RAMAN TECHNIQUES APPLIED TO ANCIENT COSMETIC AND PHARMACEUTICAL PREPARATIONS

Complementary spectroscopic techniques, such as FT-IR and Micro-Raman spectroscopies are valuable means for maximizing the amount of information provided by complex matrices like the remains in archaeological containers. The difficulty in analyzing archaeological samples is due to their composition which generally involves a mixture of different inorganic and organic materials, some times degraded by the environmental conditions. We report the results of the vibrational spectroscopy techniques, such as Raman microscopy (laser 632 nm), FT-Raman spectroscopy (laser 1064 nm) and FT-IR/ATR with a golden gate accessory, of a first approach to the analysis of the ancient samples. The analytical results showed the importance of micro-Raman Spectroscopy in discriminating between inorganic and organic materials, thereby underlining the complexity of pharmaceutical and cosmetic matrices.Raman microscopy is the most suitable technique in order to identify minor inorganic components and contaminants at the micrometric scale inside these complex matrices. On the basis of the FT-IR and micro-Raman spectra, it was possible to identify some specific old cosmetic materials and some binders used in cosmetic preparations. In particular, Raman microscopy was able to identify the presence of constituents at the trace levels or compounds having vibrations at low wavenumbers within the sample examined, that it is not possible with normal FT-IR technique. This technique can easily identify compounds like lead oxide, red lead, cinnabar, rare minerals, (etc.) that could give interesting information about the original composition of the formulate and the provenance of the raw materials.Concerning the organic materials, their possibility of identification is very different from that of inorganic ones. Some compounds were rapidly degraded, some others persisted till to present day, often unchanged (e.g. wax). Historical samples are subjected to ageing and degradation process that make difficult to recognize the raw material originally present. For understanding the possible changes undergone by materials during ageing, a specific database of spectra must be available.In the project PRIN 2007 “Colours and balms in antiquity” some thirty raw materials were chosen among oils (e.g. olive, almond, and palm oil), gums (e.g. gumarabic), animal fats and waxes, commonly employed in the ancient preparations. The raw materials and the reference formulations prepared in the laboratory, were artificially aged. The reference Raman spectra have supplied an interesting database.The use of Surface-Enhanced Raman Spectroscopy (SERS) enabled to increase Raman signal and to decrease the background fluorescence for some samples. This techniques exhibits new perspectives for the study of organic and inorganic compounds in the field of cultural heritage.