Studies on paint cross sections of a glass painting by using FT‐IR and Raman microspectroscopy supported by univariate and hierarchical cluster analyses

Fourier transform infrared (FT‐IR) and Raman spectroscopy is used for the non‐destructive analysis of painting materials and ageing compounds in micrometric cross sections of a glass painting. The combination of both techniques in conjunction with imaging/mapping function provides the spatial distribution of chemical components identified in vibrational spectra. The aim of our work is to show the applicability of the FT‐Raman mapping technique in the detection of painting materials. We also compare Raman information gained by using two laser excitations at 532 and 1064 nm implemented in microspectrometers with different confocality and spatial resolution. In turn among FT‐IR imaging techniques, we compare chemical images recorded in external reflection and attenuated total reflection modes that give chemical images of different size and spatial resolution. Our FT‐IR and Raman imaging characterize a number of painting materials such as pigments, binders, fillers as well as degradation products. Raman maps are constructed by using the univariate analysis. In turn, a profile of IR images requires the use of a more complex methodology. Here, we compare FT‐IR images of the painting cross sections obtained by using the univariate and hierarchical cluster analysis. We clearly show that the multivariate approach is a powerful tool for the credible construction of IR images, providing the relevant chemical information on the multicomponent stratigraphy of the samples. Moreover, the combination of all the methods allows us to demonstrate their degree of utility for the study on the paint cross sections of the works of art. Copyright © 2013 John Wiley & Sons, Ltd.     

Microanalysis of clay‐based pigments in painted artworks by the means of Raman spectroscopy

FT Raman spectroscopy and micro‐Raman spectroscopy with lasers of three different wavelengths (1064 nm, 785 nm and 532 nm) were used for analysis of reference samples of natural clay pigments including white clay minerals (kaolinite, illite, montmorillonite), green earths (glauconite and celadonite) and red earths (natural mixtures of white clay minerals with hematite). In addition, eight micro‐samples obtained from historical paintings containing clay pigments in ground and colour layers have been examined. Powder X‐ray diffraction and micro‐diffraction were used as supplementary methods. It was found that laser operating at 1064 nm provided the best quality Raman spectra for distinguishing different white clay minerals, but the spectra of green and red earths were affected by strong fluorescence caused by the presence of iron. Green earth minerals could be easily distinguished by 532 or 785 nm excitation lasers, even in small concentrations in the paint layers. On the other hand, when anatase (TiO₂) or iron oxides (such as hematite) were present as admixtures (both are quite common, particularly in red earths), the collection of characteristic spectra of clay minerals which form the main component of the layer was hindered or even prevented. Another complicating factor was the fluorescence produced by organic binders when analysing the micro‐samples of artworks. In those cases, it is always necessary to use powder X‐ray micro‐diffraction to avoid misleading interpretations of the pigment's composition. Copyright © 2013 John Wiley & Sons, Ltd.     

Forensic analysis of automotive paints by Raman spectroscopy

In this work, the possible contribution of Raman spectroscopy in forensic science is evaluated, more specifically for the analysis of automotive paint samples. Spectra from paint flakes as well as from cross sections were examined, in order to identify not only the pigments but also binders and extenders in all paint layers. Moreover, the possibility of distinguishing paint samples from different cars was evaluated to assess the use of vibrational spectroscopic techniques in the investigation of a hit-and-run accident. The presence of rutile and extenders, such as calcite and barium sulphate, could be demonstrated by their characteristic Raman bands. However, the identification of the binder by Raman spectroscopy was hampered: only with additional information from IR analysis could most of the bands in the spectrum be assigned to molecular vibrations of the binders. In contrast, organic pigments, having very distinctive and well-resolved characteristic bands, could easily be identified by comparing the spectra from the basecoat of the sample with spectra from a reference database. Because of these characteristic bands, the basecoat seems to provide the best spectra to distinguish paint samples. Moreover, some paints can also be distinguished by the absence or presence of the bands from calcium carbonate and barium sulphate in the primer surfacer. When recording spectra from paint flakes, Raman bands from the spectra of the clearcoat as well as from the basecoat are obtained. Copyright © 2005 John Wiley & Sons, Ltd.     

Surface‐enhanced Raman scattering (SERS) and complementary techniques applied for the investigation of an Italian cultural heritage canvas

A cultural heritage canvas from the early 19^th century, painted by the Vaccaro brothers for the church of Niscemi, province of Caltanissetta, Sicily, was analyzed using Fourier transform (FT)‐Raman, attenuated total reflectance‐FT‐infrared and surface enhanced Raman scattering (SERS) spectroscopy. The painting, still used in religious rites related to the Easter mass (‘la calata da tila’), depicts the scene of the Crucifixion and is executed in a scarce palette, with white, green and blue colors. Analysing vibrational data in conjunction with scanning electron microscopy and solid ‐state ¹³C‐NMR signals of the linen threads, we were able to offer valuable insight into the painting technique, unknown prior to this study. SERS is usually employed in artwork diagnosis for the identification of organic lakes and dyes. Due to its sensitivity, SERS has been successfully applied for the detection of either organic painting materials (indigo) that are usually not resolved by conventional Raman spectroscopy or of inorganic pigments difficult to observe in the presence of highly fluorescent aged organic supports or binders. To the best of our knowledge, this is also the first report on the SERS investigation of flax used in linen from cultural heritage objects using Ag colloidal nanoparticles. Copyright © 2012 John Wiley & Sons, Ltd.     

Assessment of Raman microscopy coupled with principal component analysis to examine egg yolk–pigment interaction based on the protein C?H stretching region (3100–2800 cm−1)

This work seeks to identify the slight changes in the characteristic C H stretching region (3100–2800 cm⁻¹) of a protein‐based binder and fatty acid esters from egg yolk, which may occur in complex paint samples due to the presence of particular pigments. To date, this protein region—where historic pigments do not show characteristic Raman bands—has not been used to identify possible interactions between painting materials, in spite of its potential due to the mentioned feature. This study is based on the investigation of pure egg yolk model samples and tempera model samples prepared by mixing this binder with some historic pigments (cinnabar, raw Sienna, lead white, gypsum, calcite, azurite, lapis lazuli and smalt) as binary samples. All samples were analyzed in this region by Raman microscopy (RM) coupled with principal component analysis (PCA) for three color groups (red, white and blue) separately. The results show relevant spectral changes in the C H stretching region of amino acids and polyunsaturated fatty acids esters of the egg yolk binder, particularly in the azurite, lead white and gypsum‐based tempera samples. Lesser interactions were discerned in the tempera samples made with smalt, as well as shift in the region of polyunsaturated fatty acid esters of the egg yolk binder in the cinnabar and raw Sienna‐based tempera paintings. No interactions were recognized between the egg yolk and the pigments calcite and lapis lazuli. The effectiveness of applying RM combined with PCA for identifying interaction processes between binders and pigments is demonstrated. Copyright © 2011 John Wiley & Sons, Ltd.     

Characterisation and classification of automotive clear coats with Raman spectroscopy and chemometrics for forensic purposes

The clear coats from a collection of automotive paint samples of 139 vehicles, covering a range of Australian and international vehicle manufacturers and sold in Western Australia, were characterised using FT‐Raman spectroscopy. Principal component analysis (PCA) revealed 19 distinct classes that were associated with the vehicles' manufacturer and model, and in the case of Australian manufacturers, the years of manufacture. Linear discriminant analysis based on the PCA groupings gave excellent discrimination between the groups with 96.9% of the calibration set and 97.6% of the validation set being correctly classified. Although the sample set comprised only vehicles available in Australia, the methodology used is universal and hence applicable in any jurisdiction that is willing and able to generate a statistically significant data set and maintain and update it as new vehicles appear on the market. A FT‐Raman spectroscopy‐based database would rapidly provide information regarding vehicle origin and manufacture and hence generate investigative leads for questioned paint samples found at incident sites. Copyright © 2016 John Wiley & Sons, Ltd.     

Discrimination of carotenoid and flavonoid content in petals of pansy cultivars (Viola x wittrockiana) by FT‐Raman spectroscopy

Fourier Transform Raman spectroscopy (FT‐Raman) has been applied for the non‐destructive in‐situ analysis of pigments on differently colored flower petals of pansy cultivars (Viola x wittrockiana). The main target of the present study was to investigate how far the Raman mapping technique through FT‐Raman spectroscopy and cluster analysis of the Raman spectra is a potential method for the direct, in‐situ discrimination of flavonoids (flavonols against anthocyanins) and of carotenoids occurring in flowers, using intact and differently colored flower petal of Viola x wittrockiana for this case study. In order to get more information about the reliability of the direct in‐situ flavonoid detection by the Raman method, pigments extracts of the petals were separated by thin‐layer chromatography (TLC) and investigated by Raman spectroscopy. Hierarchical cluster analysis (HCA) of the Raman spectra from reference pigments (carotenoids, anthocyanins and flavonols), from areas of the flower petals, and from the TLC extracts allowed discriminating the various pigments, in particular flavonoids (flavonols against anthocyanins) and carotenoids. With a two‐dimensional Raman mapping technique, which provides a chemical image of the sample under investigation, we determined by cluster analysis the distribution of carotenoids, anthocyanins and flavonols from the outer layer of the petals, and by integrating through suitable spectral regions selected as characteristic markers for particular pigments their relative concentration could approximately be determined. We found a satisfactory correlation between the patterns seen on the visible images and the patterns on the chemical images obtained by Raman mapping. Copyright © 2011 John Wiley & Sons, Ltd.     

Fourier‐transform Raman analysis of milk powder: a potential method for rapid quality screening

In this work, FT‐Raman spectroscopy was explored as a fast and reliable screening method for the assessment of milk powder quality and the identification of samples adulterated with whey (1–40% w/w). Raman measurements can easily differentiate milk powders without the need of sample preparation, whereas the traditional methods of quality control, including high‐performance liquid chromatography, are laborious and slow. The FT‐Raman spectra of whole, low‐fat, and skimmed milk powder samples were obtained and distinguished from commercial milk powder samples. In addition, the exploratory analysis employing data from Raman spectroscopy and principal component analysis (PCA)allowed the separation of milk powder samples according to type,identifying differences between samples in the same group. Multivariate analysis was also developed to classify the adulterated milk powder samples using PCA and partial least squares discriminate analysis (PLS‐DA). The resulting PLS‐DA model correctly classified 100% of the adulterated samples. These results clearly demonstrate the utility of FT‐Raman spectroscopy combined with chemometrics as a rapid method for screening milk powder. Copyright © 2011 John Wiley & Sons, Ltd.     

Raman spectroscopy at different excitation wavelengths (1064, 785 and 532 nm) as a tool for diagnosis of colon cancer

Raman spectroscopy is structure sensitive non‐destructive method that allows observing the status of biological tissues with minimal impact. This method has a great potential in the diagnosis of various types of degenerative diseases including cancer damages. Near‐infrared Fourier transform (NIR‐FT)‐Raman (λ_ex ~1064 nm), NIR‐visible (Vis)‐Raman (λ_ex ~785 nm) and Vis‐Raman (λ_ex ~532 nm) spectra of normal and colorectal carcinoma colon tissue samples were recorded in macroscopic mode at 10–20 randomly chosen independent sites. In the cases of NIR‐Vis‐ and Vis‐Raman spectra, enhanced resonance effects were observed for tissue chromophores absorbing in the visible area. Evident spectral differences were noticed for Raman spectra of normal colon tissue samples in comparison with abnormal samples. The average Raman spectra of colon tissue samples were analysed by principal component analysis (PCA) to discriminate normal and abnormal tissues. PCA of combined dataset containing Raman intensities of chosen NIR‐FT, NIR‐Vis or Vis‐Raman bands led to discrimination of normal and abnormal colon tissue samples. Therefore, combination of these three Raman methods can be helpful for recognizing cancer lesions in colon for diagnostic purposes. Copyright © 2014 John Wiley & Sons, Ltd.     

Identification of Raman spectra through a case‐based reasoning system: application to artistic pigments

This paper presents a methodology conceived as a support system to identify unknown materials by means of the automatic recognition of their Raman spectra. Initially, the design and implementation of the system were framed in an artistic context where the Raman spectra analyzed belong to artistic pigments. The analysis of the pigmentation used in an artwork constitutes one of the most important contributions in its global study. This paper proposes a methodology to systematically identify Raman spectra, following the way analysts usually work in their laboratory but avoiding their assessment and subjectivity. It is a three‐phase methodology that automates the spectral comparison, which is based on one of the most powerful paradigms inmachine learning: the case‐based reasoning (CBR) systems. A CBR system is able to solve a problem by using specific knowledge of previous experiences (well‐known spectral library of patterns) and finding the most similar past cases (patterns), reusing and adapting them to the new problem situation (unknown spectrum). The system results in a global signal processing methodology that includes different phases such as reducing the Raman spectral expression by means of the principal component analysis, the definition of similarity measures to objectively quantify the spectral similarity and providing a final value obtained by a fuzzy logic system that will help the analyst to take a decision. The major benefit of a Raman spectral identification system lies in offering a decision‐support tool to those who are not experts or under difficult situations with respect to Raman spectroscopy. Copyright © 2011 John Wiley & Sons, Ltd.     

Discrimination of aged mixtures of lipidic paint binders by Raman spectroscopy and chemometrics

This work explores the application of chemometric techniques to Raman spectra to study aged lipidic paint binders. These binders, commonly known as drying oils, were widely used by artists throughout history both individually and in mixtures. We prepared various model samples of the pure binders (linseed, poppy‐seed and walnut oils and egg yolk) and of binary mixtures thereof. These model samples were left to age naturally for six years and further characterized by Raman spectroscopy. A comparative study of the Raman spectral features before and after ageing process was carried out. This showed changes mainly in the bands located at 1267, 1655 and 3011 cm^–1, which correspond to vibrations in cis double bonds. Multivariate analysis was performed by applying principal component analysis and partial least‐squares discriminant analysis on the corresponding Raman spectra to test whether spectral differences allowed samples to be distinguished on the basis of their composition. The CH stretching region was found to be especially useful for discrimination between the different binders. Furthermore, good sensitivity and specificity were found in the discriminant analysis particularly for the identification of binders containing egg yolk. The results of these multivariate analyses demonstrated the potential use of both chemometric approaches in the field of Cultural Heritage for drying oil characterization and identification, and also for gaining a deeper insight into the ageing process. Copyright © 2011 John Wiley & Sons, Ltd.     

Raman spectroscopy of synthetic organic pigments used in 20th century works of art

Raman microscopy allows a non‐destructive characterisation of inorganic and organic painting materials such as pigments and organic dyestuffs. The objectives of this study are the more recent organic pigments typically present in paintings and other art works from the 20th century. More than 20 organic synthetic pigments from different chemical classes could be identified by Raman spectroscopy using different excitation wavelengths (457.9, 476.5, 487.9, 514.5, 632.8, and 1064 nm). To evaluate the performance for real paint samples, varying paint mixtures of the Hansa Yellow pigment PY 3 and the binding medium Mowilith, a polyvinyl acetate (PVAC) compound, were characterised; PY 3 was determined at a 1 wt% level in the binder. In addition, commercial tube paints containing the quinacridone violet PV 19 were studied. The pigment was clearly identified in all of these more complex oil and acrylic paints. Finally, alizarin (PR 83) and a green copper phthalocyanine pigment (PG 7) could unambiguously be identified by Raman microscopy in the painting ‘Woman with mandolin in yellow and red’ of Max Beckmann dating 1950. The discovery of a red naphthol AS pigment by Raman spectroscopy in a sample from the ‘Three field workers’ by Georg Baselitz (1964/1965) demonstrated that in some cases complementary chromatographic methods are needed for a comprehensive identification of the organic pigments. Copyright © 2008 John Wiley & Sons, Ltd.     

Collagen-based proteinaceous binder-pigment interaction study under UV ageing conditions by MALDI-TOF-MS and principal component analysis

This study focuses on acquiring information on the degradation process of proteinaceous binders due to ultra violet (UV) radiation and possible interactions owing to the presence of historical mineral pigments. With this aim, three different paint model samples were prepared according to medieval recipes, using rabbit glue as proteinaceus binders. One of these model samples contained only the binder, and the other two were prepared by mixing each of the pigments (cinnabar or azurite) with the binder (glue tempera model samples). The model samples were studied by applying Principal Component Analysis (PCA) to their mass spectra obtained with Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF-MS). The complementary use of Fourier Transform Infrared Spectroscopy to study conformational changes of secondary structure of the proteinaceous binder is also proposed. Ageing effects on the model samples after up to 3000?h of UV irradiation were periodically analyzed by the proposed approach. PCA on MS data proved capable of identifying significant changes in the model samples, and the results suggested different aging behavior based on the pigment present. This research represents the first attempt to use this approach (PCA on MALDI-TOF-MS data) in the field of Cultural Heritage and demonstrates the potential benefits in the study of proteinaceous artistic materials for purposes of conservation and restoration.     

Subsurface analysis of painted sculptures and plasters using micrometre‐scale spatially offset Raman spectroscopy (micro‐SORS)

A recently developed variant of spatially offset Raman spectroscopy (SORS) for the non‐invasive analysis of thin painted layers, micro‐SORS, has been applied, for the first time, to real objects of Cultural Heritage – namely painted sculptures and plasters. Thin layers of paint originating from multiple restoration processes often applied over many centuries have been analysed non‐destructively using micro‐SORS to depths inaccessible to, or unresolvable into separate layers, by conventional confocal Raman microscopy. The concept has been demonstrated on several artistic artefacts of historical significance originating from Italy and dating from the medieval to the 18th century. The technique extends the depth applicability of Raman spectroscopy and with its inherently high chemical specificity that expands the portfolio of existing non‐destructive analytical tools in Cultural Heritage permitting to avoid cross‐sectional analysis often necessitated with this type of samples with conventional Raman microscopy. Currently, the method is non‐invasive only for artworks that can be placed under Raman microscope although there is a prospect for its use in a mobile system with largely removed restrictions on sample dimensions. © 2015 The Authors Journal of Raman Spectroscopy Published by John Wiley & Sons Ltd.     

The use of Raman microscopy and laser desorption ionization mass spectrometry in the examination of synthetic organic pigments in modern works of art

Synthetic organic pigments are widely used in modern and contemporary works of art. They have been examined by a variety of techniques including spectroscopic methods such as Fourier transform infrared spectroscopy, Raman, and X‐ray powder diffraction as well as chromatographic or mass spectrometric techniques such as pyrolysis‐gas chromatography/mass spectrometry and laser desorption ionization mass spectrometry (LDI–MS). Often, a combination of techniques has been used to examine these pigments. This paper describes use of Raman spectroscopy to create a database of colorants including two pigments not previously reported, PO1 and PO2. Then, using Raman spectroscopy in combination with LDI–MS, samples from modern works of art by artists including Mark Rothko, Barnett Newman, and José de Rivera were examined in order to identify the pigments present. One finding was that Rothko used a variety of red pigments over the course of his career including PR11 which has not been previously reported in artwork, and PO2 found with its positional isomer PR1. Knowledge of the colorants serves to inform conservators about display and treatment decisions. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

HERAS: A helium jet to prevent damage on works of art in Raman experiments

Raman spectroscopy is often used for non‐destructive analysis of works of art, polymers and biological materials, but in some cases, the laser beam can cause damages on the surface being studied due to the deposited beam energy. When possible, such damage can be prevented by minimizing laser intensity or acquisition time, but this is usually available only on high sensitivity bench‐top spectrometers. Portable Raman spectrometers are commonly not so flexible and an alternative is needed to ensure the safe study of sensitive works of art and other fragile materials. A helium jet aimed directly at the laser spot may prevent this damage from occurring and, in some cases, helps improving the Raman spectra. We designed a simple system (HERAS, Helium Raman System) consisting of a pinhole collimator, coupled to a helium line and a gas mass flux control and tested it on pyroxylin, vermilion and ochre paint references and pigment samples, using a 785 nm portable Raman spectrometer at various laser powers. Experimental conditions slightly differ for each sample, but small burns on the surface were avoided in all cases and only some ablation was observed on the most sensitive materials. The use of this coupled system allows the non‐destructive application of Raman to a wider variety of materials, while the technique remains portable. This setup may be used in bench‐top apparatus as well. Copyright © 2013 John Wiley & Sons, Ltd.     

Study of both fingerprint and high wavenumber Raman spectroscopy of pathological nasopharyngeal tissues

High wavenumber (HW) Raman spectroscopy has weaker fluorescence background compared with fingerprint (FP) region. This study aims to evaluate the discrimination feasibility of nasopharyngeal non‐cancerous and nasopharyngeal cancer (NPC) tissue with both FP and HW Raman spectroscopy. HW Raman spectra of nasopharyngeal tissue were obtained for the first time. Raman spectra were collected to differentiate nasopharyngeal non‐cancerous (n = 37) from NPC (n = 41) tissues in FP (800–1800cm⁻¹), HW (2700–3100cm⁻¹), and integrated FP/HW region. First, to assess the utility of this method, the averaged Raman spectral intensities and intensity ratios of corresponding Raman bands were analyzed in HW and FP regions, respectively. The results show that intensities as well as the ratios of specific Raman peaks might be helpful in distinguishing nasopharyngeal non‐cancerous from NPC tissue with the HW Raman spectroscopy, as with FP Raman reported before. The multivariate statistical method based on the combination of principal component analysis–liner discriminant analysis (PCA‐LDA), together with leave‐one‐patient‐out, cross‐validation diagnostic algorithm, was used for discriminating nasopharyngeal non‐cancerous from NPC tissue, generating sensitivities of 87.8%, 85.4%, and 95.1% and specificities of 86.5%, 91.9%, and 89.2%, respectively, with Raman spectroscopy in the FP, HW, and integrated FP/HW regions. The posterior probability of classification results and receiver operating characteristic curves were utilized to evaluate the discrimination of PCA‐LDA algorithm, verifying that HW Raman spectroscopy has a positive effect on the differentiation for the diagnosis of NPC tissue by integrated FP/HW Raman spectroscopy. What's more, the potential of Raman spectroscopy used for differentiating different pathology NPC tissues was also discussed. The results demonstrate that both FP and HW Raman spectroscopy have the potential for diagnosis and detection in early nasopharyngeal carcinoma, and HW Raman spectroscopy may improve the discrimination of NPC tissue compared with FP region alone, providing a promising diagnostic tool for the diagnosis of NPC tissue. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of mural paintings using in situ non‐invasive XRF,FTIR spectroscopy and optical microscopy

An analytical protocol consisting of X‐ray fluorescence spectroscopy, optical microscopy and Fourier transform infrared spectroscopy was used to study the origin and the nature of the materials (pigments, binders and coating preparation) of the Fundenii Doamnei church mural paint from Bucharest. The main interest of the present study consisted in the original votive paint from narthex, painted in 1757 in a secco technique. During analysis, an unexpected pigment in the votive paint could be detected by the combined analytical techniques: ultramarine blue. Along with this pigment, the presence of gypsum binder based on egg and flax seed oil could also be evidenced. These results demonstrated a secco execution technique of the votive paint and also the presence of a restoration treatment. Moreover, during the present study, the components of the preparation layer and the constitutive pigments from both 1699 and 1757 years mural paints have been analyzed. Hence, the following pigments could be identified: vermilion, azurite, cinnabar, lead white, ochre, natural umber and gold, by using the combination of the analytical techniques. The novelty of our results consists in detecting the composition of the materials used in this church painting (fresco and a secco) during these 254 years since its first restoration. The results of these investigations pointed to the suitability of the non‐destructive and semi‐destructive analytical techniques in the complex characterization of the paints realized in different techniques, at different periods. Copyright © 2013 John Wiley & Sons, Ltd.     

Rapid screening of sildenafil and tadalafil adulterated in healthcare products by Micro‐Raman spectroscopy

Sildenafil and tadalafil are inhibitors of phosphodiesterase type 5, which are frequently added into healthcare products. The objective of this study was to evaluate the possibility of using micro‐Raman spectroscopy as a non‐destructive technique to screen for sildenafil and tadalafil in adulterated healthcare products. Using a viewing microscope, the suspect area of healthcare products was selected, which had a discernable crystal form or shape from the surrounding zone. Optimization of instrumental parameters of the Raman spectrometer was chosen to reduce the background fluorescence, and the Raman spectra were collected. The spectra collected were compared with the standard Raman spectra of pure sildenafil and tadalafil. Samples with an identifiable Raman signature to that of sildenafil or tadalafil could be confirmed using liquid chromatography–mass spectrometry (LC/MS). Additionally, wavelet denoising combined with similarity calculation was used to establish an automated approach for discrimination of adulterated healthcare products. Correlation coefficient was chosen for similarity calculation based on the spectra collected and the standard Raman spectra of pure sildenafil and tadalafil. We compared ten samples, secured by administrative authorities in Shanghai, to analyse and demonstrate the capabilities of our proposed method. We established six samples containing sildenafil or tadalafil warranting analysis using LC/MS. Thus, the use of micro Raman spectroscopy provides a quick, convenient and non‐destructive method for screening adulterated chemicals in healthcare products. Raman spectroscopy combined with similarity calculation requires little training after spectra library is developed, thus showing great promise to identify the adulterated healthcare products in the future. Copyright © 2012 John Wiley & Sons, Ltd.     

Raman microscopy of prehistoric paintings in French megalithic monuments

Remains of pictorial decorations in a series of six representative megalithic monuments of Brittany (France) and two French stelae have been studied by micro‐Raman spectroscopy for the first time. Fungal colonies on the painted orthostats made it difficult to obtain in situ Raman spectra of the paint components. Nevertheless, paint micro‐specimens studied in the laboratory by micro‐Raman spectroscopy, X‐ray photoelectron spectroscopy and scanning electronic microscopy combined with energy dispersive X‐ray spectroscopy have made possible to characterise the materials present. The minerals α‐quartz, albite, microcline, muscovite, phlogopite, celadonite, beryl and anatase have been identified in the granitic rocks supporting the paintings, while dolomite and calcite are dominant in the calcareous rocky substrata. Haematite is the main component of the red pictographs, whereas amorphous carbon and manganese oxides/oxihydroxides have been used in the black ones. Calcite, gypsum and amorphous carbon have been detected as additional components of the paint in some cases. Contamination with modern tracing materials (polystyrene and ε‐copper‐phthalocyanine blue) has been detected in several cases. The presence of pigments as decorative elements in megalithic monuments of Western France and its possible relation with those of the Iberian Peninsula create interesting expectations for the knowledge of the European megalithic culture. Copyright © 2015 John Wiley & Sons, Ltd.