Contents lists available at ScienceDirect Microchemical Journal journal homepage: www.elsevier.com/locate/microc Gel substrates and ammonia-EDTA extraction solution: a new non- destructive combined approach for the identifcation of anthraquinone dyes from wool textiles G. Germinario a, ⁎ , A. Ciccola b , I. Serafni b , L. Ruggiero c , M. Sbroscia c , F. Vincenti b , C. Fasolato d , R. Curini b , M. Ioele a , P. Postorino e , A. Sodo c a Istituto Centrale per il Restauro (ICR), via di San Michele 25, 00153, Roma, Italy b Dipartimento di Chimica, Sapienza Università degli Studi di Roma, Piazzale Aldo Moro 5, 00185, Roma, Italy c Dipartimento di Scienze, Università degli Studi “Roma Tre”, via della Vasca Navale, 84, 00146, Roma, Italy d Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, via Alessandro Pascoli, 06123, Perugia, Italy e Dipartimento di Fisica, Sapienza Università degli studi di Roma, Piazzale Aldo Moro 5, 00185, Roma, Italy ARTICLEINFO Keywords: Anthraquinones Ammonia-edta solution Dyes extraction SERS Raman HPLC-HRMS SEM-EDS ABSTRACT The identifcation of dyes from ancient textiles represents a challenging issue requiring high profciency and versatility, that must be guided by the principles of non-destructiveness. The complexity of the dye/textile system infuences both the choice of sampling and extraction procedures and the analytical methodology. For instance, in order to preserve both the fbre and the original chromophores on it, the extraction procedures commonly used for natural dyes have evolved in last few decades towards increasingly mild conditions. Along with this approach, the use of solid substrates for sampling has become prominent in several felds of Cultural Heritage diagnostics.With reference to these two aspects, the aim of this work is to combine gel substrates and a mild basic solution for the extraction of anthraquinone dyes (madder and cochineal) from wool textiles, in order to evaluate the versatility of the extraction procedure for diferent analytical techniques. Because of their wide use in the feld of Conservation, agar and nanorestore gel substrates soaked in an ammonia-EDTA solution were tested. The dye-extracting substrates were then analysed with Raman and SERS spectroscopy, whilst the fraction re-extracted from them was examined with HPLC-HRMS. Finally, scanning electron microscopy was used to monitor the integrity of the wool after the extraction treatment with the ammonia-EDTA solution.HPLC-HRMS resultsshowthatthebasicsolutioninbothgelsisefective forthedyeextraction,andnoalterationofwool fbres was evidenced by SEM-EDS. The Raman spectra give no information about the dyes, but only substrate signals are obtained. Conversely, SERS spectroscopy makes it possible to distinguish the two dyes, especially using the 633 nm laser on the agar substrate. 1. Introduction Until the introduction of synthetic dyes in nineteenth century, the main sources for the production of dyes (in order to obtain coloured yarnsfortapestriesortomakelakepigments)havebeenplants,rootsor insects. Considering the natural matrices employed across past cen- turies, it is undoubted that madder and cochineal dyes represent the most important class used for red dyeing [1–4]. The roots of the Rubia tinctorum specie contains alizarin, purpurin, xantopurpurin, pseudo- purpurin and munjistine anthraquinones; whilst [3,5,6]the Coccus cacti insects present the carminic acid as the main dye of a complex mixture because of its high content, together with proteins and quinine [5,7–10]. Indeed, it is worthy of notice that the strong colouring fea- tures are obviously not reducible to only these dye molecules, but natural dyes show a complex molecular pattern, composed by agly- cones and as glycosides [11,12] which are fxed on natural fbres with diferent metal ions (i.e. tin, iron or aluminium) as mordants [5–13]. As amply demonstrated in diferent papers focused on Cultural Heritage conservation, the identifcation of natural dyes is a very im- portant task to understand the dyeing procedure, to recognize the natural source employed and then, consequently, to hypothesize the geographical provenance and the ancient commercial trades, as well as to defne an optimal conservation and restoration protocol [7,12,14,15]. https://doi.org/10.1016/j.microc.2020.104780 Received 30 August 2019; Received in revised form 25 February 2020; Accepted 26 February 2020 ⁎ Corresponding author. Istituto Centrale per il Restauro (ICR), via di San Michele 25, 00153, Roma, Italy E-mail address: giulia.germinario@beniculturali.it (G. Germinario). Microchemical Journal 155 (2020) 104780 Available online 27 February 2020 0026-265X/ © 2020 Elsevier B.V. All rights reserved. T