Multi-technique characterisation of commercial alizarin-based lakes

Lucilla Pronti; Jean-Baptiste Mazzitelli; Maria Paola Bracciale; Lorenzo Massini Rosati; Cathy Vieillescazes; Maria Laura Santarelli; Anna Candida Felici

doi:10.1016/j.saa.2018.04.008

Multi-technique characterisation of commercial alizarin-based lakes

Spectrochim Acta A Mol Biomol Spectrosc. 2018 Jul 5:200:10-19. doi: 10.1016/j.saa.2018.04.008. Epub 2018 Apr 7.

Authors

Lucilla Pronti¹, Jean-Baptiste Mazzitelli², Maria Paola Bracciale³, Lorenzo Massini Rosati⁴, Cathy Vieillescazes², Maria Laura Santarelli³, Anna Candida Felici⁴

Affiliations

¹ Department of Basic and Applied Sciences for Engineering, LANDA-Laboratory of Archaeometry and Non Destructive Analysis, University of Rome Sapienza, via A. Scarpa 16, 00161 Rome, Italy. Electronic address: lucilla.pronti@uniroma1.it.
² Restoration Engineering of Natural and Cultural Heritage, IMBE Laboratory, Avignon University/CNRS/IRD/AMU, UFR-ip STS, Campus Jean-Henri Fabre, 301 rue Baruch de Spinoza BP 21239, 84916 Avignon cedex 9, France.
³ Department of Chemical Engineering Materials and Environment and CISTeC- Research Center in Science and Technology for the Preservation of Historical-architectural Heritage, University of Rome Sapienza, via Eudossiana 18, 00184 Rome, Italy.
⁴ Department of Basic and Applied Sciences for Engineering, LANDA-Laboratory of Archaeometry and Non Destructive Analysis, University of Rome Sapienza, via A. Scarpa 16, 00161 Rome, Italy.

PMID: 29660677
DOI: 10.1016/j.saa.2018.04.008

Abstract

The characterization of ancient and modern alizarin-based lakes is a largely studied topic in the literature. Analytical data on contemporary alizarin-based lakes, however, are still poor, though of primary importance, since these lakes might be indeed present in contemporary and fake paintings as well as in retouchings. In this work we systematically investigate the chemical composition and the optical features of fifteen alizarin-based lakes, by a multi-analytical technique approach combining spectroscopic methods (i.e. Energy Dispersive X-ray Fluorescence Spectroscopy, EDXRF; Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy, ATR-FTIR; X-ray Powder Diffraction, XRD; UV induced fluorescence and reflectance spectroscopies) and chromatography (i.e. High-performance Liquid Chromatography coupled with a Photodiode Array Detector, HPLC-PDA). Most of the samples contain typical compounds from the natural roots of madder, as occurring in ancient and modern lakes, but in two samples (23600-Kremer-Pigmente and alizarin crimson-Zecchi) any anthraquinonic structures were identified, thus leading to hypothesize the presence of synthetic dyes. The detection of lucidin primeveroside and ruberythrique acid in some lakes suggest the use of Rubia tinctorum. One sample (23610-Kremer-Pigmente) presents alizarin as the sole compound, thereby revealing to be a synthetic dye. Moreover, gibbsite, alunite and kaolinite were found to be used as substrates and/or mordants. Visible absorption spectra of the anthraquinonic lakes show two main absorption bands at about 494-511nm and 537-564nm, along with a shoulder at about 473-479nm in presence of high amounts of purpurin. Finally, from the results obtained by UV induced fluorescence spectroscopy it is possible to figure out that, although it is commonly assumed that the madder lake presents an orange-pink fluorescence, the inorganic compounds, added to the recipe, could induce a quenching phenomenon or an inhibition of the fluorescence, as occurring in some commercial alizarin-based lakes.

Keywords: ATR-FTIR; Alizarin-based lakes; HPLC-PDA; Reflectance spectroscopy; UV induced fluorescence spectroscopy; XRD.