LA-ICP-MS analysis of African glass beads: Laboratory inter-comparison with an emphasis on the impact of corrosion on data interpretation

A comparison between the compositions determined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) from two different laboratories on 52 ancient beads recovered in Africa was undertaken. Single point and raster samplings by the laser ablation systems were used. Although similar results were obtained using the two approaches on most of the beads, raster sampling was found more sensitive to corrosion than single point sampling. The impact of corrosion on the results and on their interpretation is discussed. Depending on the types of glass, group attribution is variably affected.