shaped artifact, the spatial resolution in different locations may vary, the severity of which will be a function of the amount of "smearing" induced by the LA-ICP-MS system, invariably related to the design of the LA cell and aerosol washout/transfer efficiency. As reported previously (DOI: 10.1021/acs.analchem.6b02052), blur can be expressed as a convolution of the input image (representing the 2D elemental distribution) with point (PSF) and line (LSF) spread functions associated with ablation crater profiles and ICP-MS profiles of single pulses, respectively. Based on empirically derived PSFs and LSFs, and using a numerical calculation approach, the continuous-scanning LA-ICP-MS output of an angular-sensitive radial resolution target (Siemens star) was simulated to visualize the angular resolution dependency associated with ablation cell characteristics

Submicrometer imaging by laser ablation-inductively coupled plasma mass spectrometry via signal and image deconvolution approaches

In this work, pre- and postacquisition procedures for enhancing the lateral resolution of laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) in two- and three-dimensional (2D, 3D) nuclide distribution mapping beyond the laser beam waist are described. 2D images were constructed by projecting a rectangular grid of discrete LA positions, arranged at interspacings smaller than the dimensions of the laser beam waist, onto the sample surface, thus oversampling the region of interest and producing a 2D image convolved in the spatial domain. The pulse response peaks of a low-dispersion LA cell were isolated via signal deconvolution of the transient mass analyzer response. A 3D stack of 2D images was deconvolved by an iterative Richardson-Lucy algorithm with Total Variance regularization) enabling submicrometer image fidelity, demonstrated in the analysis of trace level features in corroded glass. A point spread function (PSF) could be derived from topography maps of single pulse craters from atomic force microscopy. This experimental PSF allows the approach to take into account the laser beam shape, beam aberrations, and the laser-solid interaction, which in turn enhances the spatial resolution of the reconstructed volume

Species kinetics and heterogeneous reactivity of dissolved Cu in natural freshwaters

Using high specific activity 64Cu2+ as radiotracer, the distribution kinetics among Cu species were established in natural organic-rich freshwaters under steady-state conditions, i.e., with minimal disturbance of existing equilibria. Study sites with contrasting suspended particulate matter (SPM) characteristics were investigated. Our analytical protocol allowed the differentiation between the following Cu species: SPM associated Cu, dissolved reactive (free and labile) Cu, and organically complexed Cu. The data obtained were successfully evaluated by compartmental analysis, which showed the importance of organically complexed Cu in freshwaters, and the dominant role of the interactions between organically complexed Cu and SPM in a SPM-rich water. The kinetic 64Cu measurements indicated that the attainment of equilibrium between dissolved reactive and organically complexed Cu took ca. <1-2 h, and 4-15 h for the interaction between dissolved organically complexed and SPM associated Cu. The kinetic study was augmented by voltammetric measurements of the dissolved (stable) Cu equilibrium speciation conditions in the natural waters. These measurements showed that the waters contained very low cupric ion concentrations (10-12-10-15 M), with more than 99.9% of the dissolved Cu complexed by strong organic ligands (conditional stability constants: 1013.4-1015.4)

Laser ablation-ICP-MS depth profiling to study ancient glass surface degradation

In general the analysis of archeological glass represents a challenge for a wide variety of objects because of the presence of physical and/or chemical damage on the surface of the artifact, also known as weathering or corrosion. To retrieve accurate bulk elemental information by laser ablationinductively coupled plasma-mass spectrometry (ICP-MS), the original, pristine glass needs to be Breached^, thereby penetrating the alteration layer which is often more than 10 μm thick. To study this alteration layer the laser was operated in the drilling mode, either with a low (1 Hz) or a high (10 Hz) pulse repetition rate for a period of 50 s yielding detailed spatial information for ca. 20 elements over a shallow depth (ca. 5 μm) or less-detailed spatial information for 50–60 elements over a greater depth (ca. 50 μm). Quantitative elemental depth profiles (in wt%) were obtained with the so-called sum normalization calibration protocol, based on summation of the elements as their oxides to 100 wt%.We were able to associate the increase of SiO2 (in wt%) in the alteration layer to the volumetric mass density change in the glass as a result of depletion of Na2O and K2O. Also the interaction of the number of laser shots with the alteration layer is shown experimentally via depth measurements using profilometry. Chemical and physical changes in four ancient glass artifacts, directly and indirectly measureable by laser drilling, were studied as a function of internal and external factors such as age, composition, and exposure conditions