Colored inks analysis and differentiation: a first step in artistic contemporary prints discrimination

Prints are the most popular artistic technique. Due to their manufacturing procedure, they are also one of the most frequently falsified types of artwork. In terms of their economic and historic value, the chemical analysis and characterisation of coloured inks and their principal constituent materials (pigments), together with the historical and aesthetic information available in the Catalogues Raisonées, are important tools in distinguishing originals from non-original prints.The chemical characterisation and discrimination of coloured inks has test in this study. Analysis using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and X-ray diffraction (XRD) has been done on blue pigments and inks, due to this colour is one of the most representative for the presence of organic and inorganic materials in their composition. Conclusion obtained for this colour would demonstrate the capability of the approach when it is applied to any other coloured set of inks.     

ATR and transmission analysis of pigments by means of far infrared spectroscopy

In the field of FTIR spectroscopy, the far infrared (FIR) spectral region has been so far less investigated than the mid-infrared (MIR), even though it presents great advantages in the characterization of those inorganic compounds, which are inactive in the MIR, such as some art pigments, corrosion products, etc. Furthermore, FIR spectroscopy is complementary to Raman spectroscopy if the fluorescence effects caused by the latter analytical technique are considered. In this paper, ATR in the FIR region is proposed as an alternative method to transmission for the analyses of pigments. This methodology was selected in order to reduce the sample amount needed for analysis, which is a must when examining cultural heritage materials. A selection of pigments have been analyzed in both ATR and transmission mode, and the resulting spectra were compared with each other. To better perform this comparison, an evaluation of the possible effect induced by the thermal treatment needed for the preparation of the polyethylene pellets on the transmission spectra of the samples has been carried out. Therefore, pigments have been analyzed in ATR mode before and after heating them at the same temperature employed for the polyethylene pellet preparation. The results showed that while the heating treatment causes only small changes in the intensity of some bands, the ATR spectra were characterized by differences in both intensity and band shifts towards lower frequencies if compared with those recorded in transmission mode. All pigments' transmission and ATR spectra are presented and discussed, and the ATR method was validated on a real case study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Spectroscopic investigation of a ‘Virgin of Sorrows’ canvas painting: A multi-method approach

The investigation of unmatched ancient objects is an attentive and arduous activity to conservation scientists. An important aspect of art analysis is the question on sampling and avoiding damage on the artefact during the study. A possible way to maximize the information that is extracted from the historical object is using several sensitive micro-analytical techniques on the same micro samples. As an illustration of this multi-method approach, in this work, a canvas painting ‘Virgin of Sorrows’ was studied and its materials were analysed in order to roughly date and to authenticate this object of art. Proton induced X-ray emission (PIXE), neutron activation analysis (NAA), optical microscopy, scanning electron microscopy (SEM), micro-Raman spectroscopy (MRS) and Fourier transform infrared spectroscopy (FT-IR) were used, obtaining successful results. These methods allowed identifying the different inorganic pigments (iron oxide, carbon black, white lead, Prussian blue) as well as indigo. Optical microscopy and SEM revealed the layered structure of the samples, while FT-IR enabled to determine the nature of the varnish used (shellac). By using these complementary techniques, it was possible to identify the materials in the painting, which are indicative for the period of manufacturing the artwork.     

Joseph Beuys und die Braunkreuzfarbe

X‐Ray fluorescence analysis is a non‐destructive key‐technique in the study of pigments in art objects. The technique also qualifies as a tool for the classification of a unique group of artwork created by the artist Joseph Beuys. The Origin of his Braunkreuz‐Colour has been vividly discussed. Physical and chemical methods can discriminate between at least two categories of Braunkreuz‐objects in the Oeuvre of the artist.     

On-line FT-Raman and dispersive Raman spectra database of artists’ materials (e-VISART database)

Raman spectroscopy has been widely applied in the analysis of different types of artwork. This technique is sensitive, reliable, non-destructive and can be used in situ. However, there are few references in the literature regarding specific Raman spectra libraries for the field of artwork analysis. In this paper, the development of two on-line databases with Fourier transform Raman (FT-Raman; 1064 nm) and dispersive Raman (785 nm) spectra of materials used in fine art is presented; both are implemented in the e-vibrational spectroscopic databases of artists materials database (e-VISART). The database provides not only spectra, but also information about each pigment. It must be highlighted that for each pigment or material several spectra are available from different dealers. Some of the FT-Raman spectra available in the e-VISART database have not been published until now. Some examples in which the e-VISART database has been successfully used are presented.     

Chemical composition of contemporary black printing inks based on infrared spectroscopy: basic information for the characterization and discrimination of artistic prints

This article aims to provide the basic information necessary to afford the discrimination of artistic prints based on chemical information. The presence of original and non-original prints in the art market is a real problem, especially for contemporary artists. Most of the non-original elements can be distinguished on the basis of their stylistics and printing characteristics, but sometimes this information is not enough. To facilitate discrimination in these cases, we propose to add, to the previously indicated aspects, the chemical information of the materials involved in the production of the original series (inks, paper and pencil). Comparison of the composition of any element with that established for the original series will permit the attribution of any doubtful element. This article is focused on the evaluation of this approach by determining the chemical composition of contemporary black printing inks by infrared spectroscopy and by searching, on the basis of the information obtained, for criteria capable to discriminate between prints made of different inks. The success of the approach with this set of inks could easily be extended to the study of colour inks. The study also includes the characterization and discrimination of black pigments because they are the most characteristic component of these inks and because this information can also be useful for other artistic studies. The procedure proposed permits the analysis of inks with minimum deterioration of the artwork. Results indicate the capability of the approach because, following the procedure, it is possible to distinguish between black pigments attending to the presence of hydroxyapatite, silicate and some other specific bands, whereas black inks can be discriminated by paying attention to the inclusion in their composition of such pigments as bone black, Prussian blue, mars brown or other specific bands. Scanning electron microscopy analyses have corroborated the results obtained.     

苯丙胺类毒品及其衍生物的气相色谱-红外光谱分析

采用气相色谱一傅立叶变换红外光谱联用技术,建立了9种苯丙胺类毒品及其衍生物的分析鉴别方法.采用HP-1(30 m×0.32 mm,0.25 μm)毛细管柱,MCT红外检测器与氢火焰检测器同时检测,在程序升温条件下,以十七烷为内标物,研究已知对照品的色谱保留行为及其气态红外光谱图特征,建立相应的特征吸收峰数据库,作为鉴别分析的依据.色谱保留时间与红外特征吸收峰联合鉴别法极大地提高了鉴别的准确性.将发展的方法应用于可疑毒品物证中苯丙胺类及其衍生物毒品样品的鉴别,获得了理想的结果.本方法可用于涉毒案件毒品物证的检验,特别适用于混合毒品成分的检验.     

Studies of wall painting fragments from Kaiping Diaolou by SEM/EDX, micro Raman and FT-IR spectroscopy

The multi-technique analytical approach has proved to be a very effective tool for the analysis of artwork, as demonstrated by various studies. In this work, four micro-analysis methods were used to analyze the wall painting fragments in Kaiping Diaolou, a world cultural heritage enlisted in 2007. Field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray micro-analysis (EDX), combined with micro Raman and Fourier transform infrared (FT-IR) spectroscopy, provided a vast amount of information concerning the raw materials present in the pigments, organic binder, plasters and mortars of the wall painting. Four types of pigments (goethite, lazurite, chromium green and calcite) were identified on the surface layer of the wall paintings. The substrate under the pigment layer was found to be composed of cubic-like calcite (CaCO₃), micro-rod bundle-shaped syngenite (K₂Ca(SO₄)₂·H₂O), gypsum (CaSO₄·2H₂O) and silica (SiO₂). The organic binder can be attributed to animal glue (such as egg) and drying oil by micro FT-IR spectroscopy. These analysis results can provide important information for the conservation and restoration of the Kaiping Diaolou.     

Detection of Casting Material on Historical Violins by Infrared Spectroscopy and Total Reflection X-Ray Fluorescence Spectrometry

Abstract

Infrared spectroscopy and total reflection X-ray fluorescence spectrometry are used for the analysis of historical varnishes. Total reflection X-ray fluorescence spectrometry is used in the analysis of the elemental composition; infrared spectroscopy is used to determine the inorganic and organic molecules of the binding media, pigments and additives. On historical violins made by A. Guarneri and L. Widhalm silicon and tin were found by total reflection X-ray fluorescence spectrometry. Silicon was proved to be present in the form of silicon rubber by infrared spectroscopy. A further experiment confirmed that the treatment of a violin with silicon rubber casting material is detectable.     

Benefits of applying combined diffuse reflectance FTIR spectroscopy and principal component analysis for the study of blue tempera historical painting

This paper explores the application of diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to the examination of historic blue pigments and blue tempera paintings commonly found on works of art. The discussion is mainly focused on the practical benefits of using this technique joined to principal component analysis (PCA), a powerful multivariate analysis tool. Thanks to the study of several replica samples that contain either pure blue pigments (azurite, lapis lazuli and smalt), or pure binder (rabbit glue) and mixtures of each of the pigments with the binder (tempera samples), different aspects of these benefits are highlighted. Comparative results of direct spectra and multivariate analysis using transmittance-Fourier transform infrared spectroscopy (T-FTIR) are discussed throughout this study. Results showed an excellent ability of PCA on DRIFT spectra for discriminating replica samples according to differing composition. Several IR regions were tested with this aim; the fingerprint IR region exhibited the best ability for successfully clustering the samples. The presence of the binder was also discriminated. Only using this approach it was possible to completely separate all the studied replica samples. This demonstrates the potential benefits of this approach in identifying historical pigments and binders for conservation and restoration purposes in the field of Cultural Heritage.     

Earth pigments in painting: characterisation and differentiation by means of FTIR spectroscopy and SEM-EDS microanalysis

Analytical characterisation of natural earths (ochres, siennas, umbers and green earths) has been carried out using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) coupled to an energy dispersive X-Ray spectrometer (EDS). The study of these pigments, which are found in works of art, is very important since it can shed light on their source or the pictorial technique used. FTIR spectroscopy is suitable for the identification and differentiation of ochres and siennas. According to the matrix of the sample, FTIR allows the classification of ochres into ochres containing kaolinite and ochres containing sulphate. One of the goals of this research has been to establish a relationship between the matrix and the source of the samples tested. SEM-EDS is probably a better technique than FTIR for characterising umbers and green earths since they do not exhibit significant differences when FTIR studies are performed.     

Use of near infrared spectroscopy in a study of binding media used in paintings

The present study illustrates the use of near infrared spectroscopy in the conservation and restoration field. This application of the technique, widely used in other fields such as the agricultural and food industries, is very interesting due to two of its features: rapidity and non-destructiveness. In this study, three classification algorithms have been used to attempt to correlate the spectra of the samples under study—mixtures of two pigments (one organic and the other inorganic)—with binder recipes found in literature. Some of these recipes have very similar compositions, but they were distinguished into groups, depending on the painting technique associated with them.     

ATR-FT-IR spectroscopy in the region of 550–230 cm−1 for identification of inorganic pigments

A comprehensive study of ATR-FT-IR spectra of 40 inorganic pigments of different colours widely used in historical paintings has been carried out in the low wave number spectral range (550–230 cm^?1). The infrared spectra were recorded from mixtures of pigment and linseed oil. It is demonstrated that this spectral range – essentially devoid of absorption peaks of the common binder materials – can be well used for identification of inorganic pigments in paint samples thereby markedly extending the possibilities of pigment identification/confirmation by ATR-IR spectroscopy into the realm of pigments having no absorptions in the mid-IR region. In some cases the method can be used alone for pigment identification and in many cases it provides useful additional evidence for pigment identification using other instrumental techniques (electron microprobe analysis, XRF, optical microscopy). Together with earlier work this study provides a comprehensive overview of the pigment identification possibilities using ATR-FT-IR as well as a collection of reference spectra and is expected to be a useful reference for conservation practitioners.     

Simultaneous Raman and infrared spectroscopy: a novel combination for studying bacterial infections at the single cell level

Sepsis is a life-threatening clinical condition responsible for approximately 11 million deaths worldwide. Rapid and accurate identification of pathogenic bacteria and its antimicrobial susceptibility play a critical role in reducing the morbidity and mortality rates related to sepsis. Raman and infrared spectroscopies have great potential to be used as diagnostic tools for rapid and culture-free detection of bacterial infections. Despite numerous reports using both methods to analyse bacterial samples, there is to date no study collecting both Raman and infrared signatures from clinical samples simultaneously due to instrument incompatibilities. Here, we report for the first time the use of an emerging technology that provides infrared signatures via optical photothermal infrared (O-PTIR) spectroscopy and Raman spectra simultaneously. We use this approach to analyse 12 bacterial clinical isolates including six isolates of Gram-negative and six Gram-positive bacteria commonly associated with bloodstream infection in humans. To benchmark the single cell spectra obtained by O-PTIR spectroscopy, infrared signatures were also collected from bulk samples via both FTIR and O-PTIR spectroscopies. Our findings showed significant similarity and high reproducibility in the infrared signatures obtained by all three approaches, including similar discrimination patterns when subjected to clustering algorithms. Principal component analysis (PCA) showed that O-PTIR and Raman data acquired simultaneously from bulk bacterial isolates displayed different clustering patterns due to the ability of both methods to probe metabolites produced by bacteria. By contrast, signatures of microbial pigments were identified in Raman spectra, providing complementary and orthogonal information compared to infrared, which may be advantageous as it has been demonstrated that certain pigments play an important role in bacterial virulence. We found that infrared spectroscopy showed higher sensitivity than Raman for the analysis of individual cells. Despite the different patterns obtained by using Raman and infrared spectral data as input for clustering algorithms, our findings showed high data reproducibility in both approaches as the biological replicates from each bacterial strain clustered together. Overall, we show that Raman and infrared spectroscopy offer both advantages and disadvantages and, therefore, having both techniques combined in one single technology is a powerful tool with promising applications in clinical microbiology.

O-PTIR was used for simultaneous collection of infrared and Raman spectra from clinical pathogens associated with bloodstream infections.     

Composition of prehistoric rock-painting pigments from Egypt (Gilf Kébir area)

The composition of rock-painting pigments from Egypt (Gilf Kebia area) has been analyzed by means of molecular spectroscopy such as Fourier transform infrared and micro-Raman spectroscopy and scanning electron microscopy coupled to an energy dispersive X-ray spectrometer and X-ray fluorescence analysis. Red and yellow pigments were recognized as red and yellow ochre with additional rutile.     

Influence of composition and roughness on the pigment mapping of paintings using mid-infrared fiberoptics reflectance spectroscopy (mid-IR FORS) and multivariate calibration

Mid-infrared fiberoptics reflectance spectroscopy (mid-IR FORS) is a very interesting technique for artwork characterization purposes. However, the fact that the spectra obtained are a mixture of surface (specular) and volume (diffuse) reflection is a significant drawback. The physical and chemical features of the artwork surface may produce distortions in the spectra that hinder comparison with reference databases acquired in transmission mode. Several studies attempted to understand the influence of the different variables and propose procedures to improve the interpretation of the spectra. This article is focused on the application of mid-IR FORS and multivariate calibration to the analysis of easel paintings. The objectives are the evaluation of the influence of the surface roughness on the spectra, the influence of the matrix composition for the classification of unknown spectra, and the capability of obtaining pigment composition mappings. A first evaluation of a fast procedure for spectra management and pigment discrimination is discussed. The results demonstrate the capability of multivariate methods, principal component analysis (PCA), and partial least squares discrimination analysis (PLS-DA), to model the distortions of the reflectance spectra and to delimitate and discriminate areas of uniform composition. The roughness of the painting surface is found to be an important factor affecting the shape and relative intensity of the spectra. A mapping of the major pigments of a painting is possible using mid-IR FORS and PLS-DA when the calibration set is a palette that includes the potential pigments present in the artwork mixed with the appropriate binder and that shows the different paint textures. Graphical Abstract

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Separation and tentative identification of the main pigment fraction of raisins by thin-layer chromatography-Fourier transform infrared and high-performance liquid chromatography-ultraviolet detection

The soluble color pigments of raisin are separated by reversed-phase thin-layer chromatography (TLC), and the capacity of TLC-Fourier transform infrared (FTIR) with both on-line and off-line coupling is assessed for the identification of the main fraction. TLC has also been used as a pilot technique for the development of a gradient elution method for the separation of pigments by high-performance liquid chromatography (HPLC). On-line TLC-FTIR cannot be used for identification because of the strong adsorbance of the stationary phase. Off-line TLC-FTIR combined with the retention behavior of the main pigment fraction indicates that it is a polymer, caramel-like compound composed of erythrose and fructose monomers. Baseline separation of pigments is achieved by HPLC using TLC as a pilot method.     

Synthesis of IONP's decorated graft copolymers and study of their magnetic force–induced wastewater treatment

Our work is focused on facile synthesis and modification of amylopectin‐grafted block copolymers by using reversible addition?fragmentation chain transfer (RAFT) polymerization technique. This technique yields polymers with controlled molecular weight and low polydispersity indexes and is feasible with a wide range of monomers. Five different grades of amylopectin‐grafted polymethacrylic acid and polyacrylamide block copolymers have been synthesized via RAFT, by varying the amount of acrylamide employing amylopectin‐based macro chain transfer agent. Graft copolymers have been upgraded as smart responsive graft copolymers, through the incorporation of iron oxide nanoparticles (IONPs) via condensation reaction. The polymeric materials have been extensively characterized by energy‐dispersive X‐ray analysis, Fourier transform infrared spectroscopy, proton magnetic resonance spectroscopy, scanning electron microscopy, ultraviolet‐visible spectroscopy, gel permeation chromatography, transmission electron microscopy, thermogravimetric analysis, and X‐ray diffraction analysis. Normal and responsive graft copolymers have been studied for removal of model contaminant (kaolin), and responsive graft copolymers have been used to remove methylene blue dye (without using any adsorbent) from water by applying external magnetic field. The upgraded block copolymers have shown best performance in wastewater treatment.     

Noninvasive and nondestructive NMR, Raman and XRF analysis of a Blaeu coloured map from the seventeenth century

A complete multianalytical study of a hand-coloured map from the seventeenth century is presented. The pigments atacamite, massicot, minium, gypsum, carbon black and vermilion were determined by means of XRF and Raman spectroscopy. The state of conservation of the cellulosic support was monitored by means of unilateral NMR. The analysis was nondestructive and noninvasive, and thus several spectra were collected from the same areas, yielding more reliable results without damaging the artwork. The role of copper pigments in the oxidation processes observed in the cellulosic support is discussed, as well as the possible provenance of atacamite as a raw material instead of as a degradation product of malachite.     

Structures and colour properties of new red wine pigments

Two new red pigments were synthesized by nucleophilic addition of vinylphenols to malvidin 3-glucoside. The structures of the resulting pyranoanthocyanins were confirmed by electrospray-mass spectrometry and NMR spectroscopy (gHMQC, gHMBC and CIGAR experiments). By means of UV-vis spectroscopy the colour properties of the pigments were characterized; it could be demonstrated that the pyranoanthocyanins retained their red colour at pH 3.6 in model wine and were resistant to bisulfite-mediated bleaching. Finally, HPLC-MS analysis confirmed the presence of both anthocyanin-derived pigments in red wine.