Contents lists available at ScienceDirect Spectrochimica Acta Part B journal homepage: www.elsevier.com/locate/sab Analytical note Graph clustering and portable X-Ray Fluorescence: An application for in situ, fast and preliminary classifcation of transport amphoras E. Odelli a,b , V. Palleschi c , S. Legnaioli c , F. Cantini a , S. Raneri c, ⁎ a University of Pisa, Department of Civilization and Forms of Knowledge, Via dei Mille 19, 56126 Pisa, Italy b Department of Archaeology, Ghent University, Sint‑Pietersnieuwstraat 35, 9000 Ghent, Belgium c Applied and Laser Spectroscopy Laboratory, Institute of Chemistry of Organometallic Compounds, Research Area of National Research Council, Via G. Moruzzi, 1 – 56124 Pisa, Italy ARTICLE INFO Keywords: Potteries Portable ED-XRF Graph Clustering Provenance Non-destructive analysis ABSTRACT In the last decade, numerous papers have been delivered on the potential of portable X-Ray Fluorescence (XRF) in archaeological ceramics. Additionally, new chemometric methods have been proposed to manage chemical dataset and facilitate the use of geochemical discrimination for provenance classifcation of ancient ceramics. In this contribute, the potential of portable Energy Dispersive X-Ray Fluorescence (ED-XRF) analysis and chemical data processing by Graph Clustering is evaluated for provenance classifcation of archaeological potteries, dis- cussing possible merits and limits of the employed routine. A ceramic assemblage represented by seventy-three transport amphorae classifed by typological analysis have been used as testing materials; spectra have been collected on samples simulating in situ analysis conditions (e.g. on fresh cut surfaces without any preparation) and Graph Clustering method has been applied in chemical data processing; comparison with classical Cluster Analysis (CA) and Principal Component Analysis (PCA) is also evaluated. The obtained results favor the use of Graph Clustering for a preliminary classifcation of ceramics, which can be chemically analyzed in easy, fast and non-destructive way. With a 75.35% of correct attribution, the study shows the suitability of portable ED-XRF in rapid screening of a large number of ceramic samples usually recovered in the framework of archaeological excavation. Misclassifcations have been mostly verifed for samples exhibiting a coarse-grained clay paste, suggesting that the method is particularly suitable for fne-grained ceramic materials. 1. Introduction Potteries represent among the most numerous records in archae- ological excavation; archaeologists use potteries to create statistic compilation, periodization and typologies based on the similarities and diferences between types, styles or features that are relatively con- tinuous in time and/or geographic areas. Typological analysis usually support interpretation regarding trade routes and exchanges of goods among sites; however, certain provenance attribution often requires the support of compositional and geochemical analysis. The technological advancements and the development of afordable portable analytical methods has made possible the characterization of large number of artifacts quickly, easily and in non-destructive and non-invasive way [1–6], meeting the requirements of the archeologists to obtain the maximum amount of information from minute samples or directly in situ from intact objects. In this perspective, the use of portable X-Ray Fluorescence analysis for pottery analysis has drawn a great attention in the last decades; numerous papers have been in fact published trying to understand the afordability of portable chemical methods in ceramic classifcation and provenance investigation [7,8]. The literature in the feld seems to be split in two main factions, including researchers considering the ap- plication of portable ED-XRF in ceramic and sediment studies as a challenge, although recognizing its limits and drawbacks [9–16], and others which warns against the limits of a technique that cannot sub- stitute the classical chemical investigations [17]. Actually, limitations due to detection limits in light elements, density of analyzed materials, surfaces vs. bulk composition, heterogeneity of ceramic materials, variability in measured intensity and matrix efects have to be taken in great consideration in ED-XRF analysis of potteries [18]. The replace- ment of chemical analytical methods with portable XRF is not possible; however, the application of carefully tailored measurement and pro- cessing protocols might provide good statistical results, returning classifcations similar to the ones obtained by laboratory methods such https://doi.org/10.1016/j.sab.2020.105966 Received 5 May 2020; Received in revised form 20 August 2020; Accepted 22 August 2020 ⁎ Corresponding author. E-mail address: simona.raneri@pi.iccom.cnr.it (S. Raneri). Spectrochimica Acta Part B 172 (2020) 105966 Available online 25 August 2020 0584-8547/ © 2020 Elsevier B.V. All rights reserved. T