Optimization of LA-ICP-MS. mapping of glass with decorative, coloured features – application to multi-elemental analysis of a polychrome glass vessel fragment from the Iron Age

2D elemental mapping of glass surfaces by LA-ICP-MS is an interesting technique to elucidate past technologies, establish provenance or understand deterioration processes of ancient, polychrome glass by visualization of the elemental distribution of the glass surface. However, selection of the appropriate LA-ICP-MS conditions for generation of high-quality elemental maps with the highest spatial resolution, lowest signal-to-noise ratio and shortest analysis time is normally a trial-and-error process. In this chapter a computational-experimental strategy is described to optimize the LA-ICP-MS conditions for 2D elemental mapping of polychrome glass by finding the best balance between fluence, beam diameter, repetition rate, scanning speed, gas flow rate and acquisition time. To aid in the initial selection of the optimal LA-ICP-MS conditions for spatial resolution and analysis time, a digital image of the glass was subjected to virtual 2D mapping, using existing software which simulates the actual LA-ICP-MS mapping process. To verify whether these initial conditions would result in an acceptable signal-to-noise ratio during the actual LA-ICP-MS mapping process, they were used to experimentally determine the detection limits for each element via a simple line scan on a “blank” glass, and consequently predict the noise floor in the maps. This strategy was successfully validated (using a modern murrina) and applied to a polychrome glass from the Iron Age yielding more insight into its elemental composition and the mineral sources involved.