Classification of late-antique glass : tandem-LIBS-LA-ICP-MS analysis and machine learning approach

Abstract

Elemental analysis of a material reveals its characteristic chemical fingerprint, aiding in identifying the provenance of the raw materials and providing insights into historical trading routes. In the field of Archaeological Science, Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is commonly used to analyze historical glass. This work aims to explore the advantages of incorporating Laser-Induced Breakdown Spectroscopy (LIBS) into the measurement setup, using Tandem-LIBS-LA-ICP-MS. The primary goal of this thesis is to develop a measurement methodology using the Tandem-LIBS-LA-ICP-MS configuration to generate high-quality data. This data will, in turn, be employed for the classification of the provided glass samples, utilizing a reference dataset that contains elemental analysis data derived from late-antique glasses as documented in existing literature.Overall 46 late-antique glass samples, excavated at Hemmaberg, Austria, were analyzed and quantified using Tandem-LIBS-LA-ICP-MS and the reference materials NIST® SRM® 610 and NIST® SRM® 612. Solid measurements were validated against acid-digested samples, measured using conventional liquid ICP-OES and -MS. Moreover, a OneClass Support Vector Machine (OCSVM) was employed to determine novel glass types within the analyzed samples. Also, a k-nearest neighbor (k-NN)-model was trained to determine the provenance and assign the samples to glass types documented in the literature.Solid measurements in general are minimal-invasive and sample preparation is less laborious. When it comes to quantification, the sum normalization method improved the results for two key elements when employing LIBS. This, in turn, enables the liberation of acquisition time in LA-ICP-MS, allowing for more precise measurements of other elements. Novelties could be detected and successful classification using k-NN was achieved using the samples’ base compositions, assessable through LIBS data exclusively. The use of Recycling Markers, measured via LA-ICP-MS, allowed for the identification of recycled glass.In the future, through the selection of more suitable reference materials and refining trace marker identification for sensitive LIBS measurements, it becomes feasible to eliminate the necessity of LA-ICP-MS within in the measurement setup. Such advancements could lead to LIBS-only measurements, potentially enabling handheld applications, greatly benefiting archaeologists in the field for rapid and on-site glass analysis.