The use of polysaccharide rigid gels in cleaning treatments : multi analytical approach for the study of their performance, effectiveness and interference with paper artworks

The cleaning of paper artworks represents a fundamental treatment since external contaminants, metals, spores, etc. can promote degradation of cellulose (the principal constituent of paper). For this reason the removal of such components may partially preserve paper over time. Different cleaning treatments can be applied on paper artworks, for instance dried methods, aqueous cleaning systems. Recently polysaccharide rigid hydrogels (i.e: Agar and Gellan gum) have been used for the cleaning of paper, in order to increase surface wettability of paper and control the diffusion of water molecules in paper. This aspect represents an advantage especially in case of delicate surfaces and in presence of hydrophilic graphic media. The use of water (in a free or gelled form) may promote the extraction of hydrophilic components (either degradation products or original constituents of paper). Therefore the evaluation of the extraction of original constituents of paper induced by cleaning treatments as well as the evaluation of the effects of cleaning on chemical-physical properties of paper represents a relevant aspect in the context of paper conservation. For this reason the aim of the research is the evaluation of the extraction of sizing agents as gelatine contained in paper, products of hydrolysis of hemicelluloses and cellulose, induced by aqueous cleaning treatments and the evaluation of the effects of the cleaning on morphological, mechanical properties of paper. The study is carried out on paper artworks of different periods (from XVI to XX century) subjected to cleaning by immersion in distilled water and to application of Agar and Gellan gum rigid gels. GC-MS analysis show that such cleaning treatments can cause the extraction of products of hydrolysis of hemicelluloses and cellulose as well as the extraction of gelatine. This phenomenon is more evident in the case of the immersion of paper in distilled water and may partially explain the significant variation in the mechanical properties of paper observed by means of tensile testing after cleaning. In fact paper samples subjected to cleaning by immersion show a relevant decrease in the Ultimate Tensile Strength, probably correlated to the evident extraction of water in the free form of hemicelluloses products, and a relevant increase in the breaking strain (probably caused by the swelling of cellulose and the formation of hydrogen bonds between cellulose chains and water molecules). Such effect is reduced and a moderate improvement in mechanical properties of paper is observed when polysaccharide rigid gels are used. The application of rigid gel for the cleaning of ancient paper seems to be respectful of the original surface morphology of paper as well as in the case of the immersion treatment as revealed by 3D profilometer analysis and observation by stereo-microscope and SEM-EDS. On the contrary the application of dried methods (i.e.: wishab sponge) and cellulose ethers by means of cotton swabs, etc. may promote defibration and alteration in the morphology of paper surface because of the mechanical action induced by such applications. An analytical evaluation of the residues left by gels on paper after cleaning treatments is carried out by means of GC-MS analysis. Results show a reduced presence of gels residues left on paper only in the case of the application of 1% gel, because of its soft consistence and its difficult manipulation. The results obtained in this research demonstrate that the effects of cleaning are strongly dependent on the type of paper, its papermaking, its conservation and for this reason the choice of the most suitable method of cleaning should consider materials present in paper and properties of paper. For this reason chemical-physical analysis could be of great help for the knowledge of materials in paper and for the monitoring of cleaning treatments

Studio archeometrico dei dipinti murali di Spyros Papaloukas nel Duomo di Amfissa in Grecia

Il Duomo della città di Amfissa (Grecia) è stato costruito nel periodo 1859 – 1869. L’interno del Duomo è stato dipinto interamente dal pittore greco Spyros Papaloukas (1927 – 1932). Lo stato di conservazione della superfice dipinta attualmente versa in condizioni molto precarie ed in vista di un profondo intervento di risanamento e restauro e stata intrapresa una approfondita indagine diagnostica delle superfici dipinte. Allo scopo sono stati avviate una serie di controlli analitici e tecnologici. Nel caso degli intonaci dipinti, particolare attenzione è stata dedicata agli strati pittorici, alla composizione degli strati preparatori, alla caratterizzazione delle malte e ai problemi di deterioramento ad esse connesse. Frammenti di materiale pittorico sono stati analizzati mediante gascromatografia/spettrometria di massa per la ricerca dei leganti organici. E’ stato osservato materiale organico in tutti i campioni, in particolare olio di lino invecchiato e uovo. Dai dati analitici e dalle osservazioni in situ si ritiene che la particolarità dell’opera sia che l’intera superficie (1.500 m2 di superficie) sia stata dipinta con la tecnica pittorica murale “a secco”, adoperando esclusivamente dei leganti organici. Il quadro generale dei risultati delle indagini sui materiali inorganici insieme allo studio dei leganti organici ha rappresentato la base di riferimento per una mirata progettazione dell’ intervento conservativo necessario. Il presente lavoro fa parte del “International Multidisciplinary Conservation Project of the Holy Mary Annunciation Metropolitan Church of Amfissa (Greece)”

Determination of arachidonic acid metabolites in plasma by Micro-Extraction by Packed Sorbent coupled to Ultra-High Performance Liquid Chromatography-tandem mass spectrometry

Oxidative stress is defined as an imbalance between the production of reactive oxygen species (ROS) and antioxidant defenses. Oxidative stress is involved in several chronic diseases such as cardiovascular diseases, cancer, diabetes, neurodegenerative diseases, stroke condition and chronic inflammatory diseases. ROS and free radicals can induce lipid peroxidation of polyunsaturated fatty acids (PUFA), e.g. arachidonic acid, causing an alteration of the biological properties of phospholipidic membranes, such as increase of membrane’ permeability and inactivation of enzymes. In specific conditions, arachidonic acid can undergo alteration either by enzymatic peroxidation to form eicosanoids (i.e. prostaglandins, leukotrienes, and thromboxanes) via cyclooxygenase, lipoxygenase or cytochrome P-450 metabolic pathway, or by non-enzymatic peroxidation to form isoprostanes, malondialdehyde, 4-hydroxynonenal and other products. Biomarkers such as prostaglandins, isoprostanes and thromboxanes have been suggested to assess levels of oxidative stress and lipid peroxidation both in vitro and in vivo. The evaluation of oxidative damage is usually performed in serum, plasma and urine samples. The complexity of such biological matrices, deriving from the presence of interfering compounds (e.g. proteins and lipoproteins) and the tendency of auto-oxidation of lipids, makes the determination of oxylipins in such fluids difficult. The aim of this thesis was to develop and validate an analytical procedure for the simultaneous determination of different arachidonic acid metabolites in plasma. The method involved the use of an innovative technique based on the automated micro-extraction by packed sorbent (MEPS) coupled to an ultra-high performance liquid chromatography-electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) analysis. Fifteen compounds were selected as potential biomarkers of oxidative stress and determined: 8-iso prostaglandin F2α (8-isoPGF2α), prostaglandin E2 (PGE2), 8-iso prostaglandin E2 (8-isoPGE2), Prostaglandin D2 (PGD2), thromboxane B2 (TX-B2), leukotriene B4 (LEU-B4), 15-deoxy-Δ12,14-Prostaglandin J2 (15-deoxy-PJ2), 20-hydroxy-5Z,8Z,11Z,14Z-eicosatetraenoic acid (20-HETE), (±) 15-hydroxy-5Z,8Z,11Z,13E-eicosatetraenoic acid (15-HETE), (±) 12-hydroxy-5Z,8Z,10Z,14Z-eicosatetraenoic acid (12-HETE), (±) 5-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-HETE), (±)14(15)-epoxy-5Z,8Z,11Z-eicosatrienoic acid (±14,15-EET), (±)11(12)-epoxy-5Z,8Z,14Z-eicosatrienoic acid (11,12-EET), (±)8(9)-epoxy-5Z,11Z,14Z-eicosatrienoic acid (8,9 EET), (±) 13-hydroxy-9Z,11E-octadecadienoic acid (13-HODE). After the optimization of instrumental parameters, stability assays performed at 4 °C for one month and at room temperature for 24 h showed that all analytes were stable in water solution for at least 1 month at 4 °C and for 24 h at room temperature except PGD2 and isoprostanes that were stable respectively for 24 h and 14 days at 4 °C and PGD2 that resulted stable until 6 hours at room temperature. Protein precipitation, involving the use of acetonitrile and saline solution of copper sulphate pentahydrate (10% w/v) and sodium tungstate dehydrate (12% w/v), and ultrafiltration (with a 3kDa cut-off) approaches were tested in order to find a reliable and effective sample clean-up method. The use of copper sulphate (sol.A) and sodium tungstate solutions (sol.B) (plasma:solA:solB, 2:1:1 v/v/v) and the subsequent addition of acetonitrile (plasma:acetonitrile, 1:1 v/v) produced clearer extracts without significantly impacts on the recovery of analytes. The extract was subjected to MEPS procedure to further remove interferences and to pre-concentrate the target analytes. Regardless of the analytes concentration, the procedure showed an almost quantitative recovery for most compounds (8-iso-PGF2α, 8-iso-PGE2 90-120 %; PGE2 85-100%; TX-B2 85-100%; Leu 80-105%; 13-HODE 98-130%; 15-deoxy-PJ2 90-105%; 12-HETE 80-108%; 14,15-EET, 11,12-EET, 8,9-EET 60-104%; 20-HETE, 15-HETE, 5-HETE 60-110%), and a low intra- and inter-day variability (relative standard deviation close to 15%). Matrix effect was evaluated by comparing the slopes between calibration curves obtained with working solution and in matrix (at a confidence level of 95%). Linear calibration ranges (R2 >0.995) over three orders of magnitude were observed for all the analytes. The variability induced by the sample preparation, the extraction and instrumentation was minimized by the addition of a set of deuterated internal standard (PGE2-d4, 20-HETE-d6, 14(15)-EET-d11, 8-iso-PGE2-d4, 8-iso-PGF2-d4), thus improving the analytical performances. Future application will be devoted to assess the levels of these arachidonic acid metabolites in patients affected by ischemic and hemorrhagic stroke and healthy patients in order to evaluate potential relationship between the selected compounds and type of stroke diseases and to evaluate the possibility to use such analytes to predict the onset of such diseases

Dipinti sottoposti a foderatura: lo stato di conservazione

Sei dipinti (opere di E. Tito, F.P. Michetti, A. Mancini, G. Sacheri, E.Rizzi) della Galleria d'Arte Moderna Ricci Oddi di Piacenza sono stati studiati, in quanto presentavano delle problematiche conservative, dovute ad un peggioramento dell'adesione degli strati pittorici e della preparazione dal supporto. Tale fenomeno è stato osservato in particolar modo su alcune opere sottoposte in passato ad interventi di foderatura. L'obiettivo del lavoro è stato quello di valutare quanto la foderatura possa avere contribuito a determinare le problematiche conservative riscontrate, in relazione alle caratteristiche del supporto tessile, al tipo e alla spessore dello strato preparatorio, al tipo di legante organico utilizzato nel film pittorico e pigmenti, considerando anche l'aspetto ambientale (interazione tra materiali e condizioni di temperatura ed umidità presenti nella galleria). A tal fine si è considerato fondamentale intervenire con una campagna di indagini scientifiche volte alla caratterizzazione dell'adesivo, della tecnica pittorica, del tipo d fibra presente nelle tele. In particolare, questo studio riporta le indagini volte a verificare la presenza di colla pasta, colla d'amido o colla animale, attraverso la caratterizzazione chimico-fisica dell'adesivo. A tal fine, sono stati prelevati campioni dalla tela risvoltata nel retro del telaio, ed effettuate indagini mediante spettroscopia FT-IR; Test con reattivo di Lugol, gascromatografia accoppiata alla spettrometria di massa (GC-MS). I risultati delle indagini effettuate hanno indicato la presenza di una colla mista (colla d'amido e colla animale) nei campioni prelevati dalla tela di foderatura

Cleaning painted surfaces: evaluation of leaching phenomenon induced by solvents applied for the removal of gels residues

Cleaning is one of the most important, delicate at the same time controversial processes belonging to the conservation treatment of paintings. Although a strict definition of cleaning would be the removal of dirt, grime, or other accretions (surface cleaning), in the conservation field, cleaning is used in the broader meaning to include thinning/removing altered or “unwanted layers” of materials without damaging or altering the physico-chemical properties of the surfaces to be preserved. The cleaning of unvarnished paintings is one of the most critical issues that are currently discussed. Different cleaning tools, such as gels, soaps, enzymes, ionic liquids, and foams, as well as various dry methods and lasers, but only a few studies have been performed on the risk associated with the use of water and organic solvents for the cleaning treatments in relation to the original paint binder. The aim of the study is to verify analytically the behavior of water gelling agents during cleaning treatments, and the interaction of the following elements: water or organic solvents applied for the removal of gel residues with the original lipid paint binder. For this purpose the study was conducted on a fragment of canvas painting (XVI-XVII century) of Soprintendenza per i Beni Storici, Artistici ed Etnoantropologici del Friuli Venezia Giulia (Superintendence for the Historical, artistic and ethno-anthropological heritage of Friuli Venezia Giulia), Udine by means of Fourier Transform Infrared Spectroscopy, Gas Chromatography/Mass Spectrometry, and Scanning Electron Microscopy

The painting technique of Konrad Witz: An example of experimentation with innovative materials in 15th century

Konrad Witz represents an artist of great interest having worked in a period (first half of 15th century) of experimentation of materials, in the field of painting. The four paintings on wooden panels, kept at the Musée d'Art et d'Histoire in Genève (Switzerland), are a clear example of the artist’s will to pay attention to detail, to the brilliance of colours and to shades. A multi-analytical approach was applied in order to obtain information about materials, the technique used by the artist and the state of conservation of the four paintings, with the perspective of a restoration work. This purpose was achieved thanks to the application of non-invasive techniques, i.e. in situ X-ray fluorescence (XRF) through portable instrument, and micro sampling for Scanning Electron Microscopy coupled to microanalysis (SEM-EDS), micro Fourier Transform Infrared Spectroscopy (FTIR) and Gas-Chromatography coupled to Mass Spectrometry (GC–MS) analyses. Results showed the presence of a mixed technique “grease tempera” and the artist’s research in the use of innovative materials and technique for that period, i.e. the presence of small glassy violet particles inside a red lacquer layer, made of silicon, aluminium, potassium, sodium and manganese, as revealed by XRF and SEM-EDS analyses

An evaluation of changes induced by wet cleaning treatments in the mechanical properties of paper artworks

Wet cleaning of ancient papers is a common treatment performed for the removal of degradation products, external contaminants and salts, which can promote the degradation of cellulose (i.e., hydrolysis, oxidation). In this research, the effects on the mechanical properties of paper samples caused by wet cleaning treatments were evaluated by considering the changes induced in the ultimate tensile strength, deformation at break and flexibility. For this purpose, samples were subjected to different aqueous cleaning treatments such as immersion in deionised water and the application of rigid gels of agar and gellan gum at different concentrations was carried out. Tensile tests were run, and morphological observations of paper by means of light microscopy and scanning electron microscopy were recorded. Contrary to the significant changes in the mechanical properties of paper samples after immersion treatment (an increase in flexibility as the elongation at break), the use of gelled systems caused slight improvement in the mechanical properties of paper (in both the ultimate tensile strength as well as in the breaking strain). Changes in the mechanical properties of paper were also correlated with slight changes in the diameter of the cellulose fibres as a consequence of the swelling action of water molecules, especially in the case of immersion treatment. Finally, the tensile tests performed on the paper samples after thermohygrometric accelerated artificial ageing (70 C and 65 % RH) demonstrated that cleaning treatments by rigid gels did not seem to accelerate any sort of paper degradation in the mid to long term