Multi-element LA-ICP-MS analysis of the clay fraction of archaeological pottery in provenance studies: a methodological investigation† Marieke Vannoorenberghe, a Thibaut Van Acker, a Joke Belza, a Dimitri Teetaert, a Philippe Cromb ´ e b and Frank Vanhaecke * a Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an increasingly popular direct solid sampling micro-analytical technique for multi-element analysis in provenance studies of archaeological pottery. However, the development and use of a reliable quantification strategy for the analysis of pottery clay via ns-LA-ICP-MS is not self-evident due to the lack of commercially available matrix-matched clay reference materials covering a wide range of characterized element concentrations. In this work, the capabilities and limitations of various calibration approaches were evaluated, based on the analysis of NIST SRM 679 Brick Clay as a model sample. Calibration relied on the use of either (i) 5 glass reference materials or (ii) the matrix-matched reference material New Ohio Red Clay (NORC) as external calibration standard(s). Four calibration strategies were compared and it was shown that (a) external calibration without internal standard correction is not suitable when using glass reference materials for calibration, but can be used in the case of calibration against a clay reference material, (b) different sum normalization approaches produce results that are very similar to each other and (c) glass reference materials used as standards in an external calibration approach with internal standard correction or a sum normalization method can provide accurate results for a wide range of major, minor and trace elements. Finally, the utility of an appropriate sum normalization calibration approach was illustrated by analysis of 10 sediments relevant to provenance studies of Final Mesolithic and Early Neolithic pottery in the Scheldt valley and their successful discrimination employing linear discriminant analysis (LDA) based on 44 element concentrations. The use of polished sediment thin sections in combination with transmitted light microscopy enabled the clay fraction of the sediments only to be meticulously sampled. A dedicated outlier rejection protocol was applied to minimize the contribution of non-visible constituents. Introduction Ceramic ware is one of the most commonly found archaeolog- ical objects all over the world due to the fact that red clay barely deteriorates over time. Therefore, these artefacts poten- tially contain a lot of information on practices of people over a long period in history. For a long time, archaeologists have studied ceramics purely based on macroscopic observations. 1 More recently, there is a shi towards the use of physico- chemical techniques to answer questions like when, where, how and for which purpose the ceramics were manufactured. 2 Commonly used approaches include mineralogical analysis via X-ray powder diffraction analysis (XRPD), petrographic analysis and chemical analysis, e.g., using instrumental neutron activa- tion analysis (INAA), inductively coupled plasma-optical emis- sion spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray uorescence spectroscopy (XRF). Chemical analysis has the potential to discriminate between pottery samples manufactured from sediments of different origin, even when their mineralogy is quite similar. However, a combination of techniques addressing the chem- ical, petrological, mineralogical and textural features of pottery is usually advised to obtain all relevant information. 3 The composition of ancient pottery is oen highly heterogeneous, containing both natural inclusions and varying amounts of temper, i.e. non-plastic material added to the clay paste by the potter. A wide range of temper materials has been reported in archaeological context (e.g., sand, shell, pulverized minerals and plant materials) and the addition is oen linked to cultural a Atomic and Mass Spectrometry – A&MS Research Unit, Department of Chemistry, Ghent University, Campus Sterre, Krijgslaan 281 – S12, 9000 Ghent, Belgium. E-mail: frank.vanhaecke@ugent.be b Prehistory of Europe Research Unit, Department of Archaeology, Ghent University, Campus UFO, Sint-Pietersnieuwstraat 35, 9000 Ghent, Belgium † Electronic supplementary information (ESI) available: Information on the sediment samples analysed (Table S1), LOD values (Table S2), experimental and reference concentrations and relative standard deviations (Tables S3–S6). See DOI: 10.1039/d0ja00286k Cite this: J. Anal. At. Spectrom. , 2020, 35, 2686 Received 13th June 2020 Accepted 10th September 2020 DOI: 10.1039/d0ja00286k rsc.li/jaas 2686 | J. Anal. At. Spectrom. , 2020, 35, 2686–2696 This journal is © The Royal Society of Chemistry 2020 JAAS PAPER Published on 11 September 2020. Downloaded by Ghent University Library on 8/3/2022 9:27:15 AM. View Article Online View Journal | View Issue