Spectroscopic characterization of recently excavated archaeological potsherds from Tamilnadu, India with multi-analytical approach

Pre-colonial culture and technology through elemental and molecular analysis of ceramics with decorative paintings found at Tapera beach, Florianópolis, Brazil

The chemical analysis of archaeological ceramic artifacts can help archaeologists to characterize the technology used in the manufacturing process, and to elucidate aspects related to the way of life of past peoples. In this context, six ceramic fragments found at Tapera Beach in Florianópolis were analyzed. FTIR spectroscopy was used to identify carbonates and oxalic acid originating from the biodegradation process. In the pictorial regions of the ceramics, iron oxides, manganese and chromium were present, along with calcium carbonate, which were used as pigments. In addition, the absence of characteristic bands for kaolinite suggests low firing temperatures (up to 900 °C). EDS confirmed the elements of the molecules identified by FTIR and showed the presence of Al and Si in the primary structure and Fe in the secondary structure of the ceramics. In addition, there were traces of rare earth elements in samples A3 and A5, which may be related to the geochemistry at the site from which the raw material was excavated. The GC-MS results showed the presence of lipids and the profile of the fatty acids detected suggested that the source of the oils adsorbed in the ceramic structure is vegetable.

ATR-FTIR and XRD quantification of solid mixtures using the asymptotic constant ratio (ACR) methods. Application to geological samples of sodium and potassium feldspars

Two asymptotic constant ratio methods applied to the quantification of individual components of solid samples using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD) are described. The methods involve the measurement of the peak current/peak areas of selected signals (diffraction peaks in XRD and absorption bands in ATR-FTIR) relative to the signal of standard added in constant proportion to the sample and the sample enriched with the analyte following the usual standard additions methodology. The proposed method compensates the absorption effects appearing in XRD and the presence of overlapping absorption bands of interferents by means of an asymptotic representation thus avoiding the need of the knowledge of the absorption parameters of the matrix and analytes. The method was tested for mixtures of different metal oxides and sodium and potassium feldspars with satisfactory results.

Quantification of minerals from ATR-FTIR spectra with spectral interferences using the MRC method

A method for quantifying the individual components of mineral samples based on attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR) is described, extending the constant ratio (CR) method to analytes absorbing in a common range of wavenumbers. Absorbance values in the spectral region where the analytes absorb relative to the absorbance of an internal standard absorbing at a wavenumber where the analytes do not absorb, permits the quantification of N analytes using measurements at N fixed wavenumbers. The method was tested for mixtures of albite, orthoclase, kaolin and quartz.