In situ identification of organic components of ink used in books from the 1900s by atmospheric pressure matrix assisted laser desorption ionization mass spectrometry

This paper describes the use of atmospheric pressure/matrix assisted laser desorption ionization-mass spectrometry (AP/MALDI-MS) as a spatially resolved analytical technique for the study of organic components of inks used to print coloured parts of ancient books. The possibility to operate at atmospheric pressure makes MALDI-MS a new in situ micro-destructive diagnostic tool suitable for analysing samples in air, simplifying the investigation of the organic components of artistic and archaeological objects. In this work, several organic dyes and pigments were identified in situ by analysing different coloured areas of books printed in the years 1911 and 1920. The detected colouring materials, which were available since the 1890s, were often identified as a mixture, confirming the typical procedures used in the lithographic printing processes. The matrix deposition and the laser desorption process did not cause visible alteration of the sample surface.