Pyrolysis gas chromatography mass spectrometry of two green phthalocyanine pigments and their identification in paint systems

Copper phthalocyanine pigments are commonly used in modern paints, printing inks, plastics, leather, and synthetic fibres. Here, a systematic pyrolysis/gas chromatography-mass spectrometry study of two commonly used green copper phthalocyanine pigments (PG7 and PG36) was carried out. Pyrolysis temperatures ranging from 300 °C up to 800 °C were applied in order to study the pyrolysis products generated at each temperature. At temperatures above 700 °C very volatile products such as ClCN - for PG7 - and HBr, CHBr and BrCN - for PG36 - were relatively abundant, whereas at higher retention times a series of halogenated aromatic compounds could be identified. Py/GC-MS of green acrylic and oil paint systems containing PG7 and PG36 was also performed in order to verify the possibility to detect low amounts of copper phthalocyanine pigments in complex matrices. Although not all the pyrolysis products of the reference green copper phthalocyanine pigments could be detected, efficient identification of these pigments could be accomplished thanks to the presence of specific markers.