Direct chemolysis–gas chromatography–mass spectrometry for analysis of paint materials (original) (raw)
Related papers
Gas chromatography/mass spectrometry of oils and oil binders in paintings
Journal of Separation Science, 2008
Gas chromatography/mass spectrometry of oils and oil binders in paintings A GC/MS procedure has been developed, optimized, and applied to characterization of oil binders in paintings. The procedure involves hydrolysis of lipids to fatty acids (FAs) and derivatization of FAs to fatty acid methyl esters (FAMEs) by a solution of sodium methanolate in methanol at an elevated temperature. FAMEs are analyzed by temperature-programed GC followed by full-scan MS. Old and dried samples are subjected to extraction of nonpolymerized FAMEs into dichloromethane prior to hydrolysis. The method provides a good repeatability of results and has been applied to the characterization of common plant oils used in paintings, to commercial oil and tempera paints, to model painting samples, and to samples taken from real paintings. The fresh oils and binders can readily be identified and characterized. The ratio of the methyl esters of palmitic and stearic acids can be used to characterize oil binders in old works of art.
Journal of Analytical and Applied Pyrolysis, 2002
Conservation scientists are frequently asked to identify the materials that are contained in microscopic fragments from works of art. For decades, the only technique successfully used for characterising the type of oil binder used from dried oil paints has been gas chromatography/mass spectrometry (GCMS). Unfortunately, the process requires a lengthy sample preparation and some of the derivatisation processes used present serious health and safety implications. Although thermally assisted hydrolysis and methylation-GCMS (THM-GCMS) has been used more recently for the analysis of traditional paint binders, its ability to distinguish between different oil types has yet to be ascertained. This paper describes the use of THM-GCMS to examine differences in the fatty acid composition of dried pigmented films of linseed, linseed stand, poppy, safflower and walnut oil. The results were compared for pyrolysis at 610 and 770°C, two of the most commonly used temperatures in Curie point pyrolysis, in order to verify reproducibility of the results. Based on three runs for each sample, the fatty acid composition (measured as methyl esters) was found to be temperaturedependent, as previously suggested in literature. At the lower pyrolysis temperature (610°C), a higher degree of reproducibility was seen and the ability to differentiate between each of the dried oil types using palmitate/stearate (P/S) ratios was improved. Interestingly, the P/S observed for each oil at this pyrolysis temperature were found to be close to those obtained by published GCMS procedures. In addition, samples of dried pigmented films of egg yolk were investigated and it was confirmed that this medium could be differentiated from each : S 0 1 6 5 -2 3 7 0 ( 0 1 ) 0 0 1 6 4 -4 340 F. Cappitelli et al. / J. Anal. Appl. Pyrolysis 63 (2002) 339-348 of the drying oils at this pyrolysis temperature from their azelate/palmitate ratios. These preliminary findings are encouraging for the use of THM-GCMS as an alternative method to GCMS for the identification of oils used as binders in paints.
Analytical Chemistry, 2006
A novel GC/MS analytical procedure for the identification of lipids, waxes, proteins, and resinous materials in the same microsample from painted works of art has been optimized. It is based on a sample multistep chemical pretreatment (solvent extractions and microwave-assisted chemolysis) that is able to separate the various organic components into different fractions, which are suitably treated and derivatized before analysis. In particular, the procedure allows the complete saponification of wax esters and the completeness of the Cannizzaro type reaction of shellac acids in conditions that are suitable also for glycerides saponification. The method was tested on reference materials for the identification of proteinaceous binders (egg, collagen, casein) on the basis of the quantitative determination of the amino acid profile and the identification of glycerolipids (linseed oil, poppy seed oil, walnut oil, and egg), plant resins (Pinaceae resins, sandarac, mastic, and dammar), animal resins (shellac), tars or pitches, and natural waxes (beeswax, carnauba wax) on the basis of the determination of fatty acid, alcohol, and hydrocarbon profiles and of significant terpenic molecular markers. The procedure was applied to the characterization of three old paint microsamples. Animal glue, egg, linseed oil, beeswax, Pinaceae resin, dammar, and shellac were the identified materials found in mixtures and recognized as original and/or restoration substances.
Journal of Chromatography a, 2009
This paper presents a GC-MS analytical procedure for determining proteinaceous materials, glycerolipids, natural waxes and terpenoid resins in the same paint micro-sample. The procedure is also reliable when high amounts of interfering inorganic pigments, dryers and charges are present. The characterisation of proteinaceous binders in a paint sample can be subject to analytical interferences by inorganic materials. Such materials may form complexes with functional groups of proteins, thus preventing their efficient derivatisation, which is necessary prior to GC analysis. For this reason an analytical procedure has been developed based on two extractions and a clean-up step, in order to obtain two fractions: a lipid-resinous fraction and a proteinaceous fraction. The lipid-resinous fraction is subjected to salification/saponification assisted by microwaves, followed by acidification, extraction, derivatisation and GC-MS analysis. The proteinaceous fraction is analysed by GC-MS after hydrolysis and derivatisation of the freed amino acids. The desalting step is applied before the hydrolysis, and is based on the use of the monolithic sorbent tip technology with a C4 stationary phase. Reference paint replicas of egg, casein and animal glue were prepared with and without several metals containing pigments, and used to develop and validate the analytical procedure. The procedure proved to be efficient in desalting the proteinaceous materials both from cations and anions. Although non quantitative, it is reliable in the analysis of samples whose content of extractable proteins is <1 g, thus showing it to be suitable for the characterisation of paint samples. An example of how the analytical procedure was used to characterise a sample from a 15th century panel painting is also discussed.
Analytical and Bioanalytical Chemistry, 2011
A matrix-assisted laser desorption ionization time-of-flight mass spectrometry-based approach was applied for the detection of various lipid classes, such as triacylglycerols (TAGs) and phospholipids (PLs), and their oxidation by-products in extracts of small (50-100 μg) samples obtained from painted artworks. Ageing of test specimens under various conditions, including the presence of different pigments, was preliminarily investigated. During ageing, the TAGs and PLs content decreased, whereas the amount of diglycerides, short-chain oxidative products arising from TAGs and PLs, and oxidized TAGs and PLs components increased. The examination of a series of model paint samples gave a clear indication that specific ions produced by oxidative cleavage of PLs and/or TAGs may be used as markers for egg and drying oil-based binders. Their elemental composition and hypothetical structure are also tentatively proposed. Moreover, the simultaneous presence of egg and oil binders can be easily and unambiguously ascertained through the simultaneous occurrence of the relevant specific markers. The potential of the proposed approach was demonstrated for the first time by the analysis of real samples from a polyptych of Bartolomeo Vivarini (fifteenth century) and a "French school" canvas painting (seventeenth century).
Talanta, 2011
The correct identification of drying oils plays an essential role in providing an understanding of the conservation and deterioration of artistic materials in works of art. To this end, this work proposes the use of peak area ratios from fatty acids after ensuring that the linear responses of the detector are tested. A GC-MS method, previously reported in the literature, was revisited to its developed and validated in order to identify and quantify of eight fatty acids that are widely used as markers for drying oils in paintings, namely myristic acid (C 14:0), palmitic acid (C 16:0), stearic acid (C 18:0), oleic acid (C 18:1), linoleic acid (C 18:2), suberic acid (2C 8), azelaic acid, (2C 9) and sebacic acid (2C 10). The quaternary ammonium reagent m-(trifluoromethyl)phenyltrimethylammonium hydroxide (TMTFAH) was used for derivatization prior to GC-MS analysis of the oils. MS spectra were obtained for each methyl ester derivative of the fatty acids and the characteristic fragments were identified. The method was validated in terms of calibration functions, detection and quantification limits and reproducibility using the signal recorded in SIR mode, since two of the methyl derivatives were not totally separated in the chromatographic run. The proposed method was successfully applied to identify and characterise the most widely used drying oils (linseed oil, poppy seed oil and walnut oil) in the painting La Encarnación. This 17th century easel painting is located in the main chapel of the cathedral in Granada (Spain) and was painted by the well-known artist of the Spanish Golden Age, Alonso Cano (1601-1667).
Comparison of oil and egg tempera paint systems using Time-of-Flight Secondary Ion Mass Spectrometry
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is quickly becoming a critical tool in the field of art conservation. This technique provides high-resolution spatial maps of both inorganic and organic components located within cross-sectional samples collected from works of art. With recent advances in surface analysis, ToF-SIMS can now be used to identify specific amino acids present in protein-containing materials as well as fatty acids in drying oils. For example, the detection of the ion fragment associated with the amino acid hydroxyproline can be used to confirm the use of animal glue in a paint sample. As an analytical technique, ToF-SIMS avoids the need for derivatization/silylation reagents, with no interference by the presence of pigments. Furthermore, the layered systems that are often encountered in historical paint samples remain intact throughout the analytical procedure. This allows for the colocalization of organic and inorganic species in specific layers (e.g. egg yolk paint atop a glue ground). Because of this ability to localize the analytical signal to approximately 6 μm or less, the mass spectral information can be used to produce mass-resolved and spatially-resolve images which can be correlated to previous studies of the same samples. In this study, ToF-SIMS was used to analyze a paint cross section obtained from a painting attributed to Raphael, and another from a painting by the Sienese artist Matteo di Giovanni.
Accounts of Chemical Research, 2010
T hroughout history, artists have experimented with a variety of organic-based natural materials, using them as paint binders, varnishes, and ingredients for mordants in gildings. Artists often use many layers of paint to produce particular effects. How we see a painting is thus the final result of how this complex, highly heterogeneous, multimaterial, and multilayered structure interacts with light.
Journal of Chromatography A, 2005
A HPLC-fluorescence 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. Fluorescence derivatization of fatty acids released by hydrolysis of structural drying oils is studied. The derivatization reagent was 4-(bromomethyl)-7-methoxycoumarin with 18-crown-6 as catalyst. Mobile phase was programmed from methanol-water (90:10 v/v) to methanol-water (100:0 v/v) in 25 min. The excitation and emission wavelengths were 325 and 395 nm, respectively. Under these chromatographic conditions, coumarin derivatives of myristic, palmitic, oleic and stearic acids were satisfactorily resolved. The method shows good sensitivity, with a detection limit of 6.0 × 10 −8 mmol, and good linearity between 1.0 × 10 −7 and 1.8 × 10 −4 mmol of each analyte. Peak area ratios among fatty acids derivatives, especially the stearic acid/palmitic acid peak area ratio, are useful to identify the drying oils. The proposed method has been successfully applied to artistic samples from items of the cultural heritage of Valencia (Spain).