3D laser ablation-ICP-mass spectrometry mapping for the study of surface layer phenomena – a case study for weathered glass

Abstract

In this work, a multi-elemental 3D laser ablation-ICP-mass spectrometry mapping procedure for highresolution depth information retrieval to investigate surface layer phenomena is presented. The procedure is based on laser drilling on a virtual grid on the surface, followed by extraction of depth maps along the z-axis (for each element monitored). Using a burst of 50 laser pulses at 1 Hz on each point of the grid, a penetration rate of ca. 150 nm per pulse (in glass) was obtained and a lateral resolution in the order of the laser beam diameter. By ultrafast ICP-MS monitoring of individual ablation pulses (58 ms for a set of 19 elements) using a laser ablation cell with fast signal washout (less than 0.5 s for whole laser pulse), the corresponding peak areas could be consistently integrated, resulting in spatial elemental data associated with individual pulses. The usual laser drilling limitations such as pulse mixing and signal tailing are avoided with this approach. After manipulation of the spatial elemental datasets and quantification, stacks of 50 2D depth maps (for each element monitored) were produced which could be visualized as volume images or time-lapse movies. As a proof of concept, this approach was successfully used to investigate the degradation mechanisms of a medieval, weathered glass artifact by colocalization analysis of selected cross-sectional 2D elemental images in arbitrary planes of the volume images. It was shown that degradation must have started as a result of dealkalinization leading to depletion of alkalis/earth alkalis in glass surface layers and enrichment of network formers (Si and Al), and subsequent worsening by cracking and formation of corrosion pits and so-called spatiotemporal Liesegang rings indicative of radial leaching.

Archaeometric investigations of medieval stained glass panels from Grodziec in Poland

“…Thus Ca and K-ions are leached out of the glass, which is a typical result of glass deterioration caused by an ion exchange between H-ions in water deposited on the glass surface. Enrichment of SiO 2 at the surface is a result of increasing density of glass surface due to depletion of alkaline ions [26,27]. Nevertheless, Na 2 O enrichment at the surface (Fig.…”

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

“…For example, the effective lateral resolution when scanning a surface at 20 mm s À1 with a laser beam of 5 mm in diameter, ring at 20 Hz, could amount to 20-40 mm. This shortcoming can be compensated for by operating at low sampling rates, effectively separating the pulse responses within one or more sequences of pulses, 9 or by operating at high sampling rates and low scanning speeds, thereby mixing the dispersion of multiple overlapping signal peaks over a short scanning range. 10 Both options lead to a decreased sample throughput and thus, increased costs.…”

“…This factor is, however, of minimal importance due to the good correlation between crater depth and a limited (<20) number of pulses. 9 Residual variation within the integrated area may originate from laser uence instability (typically <1%), plasma shielding by inverse Bremsstrahlung and photoionization, changing transport properties (temporal variation in the particle size distribution), target zone lateral inhomogeneity on a micrometer scale, and instability and stochastic noise within the ICP-MS unit.…”

A moderate microsampling in Laser Ablation Inductively Coupled Plasma Mass Spectrometry analysis of cultural heritage objects: a review

“…Van Elteren with co-workers [180] applied a 3D LA-ICP-MS mapping procedure to the analysis of historic glass to study degradation mechanisms of glass weathering. Previous analytical protocols required cross-sectional fragments of glass for the analysis, which was omitted in this project.…”

“…Imaging techniques allow for clear mapping of a distribution of selected elements in forms of 2D [53,90,147,174] or 3D [180] models. Van Elteren with co-workers [180] applied a 3D LA-ICP-MS mapping procedure to the analysis of historic glass to study degradation mechanisms of glass weathering.…”