J. V. Gimeno Adelantado

FTIR quantitative analysis of calcium carbonate (calcite) and silica (quartz) mixtures using the constant ratio method. Application to geological samples.

A methodology for quantifying calcium carbonate (875 and 712 cm(-1)) and silica (798 and 779 cm(-1)) by FTIR spectroscopy applying the constant ratio method is proposed. The studied method is applied for quantitative analysis of calcite and quartz in geological samples. The suggested method uses potassium ferricyanide (2115 cm(-1)) as standard and samples are prepared as potassium bromide pellets, with statistically satisfactory results (relative standard deviation less than 5%). The influence of particle size (pulverised samples) on the accuracy of the results found by FTIR spectroscopy applying the constant ratio method has been studied. The granulometric study suggests that the homogeneity of particle size is important. An absorbances correction method is proposed to correct spectral interferences. Due to the fact that most spectra are characterised by a high number of absorbance peaks, spectral interferences may occur so that some peaks cannot be used for quantitative analysis. These interferences can be evaluated and eliminated with the proposed method and the peaks can be used in the analysis.

Fourier transform infrared spectroscopy and the analytical study of works of art for purposes of diagnosis and conservation

Abstract This paper is a study of the analytical capacity of Fourier transform infrared spectroscopy (FT-IR) for any type of samples from works of art. The analytical information obtained with this technique on organic and inorganic compounds is extremely useful in the preliminary studies necessary for diagnosis and to decide on the conservation process. This paper reports the analysis and study with FT-IR on samples extracted from the microlayers in several works of art from different periods (16th to 18th century) comprising wall paintings and canvas. The most outstanding of these being the frescoes by A. Palomino from two ceilings in the Santos Juanes church. The analytical procedures for the different components of the works studied such as 1. (a) varnish applied to wood panels and canvas paintings, 2. (b) binding media and pigments used by the artists, 3. (c) inerts, mortars, stuccos and grounds have been optimized. The FT-IR technique offers a quick analysis of microsamples (less than 0.5 mg) and is able to characterise the different molecular groups which provide information on the nature of the different materials of organic and inorganic origin used by the artist and thus permits the diagnosis of pathologies requiring conservation treatment.

Analytical evaluation of polyunsaturated fatty acids degradation during thermal oxidation of edible oils by Fourier transform infrared spectroscopy

Abstract The oxidative deterioration of polyunsaturated fatty acids (PUFAs) in culinary oils and fats during episodes of heating associated with normal usage (80–300°C, 20–40 min) has been monitored by Fourier transform infrared spectroscopy (FTIR). The thermal oxidation of PUFAs is a free radical chain reaction, in which hydroperoxides are generally recognized as the primary major products. Hydroperoxides of PUFAs are easily decomposed into a very complex mixture of secondary products with the decrease in unsaturation. The oxidative advance of PUFAs during heating was studied by the determination of unsaturation percentage at different temperatures and heating times. Oils frequently used in food frying such as olive oil, sunflower oil, corn oil and seeds oil (sunflower, safflower and canola seed) were studied. The results show there is a decrease in unsaturation starting at 150°C and becoming more pronounced at temperatures around 250°C. The following variations were found in the unsaturation percentage, expressed as methyl linoleate, between the original sample and the sample heated at 300°C for 40 min: olive oil (19–6%), sunflower oil (29–12%), corn oil (28–18%) and seeds oil (23–11%). This variation in unsaturation grade provides evidence of the transformation of essential PUFAs and subsequent decrease in the oils’ nutritional value. The internal standard method is suitably precise when the n-valeronitrile is used as standard as shown by the 1–2% relative standard deviation (R.S.D.) found for seven replicates.

Study of binding media in works of art by gas chromatographic analysis of amino acids and fatty acids derivatized with ethyl chloroformate

The aim of this work is to identify proteinaceous and oil binding media used in paintings from art collections in the Region of Valencia (Spain). This information is extremely useful for conservation and restoration work. The proposed procedure involves protein and glyceride hydrolysis from sub-milligram samples by treatment with hydrochloric acid, followed by neutralization, partition with chloroform and derivatization with ethyl chloroformate (ECF) of both the aqueous and the organic phases. The ECF derivatives of amino acids and azelaic, myristic, palmitic and stearic acids are separated by capillary gas chromatography. Amino acids are mainly found in the aqueous phase and long chain fatty acids in the organic phase. The distribution of azelaic acid was approximately similar in the two phases. Amino acid and fatty acid ratios found proved extremely useful for identifying the binding media in the paintings analysed.

Characterization of proteinaceous glues in old paintings by separation of the o-phtalaldehyde derivatives of their amino acids by liquid chromatography with fluorescence detection.

A HPLC-fluorescence method for characterization of proteinaceous glues from binding media used in pictorial works of art prior to conservation or restoration treatment is proposed. Fluorescence derivatization of amino acids released by acid hydrolysis of standard proteins is studied. The derivatization reagent was o-phtalaldehyde with 2-mercaptoethanol as catalyst. Mobile phase was a programmed gradient among two eluents (water buffered at pH 5.8 wit 5% THF, and methanol) and is able to satisfactorily resolve the amino acid derivatives in 45min. Peak area ratios among amino acid derivatives and the leucine derivative are useful to characterize the proteins. The method shows good sensitivity and adequate linearity between 2.0x10(-3) and 3.3mmol/l of each amino acid, with a limit of detection of 6.0x10(-4)mmol/l. The proposed method has been successfully applied to artistic samples from items of the cultural heritage of Valencia (Spain).

Analytical study by SEM/EDX and metallographic techniques of materials used in the iron production process during the Iberian period

Abstract This work is the archaeometric study of different types of materials used in iron production in the Iberian Period (6th–2nd century b.c.). The materials were recovered in several archaeological digs (which makes it possible to date the archaeological remains) on different sites in the Levante area of the Iberian Peninsula. The samples selected for this study belong to different materials used in the ancient iron production process such as ores, slags, finished objects, etc. The use of scanning electron microscopy (SEM) is proposed to observe surface images of the samples to determine their morphological, microstructural and topographic characteristics to obtain valuable information on the materials studied. The study also proposes chemical analysis of the elements in the sample by X-ray microanalysis (SEM/EDX) which provides both qualitative and quantitative information. The archaeometric study suggests that the iron obtained was very good quality, but the process was not economically efficient when viewed from todays perspective. Furthermore, the slag produced in the furnace can be related with the slag or impurities contained in the iron. It has also been possible to relate the ores and slag, some furnace conditions, the use of fluxes and also to differentiate types of slag.

Study and dating of medieval ceramic tiles by analysis of enamels with atomic absorption spectroscopy, X-ray fluorescence and electron probe microanalysis

Abstract This paper reports an analytical study of enamel on fragments of medieval tiles using atomic spectroscopy techniques — AAS, XRF and SEM/EDX. The samples came from a hermitage in the region of Valencia (Spain) and have different motifs, mainly floral ones in a wide variety of colors. A study of the soluble salts in the biscuits and mortar was carried out using AAS to determine their present capacity to produce efflorescence and the type of efflorescence. XRF was used to identify the oxides responsible for the different colors and the pigments used over large areas of the tiles (white and green). SEM/EDX was used to characterize the white and green and smaller areas of other colors. A correspondence between the different colors and tones and the metallic elements or mixtures was established. X-Ray energy spectra obtained for different areas of the same color have made it possible to quantify the contents of different elements, and thus to study the homogeneity of application. The presence of zinc is justified because of the physical and chemical properties it imparts to the enamels. The complementary nature of these spectroscopic techniques have made it possible to evaluate the state of conservation, to establish measures to clean the existing efflorescence according to their nature and to suggest dating of the materials.

Identification of drying oils used in pictorial works of art by liquid chromatography of the 2-nitrophenylhydrazides derivatives of fatty acids.

A new HPLC-UV-Vis method for identification of drying oils from binding media or protective film used in pictorial works of art prior to conservation or restoration is proposed. Chromophore derivatization of fatty acids released by hydrolysis of structural drying oils is studied. The derivatization reagent selected was 2-nitrophenylhydrazine with 1-ethyl-3-(3-dimethyl animopropyl)carbodiimide hydrochloride/pyridine as catalyst. This reaction was carried out using microwave heating. Mobile phase was methanol/water/n-propanol/acetic acid (80:14:5:1) running in isocratic mode. Absorbance was measured at 400nm. In these conditions, hydrazides of myristic, palmitic, oleic, and stearic acids were satisfactorily resolved. Method shows good sensitivity, with a detection limit of 15mumoll(-1), and good linearity between 0.03 and 3mmoll(-1). Peak area ratios among fatty acids derivatives allows identification of the drying oils. The stearic/palmitic ratio is the most important, because it allows to differentiate among the different drying oils. The proposed method has been successfully applied to real samples from items of the cultural heritage of Valencia (Spain).

Application of XRF, XRD, thermal analysis, and voltammetric techniques to the study of ancient ceramics.

Abstract. An in-depth chemical-analytical study has been performed on biscuit and mortar from 17th–18th century tiles from a mediaeval hermitage in the province of Valencia (Spain). Representative samples were chosen from the tile fragments available, using appearance, essentially color and consistency, as the criterion. The chemical composition was analyzed by X-ray fluorescence of the samples in the form of glass disks after a previous qualitative study to choose the standard materials for calibration and the experimental conditions used in the analysis. X-ray diffraction of the samples provided information about the mineralogical composition which was consistent with the firing of the original materials; it also gave information about the range of temperatures used in the firing. From thermal gravimetric analysis of the limestone, and from historical considerations, it was possible to deduce the raw materials used and their approximate composition in the tiles. In the same way it was possible to determine the nature of the mortars used to fix the tiles. Cyclic voltammetric study of the iron(II) and iron(III) system in the biscuit showed the simultaneous presence of both oxidation states, corroborating the results.

Fourier transform infrared spectroscopy and the analytical study of sculptures and wall decoration

Abstract An analytical examination of sculpture and wall painting, including several wooden polychromed carvings from Valencian churches (15th–17th centuries) using FT-IR spectroscopy is described. The organic and inorganic compounds used in the works of art and the different artistic techniques used in each historical intervention carried out in the sculptures are identified. The analytical information obtained with this technique on organic and inorganic compounds is extremely useful in the preliminary studies necessary for diagnosis and to decide on the conservation process.