XPS, ICP and DPASV analysis of medieval pottery — Statistical multivariate treatment of data

Medieval ceramic sherds have been studied by inductively coupled plasma (ICP) emission spectroscopy and X-ray photoelectron spectroscopy (XPS) in order to acquire knowledge about technological achievements in pottery production in Apulia during the Middle Ages. The XPS results allow to characterize the surface glazes, which are transparent owing to the presence of PbO or opaque-white in case of Sn addition. The study of coloured glossy surfaces, after an optimized chemical etching, has also shed light on the pigment nature of the painted decorations, whose red colour is to be attributed to the presence of Pb₃O₄ and not of Fe oxides. Quantitative determinations were performed by ICP measurements on samples of differently coloured glazes, clayey slips and ceramic bulks. Pb and Cu, present in one green glaze, were also determined by differential pulsed anodic stripping voltammetry (DPASV). The analytical results were treated by different statistical techniques of multivariate analysis.     

Determination of the acid dissociation constant of bromocresol green and cresol red in water/AOT/isooctane reverse micelles by multiple linear regression and extended principal component analysis

The pKa of 3',3",5',5"tetrabromo-m-cresolsulfonephtalein (Bromocresol Green) and o-cresolsulphonephtalein (Cresol Red) was spectrophotometrically measured in a water/AOT/isooctane microemulsion in the presence of a series of buffers carrying different charges at different water/surfactant ratios. Extended Principal Component Analysis was used for a precise determination of the apparent pKa and of the spectra of the acid and base forms of the dye. The apparent pKa of dyes in water-in-oil microemulsions depends on the charge of the acid and base forms of the buffers present in the water pool. Combination with multiple linear regression increases the precision. Results are discussed taking into account the profile of the electrostatic potential in the water pool and the possible partition of the indicator between the aqueous core and the surfactant. The pKa corrected for these effects are independent of w0 and are close to the value of the pKa in bulk water. On the basis of a tentative hypothesis it is possible to calculate the true pKa of the buffer in the pool.     

An archaeometric approach about the study of medieval glass from Siponto (Foggia, Italy)

Medieval glasses, including feet and rims of chalices, fragments of lamps and globular bottles, coming from the archaeological site of Siponto (Foggia, Italy), were analyzed by Inductively Coupled Plasma Emission Spectroscopy and Graphite Furnace Atomic Absorption Spectroscopy for investigating and defining glass production technology in Apulia (Italy) in the Middle Ages, because of the poor understanding currently achieved on either compositional and technological features of medieval glass items. The examined finds, whether colourless or coloured blue, yellow-green, yellow, pink and red, revealed a typical silica-soda-lime-composition. The chemical analysis and the statistical treatment of data allowed to trace former, flux, modifier and, where it is present, the element responsible for colour, clarifying production technology issues. It has been possible to identify, moreover, objects obtained by recycling of cullets or finished items.Finally, this work evaluates the effectiveness of the statistical multivariate treatment by Principal Component Analysis (PCA), Clustering Analysis (CA) and Factor Analysis (FA) on compositional data to obtain technological information in opposition to the conventional binary oxides diagram, which represent the most common, widely assessed, archaeometrical practice to obtain technological information from compositional data.     

An integrated spectroscopic approach to investigate pigments and engobes on pre‐Roman pottery

Painted Canosa ceramics were examined to identify the nature of the pigments employed and their manufacturing technology. A multi‐technique approach was used, comprising Raman microspectroscopy and laser ablation hyphenated to inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). The analysed samples were mainly produced for burial in tombs and were not intended for everyday use. They belong to the period between the end of the mid‐7th century and the first half of the 4th century BC, and were excavated from the Toppicelli archaeological district near the suburbs of Canosa (Puglia, Italy). Forty‐eight pottery fragments were available for this study. No handling of the samples was required for the Raman study, and it was possible to excise the pigmented layer in such a way that the lacunae were not distinguishable to the naked eye due to the micrometric size of the laser spot as far as LA‐ICP‐MS is concerned. Their combination turned out to be quite useful for the investigation of these archaeological materials: the chemical nature of the white, red, brown and black pigments employed in the pottery manufacture was investigated. Iron and manganese compounds were identified as the red and brown/black main colouring substances, respectively; on the other hand, whites and engobes (whitish slips) were based on kaolinite. This set of colouring substances is of importance, as it enabled the artisan to obtain in one oxidising firing cycle brown, black and red paints. Finally, the finding of manganese black in these Canosa potsherds confirms that Canosa was an important centre connecting the near East to central Italy and Europe since the pre‐Roman age. Copyright © 2010 John Wiley & Sons, Ltd.     

Lipase-Catalyzed Acylation and Deacylation Reactions of Pyridoxine,a Member of Vitamin-B6 Group

A series of acyloxy derivatives of pyridoxine ( 1 ) have been prepared by transesterification reactions of 1 and ethyl carboxylates, catalyzed by several lipases. Moreover, acetylated derivatives of 1 were selectively deacetylated by enzymatic catalysis in organic media.     

Investigations by various analytical techniques to the correct classification of archaeological finds and delineation of technological features: Late Roman lamps from Egnatia: From imports to local production

Late Roman oil lamps from the archaeological site of Egnatia (Fasano, Brindisi, Italy) were characterized from physical–chemical, mineralogical and morphological points of view. Atomic Spectroscopy, Scanning Electron Microscopy and X-Ray Diffraction analyses were carried out on ceramic body and coatings with the aim of identifying the provenance of lamps, in order to arrive at a correct archaeological classification of finds and to outline their technological features.The analytical results show that the finds differ in raw materials and in production technology. The statistical multivariate treatment of compositional data of ceramic bodies groups the objects into two macro clusters and, according to a study of their different petrographic features and by a comparison with coeval pottery whose provenance is already known, suggests one group to have been imported from North Africa and the other to have been locally produced. Moreover, chemical results and in-depth archaeological analyses allow us to split the imported lamps into two subgroups, hypothesizing the first group to originate from central Tunisia and the second from the north of the same country.The analytical characterisation of finds, by different complementary techniques, has allowed us to identify the raw materials and the technological solutions used by the ancient potters from Egnatia to produce lamps. The potters made lamps which had an external appearance very similar to that of African prototypes, but which were nevertheless different as they employed the locally available materials.     

Application of Multiple Linear Regression and Extended Principal-Component Analysis to Determination of the Acid Dissociation Constant of 7-Hydroxycoumarin in Water/AOT/Isooctane Reverse Micelles

The apparent pK(a) of dyes in water-in-oil microemulsions depends on the charge of the acid and base forms of the buffers present in the water pool. Extended principal-component analysis allows the precise determination of the apparent pK(a) and of the spectra of the acid and base forms of the dye. Combination with multiple linear regression increases the precision. The pK(a) of 7-hydroxycoumarin (umbelliferone) was spectrophotometrically measured in a water/AOT/isooctane microemulsion in the presence of a series of buffers carrying different charges at various different water/surfactant ratios. The spectra of the acid and base forms of the dye in the microemulsion are very similar to those in bulk water in the presence of Tris and ammonia. The presence of carbonate changes somewhat the spectrum of the acid form. Results are discussed taking into account the profile of the electrostatic potential drop in the water pool and the possible partition of umbelliferone between the aqueous core and the surfactant. The pK(a) values corrected for these effects are independent of w(0) and are close to the value of the pK(a) in bulk water. Copyright 2000 Academic Press.     

Laser-induced breakdown spectroscopy of archaeological findings with calibration-free inverse method: Comparison with classical laser-induced breakdown spectroscopy and conventional techniques

A modified version of the calibration-free (CF) method was applied to the analysis of a set of archaeological brooches made of various copper-based alloys and coming from the archaeological site of Egnatia (Apulia, Southern Italy). The developed methodology consists in determining the plasma temperature by reversing the set of equations employed in the usual CF algorithm, and it is thus referred to as “inverse method”. The plasma temperature is determined for one certified standard, by using its known elemental composition as an input data, and then applied to the set of unknown samples to evaluate their composition in a CF mode. The feasibility of such an approach is demonstrated by comparing the results obtained with classical LIBS (drawing calibration lines with a series of matrix-matched certified standards) and with independent measurements performed with a conventional technique (LA-ICP-MS).     

A nonlinear principal component analysis to study archeometric data

Statistical techniques, when applied to data obtained by chemical investigations on ancient artworks, are usually expected to recognize groups of objects to classify the archeological finds, to attribute the provenance of items compared with earlier investigated ones, or to determine whether an archaelogical attribution is possible or not. The statistical technique most frequently used in archeometry is the principal component analysis (PCA), because of its simplicity in theory and implementation. However, the application of PCA to archeometric data showed severe limitations because of its linear feature. Indeed, PCA is inadequate to classify data whose behavior describe a curve or a curved subspace of the original data space. As a consequence of it, an amount of information is lost because the multi‐dimensional data space is compressed into a lower‐dimensional subspace including principal components. The aim of this work is then to test a novel statistical technique for archeometry. We propose a nonlinear PCA method to extract maximum chemical information by plotting data on the smallest number of principal components and to answer archeological questions. The higher accuracy and effectiveness of nonlinear PCA approach with respect to standard PCA for the analysis of archeometric data are shown through the study of Apulian red figured pottery (fifth–fourth century BC) coming from some of the most relevant archeological sites of ancient Apulia (Monte Sannace (Gioia del Colle), Egnatia (Fasano), Canosa, Altamura, Conversano, and Arpi(Foggia)). Copyright © 2016 John Wiley & Sons, Ltd.