Matthieu Ménager

Analysis of diterpenic compounds by GC-MS/MS: contribution to the identification of main conifer resins

AbstractThe three principal types of molecules composing diterpenic resins are the abietanes, pimaranes and labdanes. The study of their fragmentation was performed by gas chromatography coupled to an ion trap mass spectrometer, on standards and resins used in paint varnishes: colophony and sandarac. We found that the general fragmentation pattern was mostly governed by the location of the double bonds on the different cycles and the presence of functional groups, and not by the nature of the C13 group in the case of abietanes and pimaranes. As for the labdanes, the loss of their alkyl chain is very specific. This study develops an analytical strategy using tandem mass spectrometry (MS/MS) experiments to validate the proposed mechanisms of fragmentation and to find the ions of interest for the identification of diterpenic molecules. Graphical AbstractAnalysis of diterpenic compounds by GC-MS/MS

Spectral Behavior of White Pigment Mixtures Using Reflectance, Ultraviolet—Fluorescence Spectroscopy, and Multispectral Imaging

Reflectance spectroscopy, ultraviolet (UV)—fluorescence spectroscopy, and multispectral imaging have been widely employed for pigment identification on paintings. From ancient times to the present, lead white, zinc white, and titanium white have been the most important white pigments used for paintings and they are used as pigment markers for dating a work of art. The spectral behavior of these pigments is reported in several scientific papers and websites, but those of their mixtures are quite unknown. We present a combined nondestructive approach for identifying mixtures of lead white, zinc white, and titanium white as powder and dispersed in two different binder media (egg yolk and linseed oil) by using reflectance spectroscopy, spectrofluorimetry, multispectral reflectance and UV-fluorescence imaging. We propose a novel approach for mapping the presence of white pigments in paintings by false color images obtained from multispectral reflectance and UV-fluorescence images. We found that the presence of lead white mixed with either zinc white or titanium white is highly detectable. Zinc white mixed with lead white or titanium white can be identified due to its UV-fluorescence emission, whereas titanium white in association with lead white or zinc white is distinguishable by its reflectance spectral features. In most cases, the UV-fluorescence analyses also permit the recognition of the binder media in which the pigments are dispersed.