Determination of metals in artistic pigments using the optimized GFAAS method and Raman spectroscopy

Abstract

Graphite furnace atomic absorption spectroscopy (GFAAS) was applied to identification of historical pigments. The method is adapted to determine different metals, usually found in pigments. Operating conditions were optimized, such as sample drying step, pyrolysis and atomization temperatures, modifiers, and volume of sample introduced into the atomizer, to reduce interferences due to a complex sample matrix. Using the optimized method pigments in samples from the painting Coronation of the Virgin from the Church of the Shroud of the Holy Virgin in Barič were identified. The samples were analyzed also by Raman microscopy to verify the identification achieved by GFAAS. Raman microscopy confirmed the assumptions made based on GFAAS results. Using the two techniques a variety of pigments have been identified, such as calcite, lead white, goethite, hematite, ultramarine, vermilion, minium, carbon black. Based on GFAAS results the presence of azurite was observed in the blue paint sample, although this finding was not confirmed by Raman microscopy.