Applications of laser desorption mass spectrometry for the study of synthetic organic pigments in works of art

This paper describes the application of laser desorption mass spectrometry (LDMS) to the identification of synthetic organic pigments in microscopic samples from works of art. This work demonstrates the value of LDMS as a complementary analytical tool for use in the conservation laboratory alongside techniques such as Fourier transform infrared (FTIR) spectroscopy and energy dispersive spectroscopy (EDS). In many cases LDMS, used in both positive and negative ion modes, provides sensitive and specific identification of pigments based on exact mass, fragment ions, and isotopic patterns. The analyses are rapid, require minimal sample preparation, and are often free from significant interferences from background or additional components such as paint binding media. High-confidence identifications are achieved even for samples containing mixtures of colorants, including inorganic pigments in some cases. Examples are presented in which LDMS provided data that was valuable in addressing questions regarding materials used in paintings attributed to Jackson Pollock and in the investigation of the materials and techniques of the self-taught American artist James Castle.