Macro-ATR-FT-IR spectroscopic imaging analysis of paint cross-sections

Macro-attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopic imaging is presented as non-destructive analytical methodology with respect to the sample for the study of paint surfaces. This paper illustrates new opportunities offered by a conventional diamond ATR accessory coupled with a focal plane array detector to obtain chemical images of multi-layered paint cross-sections. The use of a large internal reflection element permits to increase the field of view of the imaging area up to 700 μm × 500 μm and to obtain FT-IR images of the complete stratigraphy of the sample. This approach represents a versatile analytical tool to determine the composition of the inorganic and organic painting materials and to obtain information on their distribution within the different layers. In the optical arrangement used, a spatial resolution of approximately 15 μm is achieved without the use of infrared microscope. This study demonstrates the possibilities offered by macro-ATR-FT-IR imaging for a simple identification of the different compounds present in paint cross-sections before performing further molecular and elemental analyses which may be time consuming or require particular sample preparation.