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This paper presents results from ongoing investigations of soft and dripping oil paint in art works by CoBrA's Karel Appel (1921-2006) and Asger Jorn (1914-1973). The work is part of the PhD-projec ...

The painting C’est grace a nous by Asger Jorn shows unusually soft black paint with substantial delamination. To provide insight into the condition and conservation issues, samples were analysed using Fourier-transform Infrared Spectroscopy (FTIR), Direct temperature Mass Spectrometry (DTMS) and Scanning Electron Microscopy Energy Dispersive X-ray Spectroscopy (SEM-EDX). The results show that the oil medium of the black paint layer in contact with the zinc containing ground has contributed to the development of zinc fatty acid salts (zinc soaps). Examination of the painting confirmed that the paint delamination was mainly found where the black paint was unusually soft. The implications for delamination and considerations for a possible consolidation treatment of C’est grace a nous are discussed in the context of the analytical results.

Moisture is a driving factor in the long-term mechanical deterioration of canvas paintings, as well as for a number of physico–chemical degradation processes. Since the 1990s a number of publications have addressed the equilibrium hygroscopic uptake and the hygro-mechanical deformation of linen canvas, oil paint, animal glue, and ground paint. In order to visualise and quantify the dynamic behaviour of these materials combined in a painting mock-up or reconstruction, we have performed custom-designed experiments with neutron radiography and nuclear magnetic resonance (NMR) imaging. This paper reports how both techniques were used to obtain spatially and temporally resolved information on moisture content, during alternate exposure to high and low relative humidity, or in contact with liquids of varying water activities. We observed how the canvas, which is the dominant component in terms of volumetric moisture uptake, absorbs and dries rapidly, and, due to its low vapour resistance, allows for vapour transfer towards the ground layer. Moisture desorption was generally found to be faster than absorption. The presence of sizing glue leads to a local increase of moisture content. It was observed that lining a painting with an extra canvas results in a damping effect: i.e. absorption and drying are significantly slowed down. The results obtained by NMR are complementary to neutron radiography in that they allow accurate monitoring of water ingress in contact with a liquid reservoir. Quantitative results are in good agreement with adsorption isotherms. The findings can be used for risk analysis of paintings exposed to changing micro-climates or subjected to conservation treatments using water. Future studies addressing moisture-driven deformation of paintings can make use of the proposed experimental techniques.

Easel paintings on canvas are subjected to alteration mechanisms triggered or accelerated by moisture. For the study of the spatial distribution and kinetics of such interactions a moisture exposure chamber was designed and built to perform neutron radiography experiments. Multilayered sized and primed canvas samples were prepared for time resolved experiments in the ICON cold neutron beamline. The first results show that the set up gives a good contrast and sufficient resolution to visualise the water uptake in the layers of canvas size and priming. The results allow for the first time real time visualisation of the interaction of water vapour with such layered systems. This offers important new opportunities for relevant spatially and time resolved material behaviour studies and opens the way towards numerical modelling of the process. These first results show that cellulose fibres and glue sizing have a much stronger water uptake than the chalk–glue ground. Additionally it shows that the uptake rate is not uniform throughout the thickness of the sized canvas. With prolonged moisture exposure a higher amount of water is accumulating at the lower edge of the canvas weave suggesting a decrease in permeability in the sized canvas with increased water content.

Descente des vaches (1836) by Theodore Rousseau in the Mesdag Collection in The Hague is barely readable and its paint layers are in poor condition. The surface of the painting is strongly deformed and cracked, the whole painting has darkened and especially the greens have lost all or most of their colour resulting in brown passages. Large passages of the painting that were painted with multiple thick and medium-rich layers have darkened dramatically. This paper proposes that the degradation of Emerald green (Cu(C2H3O2)(2)center dot 3Cu(AsO2)(2), copperacetoarsenite) - the main green pigment used in this painting - is a significant factor in the cause of the darkening. Electron backscatter images reveal that the Emerald green particles are shown different degrees of degradation: from partially to completely disintegrated. Elemental maps show that arsenic is distributed throughout the paint cross section, with relatively higher concentrations around iron-and aluminium-containing particles, and in the varnish layer. Imaging-Fourier-transform infrared microscopy detects copper soaps in the degraded Emerald green-containing layers. Analytical data from four paint cross sections strongly suggest that Emerald green reacts with free fatty acids derived from the binding medium forming copper soaps and mobile arsenic-based species. Chemical laboratory experiments fully support this hypothesis. Emerald green and palmitic acid in chloroform form copper palmitate and arsenic trioxide (arsenolite, cubic) under room temperature and normal light conditions. The degradation of Emerald green particles in Descente des vaches has resulted in a loss of light-reflecting surfaces and in newly formed compounds in the paint, both contribute to the colour change from green to brown.

The study of the early oeuvre of the Swiss painter Cuno Amiet (1868–1961) has revealed that, up to 1907, many of his grounds were hand applied and are mainly composed of chalk, bound in protein. These grounds are not only lean and absorbent, but also, as Synchrotron radiation X-ray microtomography has shown, porous. Our approach to the characterization of pore structure and quantity, their connectivity, and homogeneity is based on image segmentation and application of a clustering algorithm to high-resolution X-ray tomographic data. The issues associated with the segmentation of the different components of a ground sample based on X-ray imaging data are discussed. The approach applied to a sample taken from “Portrait of Max Leu” (1899) by Amiet revealed the presence of three sublayers within the ground with distinct porosity features, which had not been observed optically in cross-section. The upper and lower layers are highly porous with important connectivity and thus prone to water uptake/storage. The middle layer however shows low and nonconnected porosity at the resolution level of the X-ray tomography images, so that few direct water absorption paths through the entire sample exist. The potential of the method to characterize porosity and to understand moisture-related issues in paint layer degradation are discussed.

The depth-profiles of aged triterpenoid resin films, dammar and mastic, were uncovered by optimized krypton fluoride excimer laser ablation (248 nm, 25 ns) and the etched varnishes were examined by high performance size exclusion chromatography (HP-SEC). The use of two detectors monitored the molecular weight distribution across depth as a function of absorbance at ultraviolet (240 nm) and visible (400 nm) light. The absorption of the films at both wavelengths is separated in a small fraction of sesquiterpenoids (200 Da), triterpenoid molecules (400/500 Da), dimerized and oxidized triterpenoid molecules (900–1000 Da) and condensed entities (10–80 kDa) that are formed upon the radical polymerization of polycadinene and cis-1,4-poly-β-myrcene, which are the polymers of dammar and mastic, respectively. The results establish the generation of depth-dependent gradients in radical polymerization, condensation and cross-linking across the depth-profiles of the triterpenoid films as a consequence of aging.

Scanning electron microscopy backscattered-electron images of paint cross sections show the compositional contrast within the paint system. They not only give valuable information about the pigment composition and layer structure but also about the aging processes in the paint. This article focuses on the reading of backscatter images of lead white-containing samples from traditional oil paintings (17th–19th centuries). In contrast to modern lead white, traditional stack process lead white is characterized by a wide particle size distribution. Changes in particle morphology and distribution are indications of chemical/physical reactivity in the paint. Lead white can be affected by free fatty acids to form lead soaps. The dissolution of lead white can be recognized in the backscatter image by gray (less scattering) peripheries around particles and gray amorphous areas as opposed to the well-defined, highly scattering intact lead white particles. The small particles react away first, while the larger particles/lumps can still be visible. Formed lead soaps appear to migrate or diffuse through the semipermeable paint system. Lead-rich bands around particles, at layer interfaces and in the paint medium, are indications of transport. The presence of lead-containing crystals at the paint surface or inside aggregates furthermore point to the migration and mineralization of lead soaps.

Naples yellow-containing oil paints aged under natural and artificial conditions were investigated as model systems to evaluate the potential of secondary ion mass spectrometry (SIMS) when used in combination with other mass spectrometric and spectroscopic analytical methods. Although the advantage of SIMS is the simultaneous detection of organic and inorganic components and their spatial distribution, the methodology has limitations in compound sensitivity and shows bias towards certain constituents. Gas chromatography–mass spectrometry (GC/MS) shows dicarboxylic fatty acids to be main components in the paint, but SIMS detects these compounds poorly. Electrospray ionisation mass spectrometry (ESI-MS) shows a broad range of glyceryl derivatives of mono- and dicarboxylic fatty acids (mono-, di- and triglyceride derivatives), while SIMS only detects the mono- and diglycerides of the monocarboxylic acids. Compared to SIMS, direct temperature-resolved mass spectrometry (DTMS) offers greater insight into how the various constituents are incorporated into the paint film, but SIMS data supports the information provided by Fourier transform infrared (FTIR) on metal soap formation. The surface sensitivity of SIMS is an advantage for probing paint constituent distributions and was exploited to examine variations in the composition of the top and bottom of a paint film, and the spatial correlation between metal and fatty acid composition in metal soap aggregates. Disadvantages of SIMS are the low yields and matrix dependency of the organic species in the paint matrix. Application of an ultra-thin gold coating overcomes this, and enhances the organic secondary ion yields leading to more accurate spatial distribution.

An analytical mass spectrometric method was developed for the comprehensive characterization of the poly(ethylene glycol) (PEG) based additives present in water extracts of acrylic emulsions, acrylic emulsion paints and samples from paintings. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used to determine the molar mass distribution (MMD), i.e., the weight average molar mass, number average molar mass and the polydispersity characteristics of the PEG compounds. Nano electrospray ionisation mass spectrometry (ESI-MS) was used to determine the end-group structures. It was possible to determine both end-groups of the PEG compounds using ESI-MS in combination with nozzle skimmer dissociation (NSD) and tandem MS (MSMS). The method development is part of a larger project of analysis of artists’ paints and samples from paintings reported elsewhere. The new methodology is demonstrated here with two relevant examples of a often used PEG and an acrylic medium.

The depth profiles of aged dammar and mastic films, which were uncovered by optimized KrF excimer laser ablation (248 nm, 25 ns), were examined by direct temperature-resolved mass spectrometry (DTMS). The results establish the generation of depth-dependent compositional gradients in triterpenoid resins as a consequence of aging, for the first time on the molecular level. Electron ionization DTMS total ion currents show that the required temperature to volatilize the polar compounds and the relative amount of pyrolysis products of the high molecular weight condensed fraction is reduced when the upper layer of varying thickness of the films had been removed by the laser. The relative abundance of characteristic ion fragments of known oxidized triterpenoid compounds gradually decreased with depth. In contrast, the ion fragments of original resin molecules became more abundant with depth. The mass spectra of the bulk of the films resembled that of the control samples, which were not subjected to aging. Multivariant factor discriminant analysis quantified the oxidative gradients and showed that a depth of 15 μm from the surface of the aged films is the threshold between highly and much less deteriorated material.

Poly(ethylene glycol) (PEG) compounds in artists’ acrylic emulsion paint products from different paint manufacturers, ranging from base emulsions (Rohm and Haas, Rohm and Scott Bader), to modified emulsions and complete paints (Rowney, Winsor and Newton, Golden, Liquitex, Lascaux), were characterised with a newly developed mass spectrometric method which combines data from Matrix assisted laser desorption/ionisation mass spectrometry (MALDI–MS) and nano-electrospray ionisation mass spectrometry (nano-ESI–MS(MS)). MALDI–MS was used for the determination of the molar mass distribution (MMD) and calculation of the molar mass averages ( M w and M n ), the polydispersity index ( D ) and the relative amount of a specific distribution if multiple PEGs were present. Electrospray ionisation mass spectrometry was used for the end-group analysis. Three different classes of polymers was found being PEG, polypropylene glycol (PPG) and a block copolymer of polyethylene glycol/polypropylene glycol (PEG/PPG) with molar mass averages ranging from 400 to 4200 Da. PEG compounds with a nonylphenyl or an octylphenyl hydrophobic end-group are most common. The hydrophilic end-groups observed are hydroxide and/or sulphate. Water extracts of microsamples from a palette by David Hockney dating from 1970 and samples paintings by Patrick Caulfield (1936–2005) and John Hoyland (born in 1934) were investigated with the same technique. Although some artist paint manufacturers use the same specific base emulsions to make their paints, the composition of the PEG compounds present in the water extracts of the palette and paintings samples made it possible, in some cases, to suggest a specific brand of paint used by the artist.

Cholesterol (1) constitutes approximately 5% of the lipid fraction of eggs. The compound is therefore abundant in fresh egg tempera paints. The fate of cholesterol upon light ageing of egg tempera paint binding medium was investigated by direct temperature resolved mass spectrometry (DTMS) and tandem mass spectrometry (DTMSMS). Cholesterol oxidation products (COPs) such as 5,6-epoxycholestan-3-ol (2) and 3-hydroxycholest-5-en-7-one (3) were positively identified in light-aged egg binding medium. Given the fast rate of oxidation of cholesterol, the corresponding oxidation products are better markers for egg tempera than the cholesterol molecule itself. Cholesterol and COPs were discovered in paints on German baroque altar pieces from the 16th and 18th C and in a 20th C glaze on a Mark Rothko Seagram Mural painting at Tate by DTMS fingerprinting analysis of paint microsamples.

Lead soap aggregateshave been-found in lead-containing oil paint layers in paintings from the thirteenth to the twentieth century. They severely affect the stability of the paint layers and disturb the surface of the paintings. Paint cross-sectionsfrom five paintings affected by lead soaps were selected to illustrate and investigate this degradation phenomenon with the analytical imaging techniques of Fourier transform infrared spectroscopy, secondary ion mass spectrometry and scanning electron microscopy combined with X-ray analysis. Examples aregiven of lead soapsforming in a mature paint system or, alternatively, in the early drying stage of the oil; lead soapsforming from various types of lead-containing pigments or driers; lead soapsforming in multiple paint layers; and lead-containing crystallization products inside aggregates. The phenomenon of lead soap aggregatesis multifaceted, and one general scenario describing theformation of lead soap aggregatescannot explain all aspects. However, th...

The current project describes physical and chemical alterations that result from the thermal exposure of sunflower achenes and seeds. Specifically, achenes and seeds were heated at temperatures ranging from 130 to 600 °C under anoxic conditions for 60 min. Changes were measured in mass, relative percentages of C and N, internal and external morphology, molecular composition by direct temperature-resolved mass spectrometry (DTMS) under EI conditions, and the reflectance on polished specimens. The main constituents of sunflower seeds are lipids and protein, while the pericarps or hulls enclosing the seeds have a ligno-cellulosic structure. The morphology of achenes and seeds remains intact following exposure which makes the identification of the residues possible. The results of the sunflower experiments were compared to previous experiments conducted with peas and wheat grains. Up to approximately 340 °C, the molecular conversion of polysaccharide and protein rich peas and wheat grains follow similar pathways, while the lignin present in sunflower achenes follows its own unique pathway, resulting in a different molecular composition. At higher temperatures the molecular composition of the three propagules becomes identical. In addition the reflectance of the three propagules is identical confirming the similarity in molecular composition. Lipids show a different behaviour compared to the other three biopolymers; from 370 °C no oils are observed in the heated specimens and the DTMS-EI measurements show no lipid markers. Apart from evaporation of the triacylglycerides it is suggested that steroids have a high resistance against thermal degradation and are converted into aromatic moieties.

The chemical characterisation of solid organic residues found in ceramic vessels, can provide archaeologists with valuable information about ancient diets. Although several selective analytical techniques have been applied to the analysis of specific classes of compounds, such as extractable lipids, waxes, terpenoids and protein fragments, a non-selective analytical technique is required to characterise and categorise complete solid organic residues. In this study, Direct Temperature-resolved Mass Spectrometry (DTMS) is used for the characterisation of 34 solid residues situated on vessels recovered from an indigenous settlement from the Roman period at Uitgeest – Groot Dorregeest (The Netherlands). Sample preparation is limited to grinding very small samples (5–10 μg) and suspending them in water. DTMS analysis of aliquots (1–2 μL) of this suspension gave information about a broad range of organic compounds, such as lipids, polynuclear aromatic hydrocarbons, markers for residual proteins and polysaccharides, and for newly formed complex condensed polymers. Multivariate analysis of the DTMS spectra identified five different chemotypes: groups of residues with comparable chemical characteristics. The biomolecular origin of each of these chemotypes is identified by comparison with experimentally charred reference materials. The chemotypes A1 and A2 consist of charred residues identified as starch-rich foods (mixed with animal or plant products), chemotype C consists of protein-rich charred animal products without starch, chemotype B contains smoke condensates from wood fires, and chemotype D consists of special protein-rich and lipid-free foods or non-food products.

This paper describes natural aging processes in the seventeenth-century oil paintings from the Oranjezaal ensemble in the Huis ten Bosch Palace (The Hague). Degradation of a wide range of pigments – lead white, lead-tin yellow, minium, smalt, azurite, ultramarine, vivianite, orpiment, vermilion, bone black, organic lakes, indigo and Kassel earth – in oil paints is discussed. In this unique case of an ensemble kept under known conditions and with similar restoration histories, it was possible to relate the degree of aging to differences of quality of pigment and binding medium and the ways the artists applied their materials.

A nineteenth-century mummy pigment (Hafkenscheid paint material collection) was analysed by direct temperature-resolved mass spectrometry (DTMS) and gas chromatography/mass spectrometry (GC/MS, Py-GC/MS, Py-TMAH-GC/MS). Megilp and asphalt (Hafkenscheid collection) reference samples were analysed under similar conditions. The mummy pigment investigated is complex. Py-GC/MS data indicated a pre-treated asphalt, i.e. only (di)benzothiophene- and traces of hopane-asphalt markers were left in the sample. DTMS, GC/MS and Py-TMAH-GC/MS results for the pigment pointed to the presence of slightly aged mastic resin and conifer resin and a complex lipid fraction. A poorly oxidized linseed oil and additions of beeswax, seen as long chain normal fatty acids, and another fat of a bacterial, fungal or human origin showing myristic acid, C6:1-C16:1 and C18:1 mono-unsaturated fatty acids, iso and anteiso fatty acids were found. The main components, mastic resin and linseed oil, suggest a megilp combined with a bla...

Imaging secondary ion mass spectrometry (SIMS) is applied for the first time to paint cross sections with degraded vermilion (red mercury sulfide) paint to cast new light on the well-known problem of its light-induced darkening. The static SIMS data are combined with light microscopic, electron microscopic studies and energy-dispersive X-ray analysis to identify and localize the various reaction products. The spatial distribution of atomic and molecular species in paint cross sections of the native vermilion and the reaction products leads to the formulation of a new hypothesis on the reaction mechanism of the photodegradation of vermilion where two black and white reaction products are formed sequentially. Under the influence of light, some of the vermilion (HgS) is converted into Hg(0) and S(0). In this process, the chlorine ions, present in the native vermilion, act as a catalyst. We propose that the Hg(0) is deposited on the surface of the remaining HgS as elementary mercury nanoparticles, which turns the vermilion black. Chloride, derived from an external source, is accumulating in the black phase. The metallic mercury and the remaining HgS react away with the excess of chloride. Two intermediate products and a white end product, mercuric chloride (HgCl2), are formed.

Matrix-Assisted Laser Desorption/Ionization Time-of-Flight mass spectrometry (MALDI-TOF-MS) on cellulosic surfaces is shown to be a suitable method for examining highly oxidized terpenoids, which are otherwise too difficult to determine by other techniques. By crystallization of a 2,5-dihydroxybenzoic acid (DHB) matrix and the sample solution on cellulose-coated thin layer chromatography(TLC) plates, spectra with good signal/noise ratios are obtained and no significant interferences due to matrix ions or cluster ions were produced, at least not in the range of m/z values of interest (>300 Da). The validity of the method was tested on natural di- and triterpenoid resins used as paint varnishes by Old Masters. The samples were analyzed before and after artificial light ageing. Di- and triterpenoid compounds, being very sensitive towards photo-oxidation, were found as oxidized molecules even in the raw resins and in the unexposed varnish layers. Artificial ageing simulating window-filtered daylight resulted in a stronger oxidation of the original terpenoids and the incorporation of up to six oxygen atoms per molecule could be demonstrated. Terpenoid dimers and their oxidation products were also detected.

Describes the changes in the infrared spectra of oil paint as a result of ageing. The focus is on the influence of pigments on the long term changes in the oil binding medium. Several naturally aged paints made with different pigments were analysed using Fourier-transform infrared spectroscopy (FTIR). One of the most pronounced effects observed in the infrared spectra of ageing paint is the shifting and broadening of the carbonyl band due to the formation of carboxylic acids. Another effect of pigments on the oil binding medium is the catalysis of the hydrolysis of triglycerides, as indicated by the increasing intensity of the ester absorption. Finally, the nature of the pigments included has a profound effect on the CH strength absorptions. From these results it is clear that pigments can significantly alter the infrared spectra of drying oil, and should therefore be identified to ensure correct assessment of the infrared spectra in the drying paint.

A whitish deterioration product was observed on the dark paint in a number of large-scale oil paintings that are part of the Oranjezaal interior decoration in the Royal Palace Huis ten Bosch (The Hague). The whitened areas of a painting by Pieter Soutman dating from 1648 were micro-sampled and compared with “healthy” black paint using different analytical imaging techniques. The dark paint was identified as bone black in linseed oil with a lead drier added. Microscopic images of the cross-section revealed a white top layer of 10–20 μm in the black paint layer. Imaging the cross-section surface with scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) and specular reflection Fourier transform infrared (FTIR) showed homogeneous distributions of phosphate, phosphorus and calcium over the black and the white degraded bone black. X-ray diffraction (XRD) showed the presence of calcium phosphate hydrate (Ca 3 (PO 4 ) 2 · x H 2 O), monetite (CaHPO 4 ) with possibly some poorly crystalline or amorphous hydroxyapatite (Ca 5 (OH)(PO 4 ) 3) . The EDX maps of lead and carbon, however, showed some discontinuity between the degraded and non-degraded bone black. There was an increase in the lead concentration in the white top layer, and a slight decrease of carbon. Transmission FTIR demonstrated that aromatic network polymers from the carbon black are markedly diminished in the white deterioration product. It is proposed that the carbonized organic matter in the bone black is vulnerable to photo bleaching in the presence of a lead catalyst under these circumstances.

The main churches of two important monasteries in Thessalia, Central Greece, are decorated with wall paintings that hail from the post-Byzantine period. The mural decoration of the main church of the St. Byssarionas Monastery at Doussiko has been attributed to the iconographer Tzortzis. The same painter is believed to have also operated in the main church of the Transfiguration Monastery at the monastic community of Meteora. The light microscopic (LM) examination of the cross-sections of samples taken from the gilded areas of the wall paintings, together with the direct temperature resolved mass spectrometric (DTMS) and scanning electron microscopy-energy dispersive X-ray spectroscopic (SEM-EDX) analysis, revealed a further resemblance of the materials and the methodology employed. The gold leaf was applied to the paintings by means of a mordant, which contains linseed oil mixed with a lead-containing dryer and an earth pigment or clay. The present study can constitute additional evidence to reinforce the idea that the two churches may have been painted by the same painter or workshop.

Artists’ acrylic emulsion paints are formulated using many constituents. Non-ionic surfactants such as those based on polyethylene oxides (PEOs) have been found in acrylic paint films, which may function both to stabilize the acrylic polymer in the aqueous emulsion phase and to aid pigment wetting and dispersion. PEOs that remain relatively mobile in the dried polymer film may affect surface gloss in a painting, the extent and nature of dirt pick-up, and the sensitivity of the film to methods used for surface cleaning. The present study aimed to characterize the migration of PEO surfactant in selected contemporary acrylic emulsion paints made by Winsor & Newton and Golden Artist Colors, and to assess the effects of swab-rolling with water and non-polar solvent, used for surface cleaning paintings, on dried and light-aged paint films. Methods for characterization included light microscopy (LM) and scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and matrix assisted...

Several traditional paint samples were prepared for infrared spectroscopic analysis in a number of different ways. The methods applied include the formation of KBr pellets, squeezing of dissected or multi-layer samples in a diamond cell, embedding in a modern resin, and a new method in which a paint cross-section is embedded in KBr and polished from both sides to obtain a thin layer. Microtoming of a paint cross-section embedded in a modern resin was not successful. The various samples were analysed by infrared spectroscopy to assess the usefulness of these sample preparation techniques in the field of paintings research. The amount of information that can be derived from the infrared spectra obtained appeared optimal for sample preparation methods that allow the application of transmission techniques. The results obtained for specular reflectance techniques were of lesser quality, while no diffuse reflectance spectra could be obtained. The results can best be traced to a specific layer or structu...

Peas (Pisum sativum L.) consist mainly of cotyledons and their bulk material is starch and proteins. Their structure is rather confined. Peas were heated at temperatures ranging from 130 to 700 °C under anoxic conditions for maximum 2 h. For each temperature a separate experiment was carried out in a pre-heated oven. Direct temperature-resolved mass spectrometry (DTMS) under electron impact (EI) and chemical ionization (CI, NH3) conditions measured the molecular composition of each solid residue. Fourier-transform infrared (FTIR) spectroscopy was carried out on residues heated at higher temperatures. The resulting solid products of the heating process still show the original markers for polysaccharides and proteins up to 270 °C. Concurrently three phases can be considered, each characterized by its own products. The first phase, from 270 up to 310 °C, shows monosaccharides, protein fragments and aromatic compounds. The second phase, from 310 °C up to a transitional stage from 400 to 440 °C, releases various aromatic and heterocyclic compounds. The third phase at higher temperatures shows a highly C-enriched product that releases CO, CO2, HCN, SO and SO2. The EI and CI experiments fail to discriminate between the pyrolysis products of polysaccharides and proteins between 250 and 400 °C. FTIR shows in this temperature range the development of an aromatic network. An earlier classification based on the changes of the physical and bulk chemical properties as a function of the temperature corresponds well with the classification based on the molecular changes. Residues of heated peas, usually called carbonized peas, are found in the archaeological record. Our study suggests that peas should have been heated up to least 310 °C before their residues survive natural degradation processes.

The residues of heated organic remains, usually called carbonized or charred remains, are ubiquitous in the archaeological record and are often used to interpret certain aspects of past ways of living. This study focuses on the physical and chemical alterations, both as a function of temperature and time that occur when the transformation of a polysaccharide-rich biomass is simulated in the laboratory. Peas (Pisum sativum) are heated at temperatures ranging from 130–700 °C under anoxic conditions and atmospheric pressure, during a maximum of 2 h. Changes in weight and the relative percentages of C, N, H and O are noted alongside modifications of the internal and external morphology. Vitrinite reflectance provides an elegant tool to determine the heating temperature of the residues. The kinetics that determine the changes and modifications are discussed. The resulting solid products of the heating process can be conveniently considered in five phases, which fit the physical and chemical properties. The simulation provides a rigorous basis for the study of the formation processes, as applied in the archaeology, after the so-called “carbonization” process.

Whole grains of emmer wheat were heated in a pre-heated tube oven at temperatures ranging from 130–700°C under controlled anoxic conditions for maximum 280 min. For each temperature a separate experiment was carried out. Physical properties including mass loss, thermal lag, external and internal morphology and the vitrinite reflectance, C and N content, and DTMS under CI (NH3) and EI conditions were used to monitor changes as a function of the temperature. The results show remaining starch and protein rich material up to 250°C. From 310–400°C a secondary, thermally stable, product is formed and at higher temperatures a strongly carbon enriched tertiary product.

Modern and contemporary art collections show an increasing number of paintings with softening oil paints, exudates, and even drips. Since 2013 the condition of the paints on ca. 100 paintings from ...

The photodegradation of indigo has been studied with emphasis on the degradation products. Ultraviolet-visible spectrometry, high performance liquid chromatography and direct temperature-resolved mass spectrometry were employed for the characterisation of aged samples. Indigo, isatin, isatoic anhydride, anthranilic acid and indirubin were detected, together with other unidentified compounds. A new degradation product, tryptanthrin, was identified by both high performance liquid chromatography and mass spectrometry techniques, and two other possible degradation products have also been suggested. The degradation of synthetic and natural indigo has been compared and an explanation for the higher rate of degradation of natural indigo proposed.

Electron impact (EI) ionization and ammonia chemical ionization (NH3/CI) direct-temperature mass spectrometry (DTMS) was used to characterize five natural terpenoid resins: dammar, mastic, colophony, Manila copal and sandarac. Compositional differences were highlighted by the identification of low molecular mass compounds, ranging from di- to triterpenoids, and polymeric components, based on polycadinene and polycommunic acid. Photo-ageing processes occurring under accelerated indoor and outdoor exposure conditions were also investigated. NH3/CI and tetramethylammonium hydroxide EI were applied to increase the sensitivity towards highly oxidized molecules. Oxidation and cross-linking reactions were found to affect mostly triterpenoid resins and diterpenoid abietane and pimarane molecules. Oxidation proceeds through a radical mechanism, generally starting from conjugated double bonds. Oxygen atoms are incorporated in the terpenoid structures in the form of alcohols, ketones and carboxylic acids. Oxidized cadinene oligomers released by pyrolytic degradation of the polycadinene fraction of dammar were detected even in unaged samples. Evidence is given indicating the occurrence of cleavages in the cross-linked polycommunic structure of aged sandarac and Manila copal. Bond scissions produce oligomeric fragments based on the communic acid structure and sufficiently volatile to be desorbed at low temperature in DTMS measurements. Copyright © 2003 John Wiley & Sons, Ltd.

Synthetic polymers are demonstrated to be very useful probes for the characterization of a newly constructed external ion source matrix-assisted laser desorption and ionization quadrupole ion trap mass spectrometer (MALDI-ITMS). Mass discrimination effects and space-charge-induced mass shifts can readily be identified and quantified with these synthetic polymer probes. Mass dependencies in the trapping efficiency were evaluated by comparison of measurements of poly(methyl methacrylate) (PMMA) standards in the mass range m / z 400–3400 with MALDI-TOF-MS measurements of the same samples. This established the optimal experimental conditions for the analysis of mass ranges smaller than 1000 u with negligible mass discrimination. This is demonstrated on the basis of measurements on a tri-block copolymer of poly(ethylene oxide) poly(propylene oxide). As expected, mass measurements were highly influenced by the magnitude of the trapped ion population. Using poly(ethylene glycol) standards we were able to quantify these mass shifts as a function of the total ion load. Consequently, reproducible results can only be obtained by reproducing the total space-charge in the trap. In MALDI experiments, this can be achieved by tuning the laser power just above threshold. This approach allowed the mass determination of three different end groups in a complex Jeffamine D2000 sample with an accuracy of better than 0.1 u.

Charred organic remains are ubiquitous in the archaeological and fossil record and are often used to interpret past environments and climate. This study focuses on the physical and chemical alteration that takes place during heating (i.e. charring). Modifications to the internal and external morphology were noted alongside the change in molecular and stable carbon isotope signature. Molecular analyses were undertaken using direct temperature resolved mass spectrometry and the stable carbon isotopes determined using isotope ratio mass spectrometry. The results of this study document a general enrichment in 13 C/ 12 C composition of charred material which could reflect the changes observed in both the molecular composition and the relative proportions of the molecules formed. These results indicate that spurious results might be inferred when comparing the stable carbon isotope signature of charred/charcoalified material with uncharred organic matter

Direct temperature resolved mass spectrometry (MS) is a microanalytical technique to analyse modern paints by thermal separation and ionisation of organic pigments and polymeric fractions from a platinum/rhodium filament inside the ionisation chamber of the mass spectrometer. Most organic pigments in modern paints are desorbed at lower temperatures. Ethyl acrylate/methylmethacrylate or butyl acrylate/methylmethacrylate copolymers used in acrylic emulsion paints produce mono and oligomeric subunits released from the copolymers at high temperature by pyrolysis. Characteristic low voltage electron ionisation and ammonia chemical ionisation (CI) mass spectra of these copolymers facilitate their identification. DTMS of three different commercial acrylic emulsion paints showed low and high temperature events that could be related to the presence of organic pigments and the acrylic copolymers. Polyethylene glycols with molecular weight up to 2000 Da were identified as additives under ammonia CI conditions. The azo pigments PY3, PY73 and PY74, and the phthalocyanine pigment PG7 reported show molecular ions and a few characteristic fragment ions under direct temperature resolved mass spectrometry (DTMS) analytical conditions. Yellow azo pigments were identified under DTMSMS conditions by their high energy collisionally induced fragment patterns of their parent ions. Laser desorption ionisation mass spectrometry (LDIMS) using a nitrogen laser (337 nm) of an acrylic emulsion paint with four different organic pigments produced radical cations, protonated or sodiated ions of the pigments. The amide bond in the azo pigment PY3 was photolytically cleaved and produced a specific fragment ion. The trace additive polyethylene glycol was observed preferentially while the acrylic copolymers were transparent.

High performance size-exclusion chromatography (HPSEC) and direct temperature-resolved mass spectrometry (DT-MS) were used to explore molecular weight distributions and molecular level characteristics within marine/estuarine ultrafiltered dissolved organic matter (UDOM, >1 kDa) collected from the lower Chesapeake Bay, USA and the Oosterschelde estuary, The Netherlands. Initial HPSEC characterization indicates that the overall size distribution is similar in all the UDOM samples; however, there are distinct variations among the samples, especially in the low molecular weight region. As a preliminary study of molecular level variations with apparent molecular size, the Oosterschelde UDOM sample was separated into molecular weight fractions using HPSEC. These fractions were then analyzed by DT-MS. The size fractions within the UDOM sample yielded distinctly different mass spectra; the larger size classes were enriched in aminosugars, deoxysugars, and methylated sugars while the smaller size classes were enriched in hexose sugars. There is also evidence that hexose sugars appear in at least two structures with highly different molecular weights and potentially highly different source and sink functions within the marine water column.

Fourier transform infrared imaging is presented as a new analytical approach in the study of paint cross-sections. Analytical FT-IR reflection imaging provides the spatially resolved acquisition of infrared spectra with a resolution of about 7 μm. The technique reveals detailed information on the organic functional group distribution in the individual layers of embedded paint cross-sections and is used complementary to visual microscopy and scanning electron microscopy/energy dispersed X-ray spectroscopy (SEM-EDX). This method was applied to a paint cross-section of Rembrandt's Portrait of a Standing Man (1639). FT-IR imaging of this cross-section identified and localized different compounds present in the layers of this sample. Identification of these compounds based on their infrared spectra is confirmed by results from art historical and conservation literature. Special attention was given to a discoloration that was observed in large parts of the described painting. This discoloration was clearly visible in the paint cross-section. A hypothesis on the nature of the discolored paint layer is formulated based on the FT-IR imaging results.

Asphalt has been used since antiquity for various purposes and by painters since the 17th century. Asphalt as a pigment material with a known pre-19th century provenance is extremely rare. The analytical pyrolysis techniques of direct temperature-resolved mass spectrometry (DTMS) and pyrolysis gas liquid chromatography coupled with mass spectrometry (Py-GC/MS) were applied to characterise a unique ‘asphalt’ sample from a painting materials collection dating from the early 19th century. The provenance of this sample was investigated by comparison with a sample from a present day floating asphalt from the Dead Sea. DTMS demonstrated a complex envelope of ions from hydrocarbons ranging past m/z 1000 in both samples. Both samples showed evaporating sets of compounds as well as pyrolysing materials evolving from asphaltenes. Asphaltene network polymers were marked by aliphatic cross-links releasing alkenes and alkanes, and aromatic centres releasing alkylbenzenes, alkylnaphthalenes, alkylanthracenes, alkylphenanthrenes, and alkylbenzothiophenes. Hopanoid hydrocarbons and C-ring monoaromatic steroid hydrocarbons were among the biomarker compounds identified. Particularly striking were homologous series of alkylbenzothiophenes and alkyldibenzothiophenes with long hydrocarbon chains that could be traced with DTMS and confirmed by DTMS/MS. The results indicate that the early 19th century ‘asphalt’ sample from the Hafkenscheid collection is indeed a true asphalt that shows many similarities to the Dead Sea asphalt sample, which is therefore proposed as the possible region of provenance.

Two approaches are introduced that provide information about the isomeric composition of hyperbranched polyesteramides. The first approach is based on a novel tandem mass spectrometric (MSn) approach that allows the study of different types of isomeric structures by a separation based on their difference in appearance energy. The method is called DoDIP: dissociation of depleted ion populations. A first MS/MS step is used to fragment isomers with relatively low appearance energy. The isomers with higher appearance energy are fragmented in a second MS/MS step of higher energy. The second approach is based on gas-phase H/D exchange experiments that result in a bimodal isotopic distribution for oligomers XnDn+1 of which one distribution corresponds to a type of isomeric structure that exhibits H/D exchange behaviour and the other to an isomeric structure that does not exhibit H/D exchange behaviour. X is a difunctional anhydride of phthalic acid (P), 1,2-cyclohexanedicarboxylic acid (C), succinic acid (S) or glutaric acid (G). D in XnDn+1 is a trifunctional diisopropanolamine and n the degree of polymerization. The type of isomeric structure that does not exhibit H/D exchange behaviour has a non-alternating monomer sequence that contains an amine bond with a relatively high proton affinity. The other isomeric structure that does exhibit H/D exchange behaviour has an alternating monomer sequence containing only amide and ester bonds with relatively low proton affinity. Oligomer structures were confirmed with additional MS2 experiments after H/D exchange. H/D exchange experiments on the fragments obtained after MS2 of the parent ion show that next to previously postulated mechanisms for the cleavage of the ester and amide bond another reaction pathway must be operational. A new mechanism is introduced to explain the H/D exchange behaviour of the fragments that requires a cleavage of the amide bonds only. Two types of fragments are formed by this mechanism. One type is protonated due to the cleavage of the amide bond whereas the other type has an oxazolonium ion structure due to the loss of an additional H2O. Copyright © 2002 John Wiley & Sons, Ltd.

The painting Composition (1952) by Jean Paul Riopelle (1923–2002) is part of the Henie Onstad Art Centre’s collection in Norway. Examination of the painting revealed the presence of drips of soft medium exuding from the surface. The main aim of this paper is to report chemical characteristics of its hard, soft and dripping paints. Information was collected about Riopelle’s use of materials. Data were obtained from microsamples by analysis with Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM-EDX) and Direct Temperature resolved Mass Spectrometry (DTMS). Composition (1952) is painted with 26 different colours or shades of paint. All these paints vary in their specific physical condition when tested on the painting. Paints were classified into three categories: hard, soft, softer and dripping. The most problematic of all paints contained cobalt blue pigment.

A painting from the Seven series by Frank van Hemert made between 1990 and 1995 was starting to show fluorescent exudates and drips after about 7 years. Paint samples were investigated with analytical mass spectrometry, solid state NMR, imaging FTIR and SEM-EDX. Fluorescent exudate of fluidised paint compared to rubbery paint underneath showed differences in FTIR and MS characteristics related to the distribution of polar acylglycerides with ester bonded and free azelaic acid groups. The oil in the Schmincke Norma Fleischfarbe nr 213 tube paint used by van Hemert consists mainly of semidrying oil giving a Drying Index of 72. Imaging FTIR identified aluminium soaps in fluorescent vesicles in the solid rubbery paint. Solid state NMR indicated that these aluminium soaps are degraded and consist mainly of aluminium hydroxy-monostearates. DTMS and ESIMS showed apolarity inside the rubbery paint compared to the exuding material. The drying of the paint produced high relative amounts of smaller oxidised fractions that could not be retained in the paint mass as aging progressed. A physical separation resulted in more polar fractions. The fluorescence of these exuding fractions can be used a tracer for failing or impending failing of oil paint.

The Menaced Assassin by Rene Magritte is a major surrealist painting from the collection of the Museum of Modern Art (MoMA). A recent conservation treatment coupled with scientific analysis has characterised some puzzling and visually disturbing surface phenomena once attributed to mold growth.

The formation of α-methylated and α,α-dimethylated (di)acids during on-line (trans)methylation with tetramethylammonium hydroxide (TMAH) in a Curie-point pyrolysis unit is studied. The reaction of TMAH with nonanedioic, hexadecanedioic and octadecanoic acids is investigated to determine the contribution of the solvent system and the amount of TMAH added to this phenomenon. The results obtained clearly show a different behaviour of diacids in methanolic solutions compared to aqueous systems. At least three different reaction products were identified for the acids when using a methanolic solution of TMAH. Different relative amounts of by-products were formed when varying the amount of TMAH reagent relative to the normal methylated reaction product. A mechanism is postulated for their formation and a hypothesis is drawn up to explain the observed differences in reactivity for both solvents.

Estuarine modification of terrestrial and riverine/estuarine organic matter may strongly affect the eventual preservation of reduced carbon in world oceans and is also important in nutrient and contaminant cycling. In this study multiple size classes of organic matter (including particles and dissolved fractions, POM and DOM) from a transect down the Delaware River/Bay system were collected and analyzed. Variations in chemical characteristics were identified using direct temperature-resolved mass spectrometry (DT-MS) and wet chemical techniques coupled with discriminant analysis and canonical correlations analysis. These comparative measures illustrate the complementary nature of traditional versus more recent mass spectrometry approaches. Within the estuary system, organic matter size class, rather than sample location, is found to be the major source of molecular-level variation. POM is enriched in proteins, nucleic acids, fatty acids, chlorophyll, and sterols, whereas DOM is enriched in aminosugar, furfural, and alkylphenol moieties. In positive ammonia chemical ionization DT-MS studies, which focus on the sugar components in POM and DOM, riverine very high molecular weight DOM (>30 kDa

Four hyperbranched synthetic polyesteramides were synthesized by the polycondensation of the trifunctional diisopropanolamine (D) and difunctional anhydrides (X) of succinic acid, glutaric acid, 1,2-cyclohexane dicarboxylic acid, and phthalic acid. The polymers were analyzed with electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The most intense oligomer series observed was XnDn+1 containing diisopropanolamine end groups as expected from the polycondensation conditions. A series of oligomers XnDn+1H2O is observed as well, which can have its origin in the polymerization process or alternatively could result from in-source fragmentation of XnDn+1. Breakdown diagrams of the protonated parent ions X3D4 and additional MSn (n = 1, 2, 3) measurements gave insight in the fragmentation behavior of the polymers. Three main fragmentation pathways have been observed for all polymers of which the loss of H2O to oxazolonium ions has the lowest onset energy followed by the rearrangement of the amide and ester bonds also leading to oxazolonium ions. The loss of a second H2O to allylic or morpholine end groups has highest onset energy. MS3 experiments demonstrated that the presence of a series of oligomers XnDn+1H2O can be attributed to the polymerization process. Most probably an allylic end group has formed from one of the alcohol end groups. The formation of allylic end groups partly terminates the polymerization reaction and results in a change of the composition of the molecular weight distribution and decrease of the number average molecular weight.

An elegant method is described for the determination of the degree of hydrolysis of (unsaturated) triacylglycerols, and their oxidation products, present in linseed oil based paints. The analytical strategy, a transethylation of esterified fatty acids followed by a trimethylsilylation of free fatty acids and their salts, is first tested on reference materials comparable or identical to the compounds present in fresh and aged oil paints. Reproducibility and repeatability are examined on free- and methylated fatty acids, a sodium- and lead salt and several triacylglycerols. Unwanted trimethylsilylated products could be observed for the triacylglycerols and other esterified fatty acids up to a maximum of 6%. Free fatty acids and their salts are shown to be completely trimethylsilylated but incomplete derivatisation was observed for azelaic acid. Glycerol, liberated upon transethylation was (partially) trimethylsilylated. However, the recovery was not uniform and the results could not be used for quantitative determination of the amount glycerol in the paint sample. Studies on the influence of the pigments indigo, lead white, and prussian blue and glycerol showed there is no adverse influence on the analytic result, except for lead white and indigo doped reference material. The addition of these last compounds led to increased amounts of hydrolysed products up to 37%. The repeatability of the determination of the degree of hydrolysis within oil paint systems was tested on a number of paints. It is shown for 5-year-old test paints with a relatively homogeneous composition that the method is reproducible. For less defined paints consisting of multi-layered systems it is shown that the position and way of sampling can have a significant influence on the spread in the analytical result. This is caused by the large variations that are possible in the sampled material in these inhomogeneous systems. The degree of hydrolysis of an oil paint is taken as the average of the values obtained for azelaic-, palmitic- and stearic acid, based on the results presented. Overall, it is observed that the relative amount of hydrolysed fatty (di)acids increases in time. Surprisingly, in contrast to the results obtained on reference material, for all lead white pigmented paints lower degrees of hydrolysis were found relative to other paints from that particular set.

An extremely low level of the cinnamyl alcohol dehydrogenase (CAD) enzyme activity in a mutant loblolly pine tree leads to a different pool of precursors for lignin production. Characterization of CAD-deficient wood by pyrolysis mass spectroscopy indicates significant increased levels of dihydroconiferyl alcohol, not usually considered a lignin subunit. Also, in comparison to normal pine lignin, the CAD-deficient lignin has increased levels of coniferaldehyde, the substrate of CAD, and of p-coumaryl alcohol, along with greatly decreased levels of coniferyl alcohol. These findings are consistent with trees of different ages and confirm that there is considerable plasticity in the biosynthesis of lignin. Trees are able to utilize structures beyond the traditional definition of precursors to make lignin.

Oxidative changes in triacylglycerols and diacylphosphatidylcholines in egg tempera paint strips are used for chemical dosimetry of the quality of the museum environment. High-resolution matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS) was used as a rapid method for the determination of the exact elemental composition of the alteration products from diacylphosphatidylcholines and triacylglycerols. Light exposure of the egg tempera paints yields oxygenated diacylphosphatidylcholines and triacylglycerols. In the latter multiple incorporation of oxygen was observed as a recurring mass difference of 15.995, the exact atomic mass of oxygen. Owing to the high resolution of the FTMS data (routinely 20 000 at m/z 1000 in broadband mode), oxidation products with different elemental compositions but identical nominal mass could be distinguished. Products of oxidative cleavage of triacylglycerols were observed in samples exposed for longer times. The relative intensities of the peaks of singly and multiply oxygenated triacylglycerols were used to derive the degree of oxygenation of the egg lipids in the tempera paint dosimeters. The degree of oxygenation was found to be directly related to the light exposure time. Exposure to elevated temperature (60 °C) for a period of 21 days did not lead to oxygenation of the triacylglycerols and diacylphosphatidylcholines. Exposure to NOx and SO2 in the dark greatly increased the degree of oxygenation. Addition of lead- or copper-containing pigments to the egg binding medium (and subsequent storage for 6 months in the dark) led to accelerated conversion of egg lipids to oxidised products. Copyright © 2001 John Wiley & Sons, Ltd.

The chemical composition of suberin in cork from Quercus suber L. was determined on virgin and reproduction cork from different sites and trees in Portugal. Extractive-free samples were analyzed by pyrolysis-gas chromatography/mass spectrometry in the presence of tetramethylammonium hydroxide (TMAH), which provides in situ hydrolysis and (trans)methylation of hydroxyl and carboxyl groups of the suberin monomers. The average chemical monomeric composition of suberin on virgin and reproduction cork is, respectively, alkanoic acids 5.1, 3.3%; α,ω-diacids 11.2, 10.1%; ω-hydroxyacids 45.0, 48.1%; alkanols 1.9, 1.8%; 9,10-epoxy-18-hydroxyoctadecanoic acid 5.9, 5.8%; 9,10-epoxyoctadecanodioic acid 4.8, 3.6%; 9,10,18-trihydroxyoctadecanoic acid 7.5, 10.4%; 9,10-dihydroxyoctadecanedioic 6.1, 6.8%; ferulic acid 5.8, 4.5% and glycerol 4.3, 4.3%. In general, larger variability was found for the suberin monomers in virgin cork. Total content of ω-hydroxyacids or of C18 or C22 compounds is however similar for all samples.

Despite recent progress, several aspects of lignin biosynthesis, including variation in lignin composition between species and between tissues within a given species, are still poorly understood. The analysis of mutants affected in cell wall biosynthesis may help increase the understanding of these processes. We have analyzed the maize brown midrib2 (bm2) mutant, one of the four bm mutants of maize, using pyrolysis-mass spectrometry (Py-MS) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). Vascular tissues from the leaf blade and leaf sheath from different parts of the plant were investigated and compared to the corresponding samples from a wild-type plant of the same genetic background (inbred line A619). Multivariate analysis revealed that the bm2 mutant had reduced amounts of di- and trimeric lignin derivatives, notably species with m/z 272 and m/z 330, and that the ratio of guaiacyl residues to polysaccharides was reduced in the bm2 mutant. In addition, differences in cell wall composition between different parts of the plant (blade versus sheath, young versus old tissue) were much less pronounced in the bm2 mutant. These changes suggest that the functional Bm2 gene is important for the establishment of tissue-specific cell wall composition.