Dominique Maria Scalarone

Ageing behaviour and pyrolytic characterisation of diterpenic resins used as art materials: colophony and Venice turpentine☆

Abstract The ageing behaviour of two diterpenic resins traditionally used as artists’ materials, colophony and Venice turpentine, was investigated with different spectroscopic and chromatographic techniques. In particular, three types of ageing (natural, artificial external conditions with a xenon lamp, artificial indoor conditions with fluorescent tubes) were applied to laboratory samples to study their effects on chemical structures. Thermally-assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GC/MS) was employed for careful characterisation and for identification of markers compounds on the vergin resins and in the course of ageing. The most significant changes were detected in the initial part of ageing, and the principal degradation products coming from oxidation, polymerisation and cleavage reactions identified. The high intensity of xenon lamp irradiation was found to cause, apart from oxidation and polymerisation reactions, further degradation of the chemical structure with molecular fragmentation. From the analytical point of view, the differentiation between colophony and Venice turpentine with THM-GC/MS appears to depend on differences in the lower molecular weight resin components.

Ageing behaviour and analytical pyrolysis characterisation of diterpenic resins used as art materials: Manila copal and sandarac

Abstract Artificial indoor and outdoor exposure conditions have been applied in order to investigate the photo-ageing behaviour of two natural resins once used as art materials. Copals and sandarac consist of free labdane diterpenoids and of a highly cross-linked fraction of polycommunic acid. To determine the nature and the composition of the cross-linked fraction, pyrolysis is required. Thermally assisted hydrolysis and methylation, coupled with gas chromatography–mass spectrometry (THM-GC/MS), has been used to identify the acidic compounds. Many secondary pyrolysis products have been recognised and distinguished from the original resin components. Further details on the composition and ageing behaviour of Manila copal and sandarac have been obtained from Fourier transform infrared spectroscopy (FTIR), size exclusion chromatography (SEC) and direct temperature-resolved mass spectrometry (DTMS). During ageing, cross-linking and cleavage reactions were found to affect largely the chemical structure of the two resins, together with minor degradation processes such as isomerisation, defunctionalisation and oxidation.

Advances in identification of plant gums in cultural heritage by thermally assisted hydrolysis and methylation.

AbstractPlant gums are present in works of art as binding media for watercolours and adhesives for cellulosic substrates. Thermally assisted hydrolysis and methylation (THM) in combination with analytical pyrolysis coupled to GC/MS has been applied to the characterisation of plant gums typically used in artworks. THM products from standard samples of arabic gum, tragacanth gum and cherry gum were characterised. The main products identified are permethylated and partially methylated aldonic acids, characteristic of specific epimeric sugars. Aldonic acids were formed by alkaline hydrolysis of free reducing sugars and of reducing polysaccharide terminal groups, while methylation occurs during pyrolysis. The presence of these characteristic markers allows gum identification. A systematic analysis of all the parameters that can affect the marker yields was performed. In particular, the influence of pyrolysis temperature, reagent concentration and contact time between tetramethylammonium hydroxide and sample were studied, and different kinds of sample preparation procedures were tested. Some analyses on real watercolours were performed, and gum binders were classified using the peak area ratio of the main monosaccharide markers. FigureClassification of gums on the basis of marker area peaks ratio

Thermally assisted hydrolysis and methylation-pyrolysis-gas chromatography/mass spectrometry of light-aged linseed oil

Abstract Drying and photooxidative ageing of thin films of linseed oil has been investigated under solar light accelerated ageing conditions by means of thermally assisted hydrolysis and methylation–pyrolysis–gas chromatography/mass spectrometry. The main pyrolysis product after the ageing process was found to be azelaic acid, in agreement with results reported in literature on naturally aged samples. The kinetic of azelaic acid formation during degradation has been determined from the pyrolysis experiments, and the results are fully compatible with those previously obtained by Fourier transform infrared spectroscopy. In this work the method for quantitative determination of azelaic acid from aged linseed oil, proposed by Chiavari et al., 1993 [G. Chiavari, G.C. Galletti, G. Lanterna, R. Mazzeo, J. Anal. Appl. Pyrolysis, 24 (1993) 227] is shown to be also valid under more strenuous ageing conditions than those occurring in typical indoor expositions.

Thermoresponsive mesoporous silica nanoparticles as a carrier for skin delivery of quercetin.

Recently, mesoporous silica nanoparticles (MSNs) have emerged as promising drug delivery systems able to preserve the integrity of the carried substance and/or to selectively reach a target site; however, they have rarely been explored for skin application. In this study, thermoresponsive MSNs, designed to work at physiologic cutaneous temperature, are proposed as innovative topical carriers for quercetin (Q), a well-known antioxidant. The thermosensitive nanoparticles were prepared by functionalizing two different types of matrices, with pore size of 3.5nm (MSNsmall) and 5.0nm (MSNbig), carrying out a free radical copolymerization of N-isopropylacrylamide (NIPAM) and 3-(methacryloxypropyl)trimethoxysilane (MPS) inside the mesopores. The obtained copolymer-grafted MSNs (copoly-MSNs) were physico-chemically characterized and their biocompatibility was attested on a human keratinocyte cell line (HaCaT). The release profiles were assessed and the functional activity of Q, free or loaded, was evaluated in terms of antiradical and metal chelating activities. Ex vivo accumulation and permeation through porcine skin were also investigated. The characterization confirmed the copolymer functionalization of the MSNs. In addition, both the bare and functionalized silica matrices were found to be biocompatible. Among the copolymer-grafted complexes, Q/copoly-MSNbig exhibited more evident thermoresponsive behavior proving the potential of these thermosensitive systems for advanced dermal delivery.

Plastic matters: an analytical procedure to evaluate the degradability of contemporary works of art

AbstractThe most significant results concerning a chemical study to evaluate the degradability of polymeric components in four contemporary works of art, partially or completely realized in plastics, are presented and discussed in this paper. The procedure applied is mainly based on the use of Fourier transform IR and UV–vis spectroscopies and pyrolysis–gas chromatography/mass spectrometry, and consists of the following steps: (1) compositional analysis of the artworks, with particular attention to components which may have a negative effect on the overall ageing; (2) evaluation of the actual state of conservation; (3) investigation of the accelerated ageing of reference polymer samples; and (4) monitoring of the natural ageing of the artworks. On such a basis, the following could be concluded. Stage Evidence by Loris Cecchini is made of poly(ether urethane) elastomer which contains a high amount of phthalates. Their exudation gives a sticky appearance to the artwork and their removal during ageing is the main cause of the loss of flexibility. The latex used by Andrés Pinal for tailoring Traxe de Home is a natural polyisoprene, whose oxidative degradation accounts for the extensive deterioration and yellowing of the artwork. The plaster sculptures of 3D Bodyscans 1:9 by Karin Sander are coated with an aliphatic epoxy resin. Its oxidation with formation of amides is the cause of the surface yellowing. The adhesive used by Dario Villalba for Tierra, Ladrillo y Agua is a commercial poly(vinyl acetate). Simulated photoageing suggests a fast deterioration due to deacetylation and cross-linking, which possibly is the main reason for the actual detachment of debris from the support. FigureInvestigated artworks from the Contemporary Art Museum of Santiago de Compostela (Spain), partially or completely realized in plastics

Synthesis and characterization of a hyper-branched water soluble β-cyclodextrin polymer

Summary A new hyper-branched water-soluble polymer was synthesized by reacting β-cyclodextrin with pyromellitic dianhydride beyond the critical conditions that allow the phenomenon of gelation to occur. The molar ratio between the monomers is a crucial parameter that rules the gelation process. Nevertheless, the concentration of monomers in the solvent phase plays a key role as well. Hyper-branched β-cyclodextrin-based polymers were obtained performing the syntheses with excess of solvent and cross-linking agent, and the conditions for critical dilution were determined experimentally. A hyper-branched polymer with very high water solubility was obtained and fully characterized both as for its chemical structure and for its capability to encapsulate substances. Fluorescein was used as probe molecule to test the complexation properties of the new material.

Effect of Multimodal Pore Channels on Cargo Release from Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles (MSNs) with multimodal pore channels were fully characterized by TEM, nitrogen adsorption-desorption, and DLS analyses. MSNs with average diameter of 200 nm with dual pore channel zones with pore diameters of 1.3ź2.6 and 4 nm were tested for their use in drug delivery application. Important role of the multimodal pore systems present on MSNs on the quantitative release of model drug ibuprofen was investigated. The results obtained revealed that the release profile for ibuprofen clearly shows distinct zones which can be attributed to the respective porous channel zones present on the particles. The fluctuations in the concentration of ibuprofen during the prolonged release from MSNs were caused by the multimodal pore channel systems.

Poly(NIPAM-co-MPS)-grafted multimodal porous silica nanoparticles as reverse thermoresponsive drug delivery system

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Pyrolysis–GC/MS for the identification of macromolecular components in historical recipes

AbstractAnalytical pyrolysis with thermally assisted hydrolysis and methylation was employed to investigate ancient ointments collected from Spanish vessels coming from the sixteenth century pharmacies. The ointments were reproduced on the basis of historical recipes and characterization was made in comparison with real samples. Characteristic markers indicate the presence of beeswax, of animal and plant lipids, and of natural resins. Analyses of old samples are consistent with the modern reproductions and with the analysis of raw materials. Multivariate data analysis was used to discriminate between the different types of lipidic materials, also in connection with their relative amount in the samples. FigureScore plot of principal component analysis performed on data obtained from real samples, reference ointments, and raw materials by means of thermally assisted hydrolysis and methylation