Revealing the composition of organic materials in polychrome works of art: the role of mass spectrometry-based techniques

The most recent advances in the identification and determination of organic constituents in paintings and other polychrome objects using mass spectrometry (MS)-based techniques are reviewed. The latest achievements in gas chromatography (GC)-MS and pyrolysis (Py-) GC-MS are mainly related to sample pretreatment protocols and to the employment of double-shot or laser desorption pyrolysis, respectively. MS techniques based on soft ionization methods such as matrix assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) are discussed. So far, MALDI and ESI MS have been mainly used in the characterization of proteinaceous materials, but further applications are definitely emerging, e.g., in the fields of lipids, resins, and organic colorants analysis. Chemical imaging by time-of-flight secondary ion mass spectrometry (TOF SIMS), formerly applied to the detection and localization of lipid binders and inorganic materials, has been recently extended to proteins. Finally, the potential of niche techniques such as direct temperature resolved mass spectrometry (DTMS) and direct analysis in real time (DART) MS are outlined.