ToF-SIMS Parallel Imaging MS/MS of Lead Soaps in Embedded Paint Cross Sections

In the field of cultural heritage, and more specifically in oil paintings, the ability to unambiguously identify and locate metal soaps is of great interest for a better understanding of painting degradation. Here, we demonstrate the use of a Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) instrument capable of tandem mass spectrometry imaging for the unambiguous identification and localization of lead soaps in cross sections of samples of old oil paintings at high spatial resolution. It is shown that the specific fragmentation pattern of lead soaps is dictated by the loss of the lead ion and that fragmentation occurs on the hydrocarbon chains of the fatty acids. This method offers new opportunities for a better understanding of the chemical changes in aging oil paint samples as well as investigation of organic pigments and binders.