Development of a method based on high‐performance liquid chromatography coupled with diode array, fluorescence, and mass spectrometric detectors for the analysis of eosin at trace levels

Abstract

Eosin (Acid Red 87, C.I. 45380) is one of the most brilliant and challenging early synthetic dyes. In this study, an analytical approach based on high‐performance liquid chromatography coupled with diode array and fluorescence detector and high resolution mass spectrometry was developed for testing different analytical columns and acids in the mobile phase. The ultra‐sensitive approach, based on a chromatographic separation on a solid core and a porous shell Poroshell 120 EC‐C18, allowed us to detect and characterize eosin and its synthesis by‐products, such as the debrominated and methyl ester forms of eosin, in trace levels (the limit of detection for eosin is 0.13 ppb). The resulting miscellaneous composition of the eosin standard highlights the importance to determine the exact composition of the starting material to deal with, in order to avoid misinterpretations in aged or degraded samples. Finally, the successful identification of eosin in few grains (approximatively 20 × 40 μm wide) of a faded Van Gogh's painting proved the strengths of our approach.

High-Resolution Mass Spectrometry and Nontraditional Mass Defect Analysis of Brominated Historical Pigments

“…A series of recent publications focused on the detection of geranium lakes by mass spectrometry have contributed very significantly to this research topic. − Nevertheless, the side products formed during the synthesis of geranium lakes, as well as their degradation mechanisms in oil paintings, are still unclear. In addition, it has been observed that the metal used to complex the eosin could affect the lightfastness due to the molecular structure of the lake. , However, up to now, no mass spectrometric analysis has been performed to reach a deeper understanding of the possible degradation process of the different metallic complexes.…”

Chemical Mapping of the Degradation of Geranium Lake in Paint Cross Sections by MALDI-MSI

“…These signals were assigned by comparison with data reported previously, , analyzing their isotopic patterns and distributions, and evaluating the possible additions to the most intense and monoisotopic ions based on mass differences. As GL was widely used by Van Gogh, its degradation pathway has been extensively investigated in solution and mock-up samples. ,,− These studies have revealed that an intermediate mechanism can be associated with the debromination process of the eosin molecule before leading to the breakdown of the xanthene moiety that causes total discoloration. ,, The ability to perform distribution analysis of the intact eosin monomer and its known degradation products on paint cross sections was evaluated next. 10 μm spatial resolution ion images of these characteristic ions in samples GL100 and GL50 are presented in Figure B,C.…”

Investigating the in‐solution photodegradation pathway of Diamond Green G by chromatography and mass spectrometry

“…The irradiation in‐solution of DG was carried out both in water and in DMSO to evaluate possible differences in the degradation process. In particular, because an extraction procedure based on the use of DMSO revealed its potential both in terms of its efficiency and speed for the analysis of synthetic dyes and pigments, 35‐37 the photochemical behaviour of DG in this solvent was of great interest. The UHPLC‐DAD chromatograms (corresponding to absorption at 600 and 254 nm) of the aliquots sampled from both solutions are presented in Figures 1A,B and 2A,B.…”