- Characterisation of metal carboxylates by Raman and infrared spectroscopy in works of art
-
This work introduces the complementary use of μ-Raman and μ-Fourier transform infrared (IR) spectroscopy for the detection of specific carbon chains and cations for the identification of metal carboxylates within oil paint microsamples. Metal carboxylates (metal soaps) form naturally when free fatty acids react with metal cations and may also be found as additives or degradation products. Twenty-two metal carboxylates were synthesised, and their spectra assembled in a reference database. Metal salts of cations commonly present in oil paintings were used, including lead, zinc, calcium, cadmium, copper and manganese. The fatty acids selected were the saturated acids palmitic (C1 6:0) and stearic (C18:0) and the polyunsaturated oleic acid (C1 8:1). Azelaic acid (C9 diacid), a product resulting from autoxidation of polyunsaturated acids, was also included. Metal carboxylates were characterised by Raman and IR spectroscopy, and their structures were confirmed by X-ray diffraction. Raman and IR spectroscopy proved to be complementary techniques for a full identification of the metal carboxylates in complex aged paint. Raman enables the differentiation of the carbon chain length in the C-C stretching region (1120-1040 cm-1), and IR distinguishes the metal cation in the COO- stretching absorption region (1650-1380cm-1). Principal component analysis was applied to the spectra in order to facilitate a fast and accurate method to discriminate between the different metal carboxylates and to aide in their identification. Finally, spectra from case studies were successfully projected in the principal component analysis models built, enabling a higher confidence level for the identification of copper palmitate and copper azelate in two 19th-century Portuguese oil paintings.
- Otero, Vanessa,Sanches, Diogo,Montagner, Cristina,Vilarigues, Mrcia,Carlyle, Leslie,Lopes, Joo A.,Melo, Maria J.
-
p. 1197 - 1206
(2015/02/19)
-
- A GLYCEROL DERIVED MATERIAL
-
A method of producing a solid glycerol derived material includes the steps of combining glycerol with a metal oxide, the glycerol having a water content of between about 5 and 50%, and the rate of combination of the glycerol and the metal oxide and the amount of the metal oxide being selected so that at least part of the water present in the glycerol reacts with the metal oxide in an exothermic reaction and at least part is driven off by heat produced in the exothermic reaction to produce the solid glycerol derived material.
- -
-
Page/Page column 54 - 55
(2010/04/03)
-