Model study of modern oil-based paint media by triacylglycerols profiling in positive and negative ionization modes

Lipid binders have traditionally been determined in paintings by using gas chromatography/mass spectrometry (GC/MS) to identify the characteristic profiles and ratios of fatty acids . However, the presence of mixtures in contemporary and modern oil paints makes the GC/MS determination of fatty acids insufficient to fully characterize the lipid binding media. In this study we prove that triacylglycerol (TAG) profiling by high-performance liquid chromatography with high-resolution tandem mass spectrometry, using ESI in positive and negative ionization modes is highly effective. We exploited this analytical approach to study the curing and degradation processes undergone by six plant oils used in the formulation of media in modern paints, using both natural and artificial ageing experiments. We believe that is the first time that a negative ionization mode has been applied for this purpose and that a survey with HPLC-ESI-Q-ToF has been carried out to study the ageing kinetics of plant oils. TAG profiling enabled us to study the evolution over time of the constituents of modern oils, with respect to curing and ageing. The data analyzed in this study demonstrate that our approach is efficient to study the oxidation of TAGs during ageing. The data also improve current knowledge on the properties of vegetable oils, which could lead to the development of new paint materials and conservation treatments for modern and contemporary works of art

Synthetic materials in art: a new comprehensive approach for the characterization of multi-material artworks by analytical pyrolysis

Abstract Modern art materials introduced since the end of XIX century include a large number of formulations of synthetic polymers and pigments, whose degradation processes and best preservation conditions are a major issue in heritage science. Analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) is widely used for the characterisation of polymeric materials and organic pigments, however the interpretation of the pyrograms obtained from samples containing different analytes is not straightforward. To improve our understanding on how these materials behave in complex matrices, we used evolved gas analysis coupled with mass spectrometry (EGA-MS) and multi shot Py-GC/MS to highlight and analyse the different fractions in a sample from a pop-art made of painted polyurethane (PU) foam. The study represents a proof of concept to evaluate EGA-MS potential in studying composite modern art materials in combination with multi-shot pyrolysis. The aim of the investigation was establishing the composition of the PU formulation, the paint binder and the pigments, thereby contributing to planning the stabilisation and conservation of the object. The polymers and the class of synthetic organic pigments present in the paint were assessed by determining their specific pyrolysis products and through comparisons with data in the literature. EGA-MS analysis provided both thermal and chemical information in one analytical run, so that we could select four temperatures for use in multi-shot Py-GC/MS analysis and thus to selectively study the different fractions evolved at different temperatures. Information on the various components of the mixture was obtained, including additives and organic pigments, separating them on the basis of their different thermal degradation temperatures. The multianalytical approach included also non-destructive ATR-FTIR and enabled us to characterize in detail different synthetic materials: polyether-based polyurethane produced by the polyaddition of 2,6-diisocyanate toluene, hexamethylene diisocyanate and polypropylene glycol, vinyl paint, and a mixture of β-naphthol and mono-azo as pigments. HPLC–DAD and HPLC–ESI–MS analyses confirmed the pigments, and provided a positive identification of two β-naphthols (PO5 and PR1) and two monoazo pigments (PY1 and PY3)

A Systematic Study on the Degradation Products Generated from Artificially Aged Microplastics

Most of the analytical studies focused on microplastics (MPs) are based on the detection and identification of the polymers constituting the particles. On the other hand, plastic debris in the environment undergoes chemical and physical degradation processes leading not only to mechanical but also to molecular fragmentation quickly resulting in the formation of leachable, soluble and/or volatile degradation products that are released in the environment. We performed the analysis of reference MPs–polymer micropowders obtained by grinding a set of five polymer types down to final size in the 857–509 μm range, namely high‐ and low‐density polyethylene, polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET). The reference MPs were artificially aged in a solar‐box to investigate their degradation processes by characterizing the aged (photo‐oxidized) MPs and their low molecular weight and/or highly oxidized fraction. For this purpose, the artificially aged MPs were subjected to extraction in polar organic solvents, targeting selective recovery of the low molecular weight fractions generated during the artificial aging. Analysis of the extractable fractions and of the residues was carried out by a multi‐technique approach combining evolved gas analysis–mass spectrometry (EGA–MS), pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS), and size exclusion chromatography (SEC). The results provided information on the degradation products formed during accelerated aging. Up to 18 wt% of extractable, low molecular weight fraction was recovered from the photo‐aged MPs, depending on the polymer type. The photo‐degradation products of polyolefins (PE and PP) included a wide range of long chain alcohols, aldehydes, ketones, carboxylic acids, and hydroxy acids, as detected in the soluble fractions of aged samples. SEC analyses also showed a marked decrease in the average molecular weight of PP polymer chains, whereas cross‐linking was observed in the case of PS. The most abundant low molecular weight photo‐degradation products of PS were benzoic acid and 1,4‐benzenedicarboxylic acid, while PET had the highest stability towards aging, as indicated by the modest generation of low molecular weight species

Scientific investigation into the water sensitivity of twentieth century oil paints

In order to develop a better understanding at the molecular level of water sensitivity in twentieth century oil paintings, water sensitive Winsor & Newton oil paint swatches and twentieth century oil paintings were characterised using gas chromatography–mass spectrometry (GC–MS) and direct injection electrospray ionisation mass spectrometry (ESI-MS), and the data were analysed using principal component analysis. Liquid chromatography coupled with tandem mass spectrometry based on quadrupole and time of flight mass detectors and electrospray interface (HPLC-ESI-Q-ToF) was also used to obtain a better insight into the molecular composition of a selection of samples. The study highlights a strong relationship between the molecular composition of the binding medium and the type of pigment present in the paint, which relates to water sensitivity. Consistently non-water sensitive lead white, titanium white, and zinc white paints [all containing zinc oxide] contained a relatively low proportion of extractable diacids, and a relatively high proportion of extractable short chain monoacids. These paints also contained a relatively low level of unsaturated and hydroxylated glycerides. Water sensitive iron oxide and ultramarine paints are associated with both a relatively high degree of oxidation and a high proportion of extractable diacids, as well as a relatively high content of unsaturated and hydroxylated glycerides. Water sensitive cadmium red, yellow and orange paints were generally not highly oxidised, but they also contained a relatively high content of unsaturated and hydroxylated glycerides. It is hypothesised that water sensitivity relates to a low degree of saponification and crosslinking and possibly, on the relative content of dicarboxylic acids

Microplastic pollution in the sediments of interconnected lakebed, seabed, and seashore aquatic environments: polymer-specific total mass through the multianalytical “PISA” procedure

The total mass of individual synthetic polymers present as microplastic (MP < 2 mm) pollutants in the sediments of interconnected aquatic environments was determined adopting the Polymer Identification and Specific Analysis (PISA) procedure. The investigated area includes a coastal lakebed (Massaciuccoli), a coastal seabed (Serchio River estuarine), and a sandy beach (Lecciona), all within a natural park area in Tuscany (Italy). Polyolefins, poly(styrene) (PS), poly(vinyl chloride) (PVC), polycarbonate (PC), poly(ethylene terephthalate) (PET), and the polyamides poly(caprolactame) (Nylon 6) and poly(hexamethylene adipamide) (Nylon 6,6) were fractionated and quantified through a sequence of selective solvent extractions followed by either analytical pyrolysis or reversed-phase HPLC analysis of the products of hydrolytic depolymerizations under acidic and alkaline conditions. The highest concentrations of polyolefins (highly degraded, up to 864 μg/kg of dry sediment) and PS (up to 1138 μg/kg) MPs were found in the beach dune sector, where larger plastic debris are not removed by the cyclic swash action and are thus prone to further aging and fragmentation. Surprisingly, low concentrations of less degraded polyolefins (around 30 μg/kg) were found throughout the transect zones of the beach. Positive correlation was found between polar polymers (PVC, PC) and phthalates, most likely absorbed from polluted environments. PET and nylons above their respective LOQ values were found in the lakebed and estuarine seabed hot spots. The pollution levels suggest a significant contribution from riverine and canalized surface waters collecting urban (treated) wastewaters and waters from Serchio River and the much larger Arno River aquifers, characterized by a high anthropogenic pressur

Polymer Identification and Specific Analysis (PISA) of Microplastic Total Mass in Sediments of the Protected Marine Area of the Meloria Shoals

Microplastics (MPs) quantification in benthic marine sediments is typically performed by time-consuming and moderately accurate mechanical separation and microscopy detection. In this paper, we describe the results of our innovative Polymer Identification and Specific Analysis (PISA) of microplastic total mass, previously tested on either less complex sandy beach sediment or less demanding (because of the high MPs content) wastewater treatment plant sludges, applied to the analysis of benthic sediments from a sublittoral area north-west of Leghorn (Tuscany, Italy). Samples were collected from two shallow sites characterized by coarse debris in a mixed seabed of Posidonia oceanica, and by a very fine silty-organogenic sediment, respectively. After sieving at <2 mm the sediment was sequentially extracted with selective organic solvents and the two polymer classes polystyrene (PS) and polyolefins (PE and PP) were quantified by pyrolysis-gas chromatography-mass spectrometry (Pyr-GC/MS). A contamination in the 8–65 ppm range by PS could be accurately detected. Acid hydrolysis on the extracted residue to achieve total depolymerization of all natural and synthetic polyamides, tagging of all aminated species in the hydrolysate with a fluorophore, and reversed-phase high performance liquid chromatography (HPLC) (RP-HPLC) analysis, allowed the quantification within the 137–1523 ppm range of the individual mass of contaminating nylon 6 and nylon 6,6, based on the detected amounts of the respective monomeric amines 6-aminohexanoic acid (AHA) and hexamethylenediamine (HMDA). Finally, alkaline hydrolysis of the residue from acid hydrolysis followed by RP-HPLC analysis of the purified hydrolysate showed contamination by polyethylene terephthalate (PET) in the 12.1–2.7 ppm range, based on the content of its comonomer, terephthalic acid

Plastic breeze: Volatile organic compounds (VOCs) emitted by degrading macro- and microplastics analyzed by selected ion flow-tube mass spectrometry

Pollution from microplastics (MPs) has become one of the most relevant topics in environmental chemistry. The risks related to MPs include their capability to adsorb toxic and harmful molecular species, and to release additives and degradation products into ecosystems. Their role as a primary source of a broad range of harmful volatile organic compounds (VOCs) has also been recently reported.In this work, we applied a non-destructive approach based on selected-ion flow tube mass spectrometry (SIFT-MS) for the characterization of VOCs released from a set of plastic debris collected from a sandy beach in northern Tuscany.The interpretation of the individual SIFT-MS spectra, aided by principal component data analysis, allowed us to relate the aged polymeric materials that make up the plastic debris (polyethylene, polypropylene, and polyethylene terephthalate) to their VOC emission profile, degradation level, and sampling site. The study proves the potential of SIFT-MS application in the field, as a major advance to obtain fast and reliable information on the VOCs emitted from microplastics. The possibility to obtain qualitative and quantitative data on plastic debris in less than 2 min also makes SIFT-MS a useful and innovative tool for future monitoring campaigns involving statistically significant sets of environmental samples

Novel application of liquid chromatography/mass spectrometry for the characterization of drying oils in art: Elucidation on the composition of original paint materials used by Edvard Munch (1863-1944)

Modern oil paints, introduced at the beginning of the 20th century, differ from those classically used in antiquity in their chemical and compositional features. The main ingredients were still traditional drying oils, often used in mixtures with less expensive oils and added with several classes of additives. Consequently, detailed lipid profiling, together with the study of lipid degradation processes, is essential for the knowledge and the conservation of paint materials used in modern and contemporary art.A multi-analytical approach based on mass spectrometry was used for the study of original paint materials from Munch's atelier, owned by the Munch Museum in Oslo. The results obtained in the analysis of paint tubes were compared with those obtained by characterizing a paint sample collected from one of the artist's sketches for the decoration of the Festival Hall of the University of Oslo (1909-1916).Py-GC/MS was used as screening method to evaluate the presence of lipid, proteic or polysaccaridic materials. GC/MS after hydrolysis and derivatization allowed us to determine the fatty acid profile of the paint tubes, and to evaluate the molecular changes associated to curing and ageing. The determination of the fatty acid profile is not conclusive for the characterization of complex mixtures of lipid materials, thus the characterization of the triglyceride profiles was performed using an analytical procedure based on HPLC-ESI-Q-ToF.This paper describes the first application of HPLC-ESI-Q-ToF for the acquisition of the triglyceride profile in a modern paint sample, showing the potentialities of liquid chromatography in the field of lipid characterization in modern paint materials. Moreover, our results highlighted that the application of this approach can contribute to address dating, authenticity and conservation issues relative to modern and contemporary artworks

New methodologies for the detection, identification, and quantification of microplastics and their environmental degradation by-products

Sampling, separation, detection, and characterization of microplastics (MPs) dispersed in natural water bodies and ecosystems is a challenging and critical issue for a better understanding of the hazards for the environment posed by such nearly ubiquitous and still largely unknown form of pollution. There is still the need for exhaustive, reliable, accurate, reasonably fast and cost efficient analytical protocols allowing the quantification not only of MPs, but also of nanoplastics (NPs) and of the harmful molecular pollutants that may result from degrading plastics. Here a set of newly developed analytical protocols, integrated with specialized techniques such as pyrolysis-gaschromatography-mass spectrometry (Py-GC/MS), for the accurate and selective determination of the polymers most commonly found as MPs polluting marine and freshwater sediments are presented. In addition, the results of an investigation on the low molecular weight volatile organic compounds (VOCs) released upon photo-oxidative degradation of microplastics highlight the important role of photoinduced fragmentation at a molecular level both as a potential source of hazardous chemicals and as accelerators of the overall degradation of floating or stranded plastic debris

Textiles and environment in the showcase containing Saint Canute the Holy († AD 1086):Radiocarbon dating and chemical interactions

The cathedral in Odense, Denmark, has for nine centuries held the relics of the Danish King St Canute the Holy and his brother Benedikt. They were both murdered in the predecessor church at the site in AD 1086, and Canute was sanctified in already in AD 1100. The history of the relics has been that of turmoil at times, varying from initial worship of the Catholic believers, to being walled up and hidden away after the protestant reformation in AD 1536, and since the 19th Century on display as important heritage objects of national importance. In the present work we have characterised some of the textiles and analysed the air inside the glass showcases exhibiting the 11th Century wooden coffins holding the remains of St King Canute the Holy and his brother together with some precious textiles. Contrary to previous belief, we now prove that all the textiles analysed have the same age, which is consistent with the time of the enshrinement of the King and his brother in AD 1100. It is also shown that some of the textiles were treated with paraffin wax, most likely during attempts at conservation at the National Museum in the nineteenth century. The results of the air chemistry analyses show the problematic side of simultaneously storing of slowly decaying wood, fine textiles, and human bones in rather airtight environments. The wood continuously releases organic acids, the soaring concentrations of which are potentially harmful to the 11th Century textiles and probably also to the bones