Identification of inorganic pigments used in porcelain cards based on fusing Raman and X-ray fluorescence (XRF) data.

Raman spectroscopy and X-ray fluorescence (XRF) spectroscopy are often used as complementary techniques that are well suited for the analysis of art objects because both techniques are fast, sensitive, and noninvasive and measurements can take place in situ. In most of these studies, both techniques are used separately, in the sense that the spectra are evaluated independently and single conclusions are obtained, considering both results. This paper presents a data fusion procedure for Raman and XRF data for the characterization of pigments used in porcelain cards. For the classification of the analyzed points of the porcelain cards principal component analysis (PCA) was used. A first attempt was made to develop a new procedure for the identification of the pigments using a database containing the fused Raman-XRF data of 24 reference pigments. The results show that the classification based on the fused Raman-XRF data is significantly better than the classifications based on the Raman data or the XRF data separately.

In situ investigations of vault paintings in the Antwerp cathedral.

X-ray fluorescence spectroscopy (XRF) and Raman spectroscopy have been used to examine 15th century mediaeval and 16th century renaissance vault paintings in the Our Lady's Cathedral (Antwerp, Belgium) in view of their restoration. The use of mobile instruments made it possible to work totally non-destructively. This complementary approach yields information on the elemental (XRF) and on the molecular composition (Raman) of the pigments. For the 15th century vault painting the pigments lead-tin yellow (Pb(2)SnO(4)), lead white (2PbCO(3)xPb(OH)(2)), vermilion (HgS), massicot (PbO) and azurite (2CuCO(3).Cu(OH)(2)) could be identified. The pigments used for the 16th century vault painting could be identified as red lead (Pb(3)O(4)), hematite (Fe(2)O(3)), lead white (2PbCO(3)xPb(OH)(2)) and azurite (2CuCO(3)xCu(OH)(2)). For both paintings the presence of the strong Raman scatterer calcite (CaCO(3)) resulted in a difficult identification of the pigments by Raman spectroscopy. The presence of gypsum (CaSO(4)x2H(2)O) on the mediaeval vault painting probably indicates that degradation took place.

Detection of counterfeit Viagra with Raman spectroscopy.

During the last few years, counterfeiters have become increasingly sophisticated by falsifying drugs and making them look identical to genuine tablets. In this paper, Raman spectroscopy is proposed as a fast and reliable method for the detection of counterfeit Viagra tablets. This technique can easily differentiate genuine from counterfeit tablets without the need of sample preparation. In total 18 tablets were analysed which all contained the active ingredient sildenafil, but different excipients were used, as could be observed in the Raman spectra between 1150 and 700 cm(-1). So, the spectra could be divided into genuine or counterfeit. Additionally, principal component analysis (PCA), combined with hierarchical cluster analysis (HCA), was used to establish an automated approach for the discrimination of counterfeit from genuine Viagra tablets. Raman spectroscopy, combined with principal components analysis, could be used in the future by customs or in the field to identify counterfeit tablets on the spot without involvement of trained chemists.