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Microspatially offset Raman spectroscopy (micro-SORS) has been proposed as a valuable approach to sample molecular information from layers that are covered by a turbid (nontransparent) layer. However, when large magnifications are involved, the approach is not straightforward, as spatial constraints exist to position the laser beam and the objective lens with the external beam delivery or, with internal beam delivery, the maximum spatial offset achievable is restricted. To overcome these limitations, we propose here a prototype of a new micro-SORS sensor, which uses bare glass fibers to transfer the laser radiation to the sample and to collect the Raman signal from a spatially offset zone to the Raman spectrometer. The concept also renders itself amenable to remote delivery and to the miniaturization of the probe head which could be beneficial for special applications, e.g., where access to sample areas is restricted. The basic applicability of this approach was demonstrated by studying several layered structure systems. Apart from proving the feasibility of the technique, also, practical aspects of the use of the prototype sensor are discussed.

In the framework of the inter-disciplinary KongoKing project, a set of beads from archaeological excavations in the Democratic Republic of the Congo was analysed by means of a minimally invasive, multi-analytical approach based on micro-Raman spectroscopy. The full characterization of the materials, including glassy network, opacifiers and colorizers, was achieved thanks to the combination of data from handheld X-ray fluorescence, variable pressure scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, micro-Fourier transform infrared spectroscopy and pyrolysis coupled to gas chromatography and mass spectrometry. The obtained chemical information was used to fill the existing gap in the chemical study of beads from Western Central Africa. The cobalt-rich blue beads were found to be of Central European origin, while the copper-rich turquoise beads were manufactured using distinct copper sources. Cadmium yellow and cadmium red are the colourants responsible for the bright colours of bead types 10 and 12, respectively. The type 12 beads were found to be composed of glass covered with a waxy layer tentatively identified as Japan wax. Prosser-moulded bead type 9 was coloured by means of a chrome–tin pigment, while a combination of Mn and Fe is responsible for the black colour of the type 47 beads. Cuprite is most likely responsible for the red hue of glass layers from type 14. The dark palm green exterior of the type 17 bead was produced by using a combination of Cu and Fe compounds; iron was the only chromophore detected in the Indian red decoration. Copyright © 2017 John Wiley & Sons, Ltd.

An extensive in situ Raman spectroscopic campaign was performed on archaeological sites in three different provinces in Patagonia, Argentina (Neuquén, Río Negro and Chubut). 16 open air shelters located in different environments (forests, ecotones, steppes) were investigated and interpreted in terms of pigments used and the identification of substrata. Special attention was given to the alteration products and accretions that were found on the rock art paintings of the shelters and on the surface of the rock walls, as they can affect and damage this magnificent works of art. Haematite (α-Fe2O3) was the main chromophore that was found on the red paintings of the most of the shelters studied. The green earth glauconite, was identified only in one case, by using a red (785 nm) and a green laser (532 nm). Other minerals and silicates were found on the coloured areas but also on the rock support. Calcite (CaCO3) and gypsum (CaSO4 • 2H2O) crystallization was identified on the paintings, crusts and rock surfaces, in combination or alone, and are associated with weathering. In some cases the shelters were so severely degraded that no Raman signal of pigments and/or other components could be retrieved. Calcium oxalates were also detected in several figures and motifs in different shelters. Fil: Rousaki, Anastasia. University of Ghent; Bélgica Fil: Vargas, Fernando Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Diversidad Cultural y Procesos de Cambio. Universidad Nacional de Río Negro. Instituto de Investigaciones en Diversidad Cultural y Procesos de Cambio; Argentina Fil: Vázquez, Cristina. Comisión Nacional de Energía Atómica; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; Argentina Fil: Aldazabal, Veronica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Multidisciplinario de Historia y Ciencias Humanas; Argentina Fil: Bellelli, Cristina Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Secretaría de Cultura de la Nación. Dirección Nacional de Cultura y Museos. Instituto Nacional de Antropología y Pensamiento Latinoamericano; Argentina Fil: Carballido Calatayud, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Secretaría de Cultura de la Nación. Dirección Nacional de Cultura y Museos. Instituto Nacional de Antropología y Pensamiento Latinoamericano; Argentina. Universidad de Buenos Aires; Argentina Fil: Hajduk, Adam. Administración de Parques Nacionales. Museo de la Patagonia "Francisco Perito Moreno"; Argentina Fil: Palacios, Oscar Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; Argentina Fil: Moens, Luc. University of Ghent; Bélgica Fil: Vandenabeele, Peter. University of Ghent; Bélgica

Raman spectroscopy is a powerful technique for the characterization of materials and is of valuable use in archaeometrical research in general. Green compounds of natural or synthetic origin are found in many research areas, ranging from mineralogy, to pigment identification, to corrosion studies. However, a detailed and comprehensive database of spectra and references is still missing in the literature. This paper provides both, a literature review and downloadable Raman spectra of reference products, to the researcher dealing with green materials in cultural heritage. Moreover, it tackles nomenclature issues. The collected spectra are discussed in relation to the preliminary/commercial identification of the material itself and to the published data. Practical aspects regarding the laser wavelength selection are also discussed with regards to the comparison to published reference spectra. The range of studied green materials is wide and encompasses Cu containing compounds (natural and synthetic, more or less known as pigments or degradation products, including polymorphs of the same formula), Fe based (green earths and synthetic organic pigments), modern Cr and Co green pigments. This approach is illustrated by analysing a cross section of a green zone of the Early Netherlandish panel painting ‘Ghent Altarpiece’ by the Van Eyck brothers. Copyright © 2016 John Wiley & Sons, Ltd.

Archaeometry is the research area on the edge between humanities and natural sciences: it uses and optimises methods from chemistry, spectroscopy, physics, biology, etc. to help answering research questions from humanities. In general, these objects are investigated for several reasons. Besides the fundamental interest to know about the materials that were used in the past, the study of artefacts can support their preservation, either by helping to select optimal storage or display conditions, either by investigating decay pathways and suggesting solutions. Other reasons for art analysis include provenance studies, dating the artefact or identifying forgeries. Since several years, Raman spectroscopy is increasingly applied for the investigation of objects of art or archaeology. The technique is well-appreciated for the limited (or even absent) sample preparation, the relative straightforward interpretation of the spectra (by fingerprinting - comparing them against a database of reference pigments) and its speed of analysis. Moreover, the small spectral footprint – allowing to record a molecular spectrum of particles down to 1 µm, the typical size of pigment grains – is certainly a positive property of the technique. Raman spectroscopy can be considered as rather versatile, as inorganic as well as organic materials can be studied, and as the technique can gather information on crystalline as well as on non-crystalline phases. As a consequence, Raman spectroscopy can be used to study antique objects and twentieth-century synthetic (organic) materials – illustrating the wide range of applications. Finally, the technique is as non-destructive, provided the laser power is kept sufficiently low not to damage the artwork. In literature, the terms “non-invasive” and “non-destructive” are used, where the first term means that no sampling is involved, and the latter term indicates that no sample is taken or that during analysis the sample is not consumed (destroyed) and remains available for further analysis.

Pigments and colourants are materials that have an enormous impact on how artworks are appreciated. Therefore, it is no surprise that since the first applications of Raman spectroscopy in art analysis, the study of this group of materials has gained special attention. Whereas the first applications often involved the identification of (mostly inorganic) pigments, the field has broadened towards the analysis of organic materials, such as synthetic pigments. Moreover, the study of dyes has gained from the developments in surface-enhanced Raman spectroscopy (SERS). Moreover, recently micro-spatially offset Raman spectroscopy (micro-SORS) was developed as a promising technique to study layered structures, such as paint layers.

Raman spectroscopic studies of carbonaceous materials are, until now, mainly devoted to geological and industrial materials. On the other hand, it is known from artistic literature that many varieties of carbon-based black pigments were produced and used in different places and times, and according to the artist’s preferences. The ability of Raman spectroscopy to analyse particles down to 1 μm and its non-destructiveness make it an ideal tool for pigments investigation. Anyway, the discrimination among different types of carbon-based black pigments is affected by various aspects, one of which is the lack of reference spectra as well as of specific nomenclature. In this paper, reference materials have been studied by means of Raman spectroscopy to provide reference spectra. All the pigments showed two broad bands of carbon, but sometimes specific excitation conditions were required to record a good quality Raman spectrum. The obtained Raman signatures are discussed, on the basis of the specificities of the pigment (natural or artificial origin; structural implications related to the raw materials used or to production processes; etc.). Therefore, on the basis of the Raman spectra of painting materials, further knowledge can be obtained on the type of carbon-based black pigments in works of art. Copyright © 2015 John Wiley &S ons, Ltd.

Direct identification of pigments in mediaeval illuminated manuscripts was one of the first applications of Raman spectroscopy in art and archaeology. In previous in situ analysis of handwritings, the equipment was typically provided with a single excitation source. In this work, a portable Raman spectrometer (EZRAMAN-I-DUAL Raman system) is introduced to characterise the pigments used in an important illuminated mediaeval manuscript, De Civitate Dei (Library in Bruges, Ms.106). Characteristics important for these in situ measurements were discussed. We introduce a set-up that allows stable positioning of the equipment and point out the advantage of the availability of two lasers, which are part of the instrument. Good performance of the introduced Raman spectrometer, to allow pigment identification in a short time, is proved. Finally, pigments such as lead white (2PbCO3 · Pb(OH)2), lead–tin yellow type I (Pb2SnO4), malachite (Cu2CO3(OH)2), mosaic gold (SnS2), vermillion (HgS), carbon black (C), red lead (Pb3O4) and azurite (Cu3(CO3)2(OH)2) could be identified. These pigments were often used in mediaeval artworks and contribute to the enrichment of information of the materials used by the illuminator. Copyright © 2014 John Wiley & Sons, Ltd.

During the last decades, Raman spectroscopy has grown to an established analytical technique in archaeometry, art analysis and conservation science. Mobile Raman instruments were designed to be used for in situ characterisation and identification of inorganic and organic materials in art and archaeometry. This research paper aims to point out several aspects that need to be considered when selecting a mobile Raman spectrometer for in situ archaeometrical studies. We describe an approach to evaluate these parameters and apply this to a dual laser portable Raman spectrometer. Twofold characterisation of mobile Raman instrumentation for art analysis: (i) investigation of spectroscopic characteristics such as (amongst others) spectral resolution, spectral window, signal to noise ratio and limit of detection; (ii) evaluation of specific properties that are useful for mobile studies in archaeometry. These include options for easy positioning and focussing, the ability to reduce laser power on the surface of the art object and the working distance between the probehead and the artefact. Finally, the research was completed with field tests by studying the pigments of a mediaeval wall painting.

Because of its major contributions to the world economy and cultural heritage, Chinese porcelain and its technology can be considered as very important. In this research, the applicability of Raman spectroscopy and X-Ray Fluorescence (XRF) spectroscopy to study the pigments of the ruan-cai colour palette of Chinese porcelain dating from the 18th century was evaluated. Next to the investigations based on stylistic analysis, the use of other analysis techniques is important to obtain complementary information. Raman spectroscopy and XRF spectroscopy are two non-invasive, analytical techniques proven to be useful for the determination of the nature and composition of pigments used to decorate ceramics. As a result, analytical analysis allows us to retrieve more information about the production of Chinese porcelain. Based on visual inspection of the decoration, the objects could be divided into two groups and to evaluate the use of the combined analytical approach, all groups and subgroups were sampled. Before Raman and XRF analyses, the samples were cut, embedded and polished, in order to be able to measure the transversal section of the samples. In this way, each layer of the porcelain samples could be analysed separately. The results show that the blue colour is cobalt-aluminium oxide, in red zones haematite (α-Fe2O3) is present and the green area contains a mixture of CuO in a lead-rich basis and a solid solution of malachite (Cu2CO3(OH)2). The opaque yellow and white colours were identified as lead tin yellow type II (PbSn1−xSixO3, where x ∼ 0.25) and a lead arsenate, respectively.

In art analysis, copper phthalocyanine (CuPc) is often identified as an important pigment (PB15) in 20th century artworks. Raman spectroscopy is a very valuable technique for the detection of this pigment in paint systems. However, PB15 is used in different polymorphic forms and identification of the polymorph could retrieve information on the production process of the pigment at the moment. Raman spectroscopy, being a molecular spectroscopic method of analysis, is able to discriminate between polymorphs of crystals. However, in the case of PB15, spectral interpretation is not straightforward, and Raman data treatment requires some improvements concerning the PB15 polymorphic discrimination in paints. Here, Raman spectroscopy is combined with chemometrical analysis in order to develop a procedure allowing us to identify the PB15 crystalline structure in painted layers and in artworks. The results obtained by Linear Discriminant Analysis (LDA), using intensity ratios as variables, demonstrate the ability of this procedure to predict the crystalline structure of a PB15 pigment in unknown paint samples.

The combined use of handheld energy-dispersive X-ray fluorescence spectrometry, Raman spectroscopy, and micro-energy-dispersive X-ray fluorescence spectrometry permitted the characterization of Roman glass tesserae excavation from the Coriglia (Italy) archeological site. Analyses of ten different glass colors were conducted as spot analyses on intact samples and as both spot analyses and line scans on select cross-sectioned samples. The elemental and molecular information gained from these spectral measurements allowed for the qualitative chemical characterization of the bulk glass, decolorants, opacifiers, and coloring agents. The use of an antimony opacifier in many of the samples supports the late Imperial phasing as determined through numismatic, fresco, ceramics, and architectural evidence. And dealinization of the exterior glass layers caused by the burial environment was confirmed.

In archaeometry, the advantages of a combined use of Raman spectroscopy and X-ray fluorescence spectroscopy are extensively discussed for applications such as the analysis of paintings, manuscripts, pottery, etc. Here, we demonstrate for the first time the advantage of using both techniques for analysing glyptics. These engraved gemstones or glass materials were originally used as stamps, to identify the owner, for instance on letters, but also on wine vessels. For this research, a set of 64 glyptics (42 Roman glass specimens and 22 modern ones), belonging to the collection of the museum 'Quinta das Cruzes' in Funchal (Madeira, Portugal), was analysed with portable Raman spectroscopy and handheld X-ray fluorescence (hXRF). These techniques were also used to confirm the gemological identification of these precious objects and can give extra information about the glass composition. Raman spectroscopy identifies the molecular composition as well as on the crystalline phases present. On the other hand, hXRF results show that the antique Roman glass samples are characterised with low Pb and Sn levels and that the modern specimens can be discriminated in two groups: lead-based and non-lead-based ones.

A selection of illuminations of the 12th century manuscript Liber Floridus was analysed with Raman spectroscopy (in situ and laboratory measurements), X-ray fluorescence spectroscopy, UV-fluorescence photography and infrared reflectography (IRR). The aim of this study is to determine the pigments used, in order to search for anachronisms. Using a combination of Raman spectroscopy (molecular information) and X-ray fluorescence spectroscopy (elemental information) following pigments could be identified: ultramarine (Na(8-10)Al(6)Si(6)O(24)S(2-4)), azurite (2CuCO(3)·Cu(OH)(2)), caput mortuum (Fe(2)O(3)), vermilion (HgS), orpiment (As(2)S(3)) and lead white (2PbCO(3)·Pb(OH)(2)). Moreover, two synthetic red pigments, PR4 and PR176, and a degradation product, gypsum (CaSO(4)·2H(2)O), were present in the manuscript. To establish the origin of the modern materials UV-fluorescence photography was used. Infrared reflectography (IRR) was applied to visualise the underdrawing of the investigated folios.

In this paper, Raman spectroscopy is used for the first time to identify the pigments on decorated antique Iberian pottery. Ceramic fragments of type Real and others from the archaeological excavation in the oppidum Puente Tablas were examined. Different types of iron oxide pigments (hematite and goethite) were identified, along with amorphous carbon. In some samples, the presence of chalk or gypsum could be demonstrated. Some unattributed Raman bands are believed to be associated either with post-burial organic deposition or with silicate materials that are present in red ochre. It was possible to relate the findings with geological data from the region and to make assumptions on a local production. Copyright © 2009 John Wiley & Sons, Ltd.

In this study, the effect of low-shear microgravity on the metabolism of Cupriavidus metallidurans LMG 1195 was studied with Raman spectroscopy. Therefore, the strain was cultured for 24 or 48 h in a rotating wall vessel to simulate microgravity (SMG) and in a control setup. The differences in Raman spectra recorded from both setups after 24 h of culturing were small. The most prominent features in a difference spectrum, calculated between the mean spectra from the microgravity and the control setup separately, could be assigned to the presence of poly-β-hydroxybutyrate (PHB). SMG seems to yield a higher PHB production after 24 h of culturing. Additional processing of the spectra suggested that SMG induced also other changes in the carbon-metabolism. After 48 h, similar results were found for the carbon metabolism, while PHB concentrations were reduced in SMG compared to the control. However, these differences could also be caused by interfering effects that may occur in the bioreactors after a prolonged incubation time.

This study explored the potential of Raman spectroscopy for the analysis of poly(3-hydroxybutyrate) (PHB) in bacteria. PHB can be formed in large amounts by certain bacteria as a storage material and is of high importance for industrial biodegradable plastic production. Raman spectra were collected from Cupriavidus necator DSM 428 (H16), from its non-PHB-producing mutant strain C. necator DSM 541, and from pure PHB, in order to determine at which Raman shifts a contribution of PHB in bacterial spectra can be expected. The Raman band intensity at ca. 1734 cm(-1) appeared to be suitable for the monitoring of PHB production and consumption. These intensities were linearly related to the PHB concentration (mg L(-1) culture) determined by parallel HPLC analysis. Therefore, Raman spectroscopy is considered as a fast and noninvasive technique for the determination and monitoring of the PHB content in bacteria.

In this paper we explore the possibilities of Raman spectroscopy in order to deduce information on the fatty acid composition of bacterial cells. Therefore, representative strains of two bacterial taxa were each cultured in different conditions and in parallel analyzed by Raman spectroscopy and gaschromatographic FAME analysis. Raman spectra of pure fatty acids were recorded and used as reference spectra. The culturing conditions for each strain could be easily distinguished by the fatty acid information retrieved from bacterial Raman spectra. Chemometric techniques such as EMSC and PCA allowed to extract information about groups of fatty acids, that was consistent with the results from FAME analysis. Although the information retrieved from Raman spectroscopy is not as refined as that from FAME analysis, the presented methods could be useful to obtain basic information on the fatty acid present in bacteria when performing Raman spectroscopic analysis for fast whole cell profiling, which provides information for different types of cell components (fatty acids, amino acids, primary metabolites, etc.).

We hereby report on the design of a set-up combining micro-resonance Raman and absorption spectroscopy with a microfluidic system. The set-up enabled us to study the nerve globin of Aphrodite aculeata in the functional isolated nerve cord under varying physiological conditions for extended periods of time. The oxygenation cycle of the organism was triggered by utilizing the microfluidic system that allowed for a fast switch between aerobic and anaerobic conditions. The nerve globin was found to very easily shift from a penta-coordinated high spin ferrous form to the oxy state upon a change from anaerobic to aerobic conditions. The observed fast reaction to varying O2 concentrations supports an oxygencarrying and/or -storing function of the nerve globin. In addition, by combining resonance Raman and absorption spectroscopy, the physiological response could be distinguished from light-induced effects. © 2007 Elsevier B.V. All rights reserved.

Raman spectroscopy has been applied to the examination of wall painting fragments from the archaeological site of Ek'Balam (Yucatán, Mexico). Thirty-three samples have been studied, all originating from room 23 of the Acropolis, and being representative of the painting technique at Ek'Balam during the late Classic Maya period. Several pigments such as haematite, calcite, carbon, cinnabar and indigo were identified in these samples. The latter pigment was presumed to be present as 'Maya blue', which is an intercalation product of indigo and palygorskite clay. The observed Raman spectra are reported and some band assignments have been made. This survey is the first Raman spectroscopic examination of a whole set of pigments in archaeological Maya wall painting fragments.

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.

The analysis of precious artefacts and antiquities demands care in order to minimise the risk of accidental damage during measurement. Mobile fibre-optic-based Raman instruments offer a means to avoid destructive sampling and eliminate the need to transport artefacts for spectrochemical analysis. In this work we present a new mobile instrument developed and optimised for the in situ Raman investigation of objects of art and antiquities. The instrument is controlled by a portable computer. Selected mounts cover many types of artefacts. Newly written software routines organise spectra together with measurement parameters and facilitate calibration of the instrument. The present paper describes this new Raman instrument and discusses some challenges in the transition from a laboratory environment to in situ investigations in museums.

Confocal micro-Raman spectroscopy requires a minimum of sample handling and no reagents and allows fast identification of microorganisms. Since it reflects the overall molecular composition of the cells, it provides much more information than classical, microbial analyses. However, since the molecular makeup of a cell depends on culture conditions, it can be argued that this will affect the reproducibility and discrimination ability of Raman spectroscopy. We used Bacillus cereus, Bacillus pumilus, and Bacillus licheniformis, which are known to be clearly distinct from each other and each displaying important phenotypic heterogeneity, in a wide variety of culture conditions to analyze this. It is illustrated that the influence of culture conditions on the identification accuracy and taxonomic resolution of Raman spectroscopy is important though the effect on the final identification is limited within the set of stains studied. Furthermore, some conditions even allow for better discrimination than others. From a practical point of view, it is especially important that differences in culturing time (and culturing temperature) can be accommodated.

Dispersive Raman spectra of six copal resins, that were purchased in local markets in Mexico, are presented. The spectra were interpreted and compared with each other. For all these spectra, the relative intensity of the Raman band at approximately 1645 cm −1 , attributed to the exomethylene ν (CC) stretching vibration, was rather low, especially as fresh samples are involved. In one resin, viz. Incienso , CaCO 3 was detected. Probably this inorganic pigment was added as a whitener. In the spectrum of Lagrima a starch fraction was present. Raman spectra of a sample from an Aztec figurine were recorded. It was shown that its composition was inhomogeneous at the micrometer level. Here, too, CaCO 3 was observed. It was not possible to identify the resin applied in the antique figurine due to material degradation by age and environmental exposure.

The characterization of artists' materials is of great importance for the conservation and restoration of 20th century paintings, and it provides information which is of art-historical interest. The identification of modern organic pigments by Raman spectroscopy is hampered by the large amount of different synthetic materials that exist. Therefore, an extended database of reference spectra is needed. Besides this spectral library, there is need for an accurate and fast-searching algorithm for selecting the reference spectrum that best corresponds with the unknown spectrum. A principal components-based spectral searching algorithm is proposed that largely reduces the number of data points for each spectrum. By subsequent measurement of the Euclidian distance between the unknown and the reference spectra in the principal components space, the corresponding reference can be selected. The algorithm is tested by using the results of the Raman spectroscopic analysis of different colored pencils. Different qualities of matches for the identification protocol could be distinguished. The synthetic organic pigments in micro-samples of the painting “Faubourg” by Paul Delvaux could be identified by the proposed algorithm.

Raman spectroscopy has grown to be one of the techniques of interest for the investigation of art objects. The approach has several advantageous properties, and the non-destructive character of the technique allowed it to be used for in situ investigations. However, compared with laboratory approaches, it would be useful to take advantage of the small spectral footprint of the technique, and use Raman spectroscopy to study the spatial distribution of different compounds. In this work, an in situ Raman mapping system is developed to be able to relate chemical information with its spatial distribution. Challenges for the development are discussed, including the need for stable positioning and proper data treatment. To avoid focusing problems, nineteenth century porcelain cards are used to test the system. This work focuses mainly on the post-processing of the large dataset which consists of four steps: (i) importing the data into the software; (ii) visualization of the dataset; (iii) extraction of the variables; and (iv) creation of a Raman image. It is shown that despite the challenging task of the development of the full in situ Raman mapping system, the first steps are very promising. This article is part of the themed issue ‘Raman spectroscopy in art and archaeology’.

The application of Raman spectroscopy to the examination of ancient art and the identification of mineral pigments used in antiquity has been demonstrated successfully hitherto. However, the examination of modern objects of art is hampered by the absence of a spectral library database of relatively modern organic pigments and dyestuffs, of which there are a large number. Azo pigments provide an example historically of a class of synthetic organic pigments which have been adopted by artists. The Raman spectra of 21 azo pigments were analysed and a protocol was established for their identification. Using this database, two azo pigments from 1 µg samples of 20th century paintings attributed to Picasso and Appel were characterized. Copyright © 2000 John Wiley & Sons, Ltd.

Raman spectroscopy and X-ray fluorescence (XRF) spectroscopy are often used as complementary techniques that are well suited for the analysis of art objects because both techniques are fast, sensitive, and noninvasive and measurements can take place in situ. In most of these studies, both techniques are used separately, in the sense that the spectra are evaluated independently and single conclusions are obtained, considering both results. This paper presents a data fusion procedure for Raman and XRF data for the characterization of pigments used in porcelain cards. For the classification of the analyzed points of the porcelain cards principal component analysis (PCA) was used. A first attempt was made to develop a new procedure for the identification of the pigments using a database containing the fused Raman-XRF data of 24 reference pigments. The results show that the classification based on the fused Raman-XRF data is significantly better than the classifications based on the Raman data or the XRF data separately. © 2011 Society for Applied Spectroscopy.

Raman spectroscopy, being a laser spectroscopic method, is gaining increasingly more interest for applications in the field of art and archaeology. The technique is especially appreciated for its non-destructive character, the speed of analysis and the ability to obtain molecular information on a whole range of materials, organic as well as inorganic. Although the Raman effect was observed for the first time in 1928, it was not until the end of the 1980s before instrumental improvements enabled the analysis of micro-samples, and thus allowing the application of this method in archaeometry. Next to the identification of inorganic materials, organic matter, such as resins and binders, has often been examined by using Raman spectroscopy. Together with the comparison to reference spectra, spectral interpretation is often involved to attribute the Raman bands to specific molecular vibrations. This is mainly of importance when studying archaeological materials that have suffered degradation over time. Recently fibre optics instrumentation became available for the direct and non-destructive analysis of artefacts. Although the approach seems simple and easy to apply, there are several drawbacks that need our attention. For instance, due to the different nature of a mediaeval manuscript, mediaeval wall paintings on the vault of a chapel, panel paintings and polychrome sculptures, different experimental set-ups are needed to deal with the diversity of artefacts. Moreover, these set-ups need to guarantee sufficient stability to allow focusing of the laser beam on the artefact.

During the last few years, counterfeiters have become increasingly sophisticated by falsifying drugs and making them look identical to genuine tablets. In this paper, Raman spectroscopy is proposed as a fast and reliable method for the detection of counterfeit Viagra tablets. This technique can easily differentiate genuine from counterfeit tablets without the need of sample preparation. In total 18 tablets were analysed which all contained the active ingredient sildenafil, but different excipients were used, as could be observed in the Raman spectra between 1150 and 700 cm(-1). So, the spectra could be divided into genuine or counterfeit. Additionally, principal component analysis (PCA), combined with hierarchical cluster analysis (HCA), was used to establish an automated approach for the discrimination of counterfeit from genuine Viagra tablets. Raman spectroscopy, combined with principal components analysis, could be used in the future by customs or in the field to identify counterfeit tablets on the spot without involvement of trained chemists.

Endospores and endospore-forming bacteria were studied by Raman spectroscopy. Raman spectra were recorded from Bacillus licheniformis LMG 7634 at different steps during growth and spore formation, and from spore suspensions obtained from diverse Bacillus and Paenibacillus strains cultured in different conditions (growth media, temperature, peroxide treatment). Raman bands of calcium dipicolinate and amino acids such as phenylalanine and tyrosine are more intense in the spectra of sporulating bacteria compared with those of bacteria from earlier phases of growth. Raman spectroscopy can thus be used to detect sporulation of cells by a characteristic band at 1,018 cm(-1) from calcium dipicolinate. The increase in amino acids could possibly be explained by the formation of small acid-soluble proteins that saturate the endospore DNA. Large variations in Raman spectra of endospore suspensions of different strains or different culturing conditions were observed. Next to calcium dipicolinate, tyrosine and phenylalanine, band differences at 527 and 638 cm(-1) were observed in the spectra of some of the B. sporothermodurans spore suspensions. These bands were assigned to the incorporation of cysteine residues in spore coat proteins. In conclusion, Raman spectroscopy is a fast technique to provide useful information about several spore components.

the applicationof this technique in this field has grown exponentially.Although this database and the papers from several groupsthat appeared around the same time introduced many peopleto this research field, these were not the first applications ofRaman microspectroscopy in art analysis. In 1979 Dhamelin-court et al.

During the last decade there has been an apparent increase in the prevalence of counterfeit medicines in developing as well as developed countries. The pivotal antimalarial artesunate has been counterfeited on a large scale in SE Asia. In this work, the possibilities of Raman spectroscopy are explored as a fast and reliable screening method for the detection of counterfeit artesunate tablets. In this study, 50 'artesunate tablets', purchased in SE Asia, were examined. This spectroscopic method was able to distinguish between genuine and counterfeit artesunate and to identify the composition of the counterfeit tablets. These contained no detectable levels of artesunate, but consisted mostly of starch, calcite (CaCO3), and paracetamol (4-acetamidophenol). In one particular case an admixture of rutile (TiO2) and artesunate was detected. The results of the investigation by Raman spectroscopy were in agreement with those of colorimetric tests and of liquid chromatography-mass spectrometry on the artesunate. Moreover, principal components analysis (PCA) was combined with hierarchical cluster analysis to establish an automated approach for the discrimination between different groups of counterfeits and genuine artesunate tablets. These results demonstrate that Raman spectroscopy combined with multivariate analysis is a promising and reliable methodology for the fast characterization of genuine and counterfeit artesunate antimalarial tablets. Copyright © 2006 John Wiley and Sons, Ltd.

In archaeometry, one of the main concerns is to extract information from an art object, without damaging it. Raman spectroscopy is being applied in this research field with recent developments in mobile instrumentation facilitating more routine analysis. This research paper evaluates the performances of five mobile Raman instruments (Renishaw RA100, Renishaw Portable Raman Analyser RX210, Ocean Optics RSL-1, Delta Nu Inspector Raman, Mobile Art Analyser - MArtA) in three different laboratories. A set of samples were collected, in order to obtain information on the spectral performances of the instruments including: spectral resolution, calibration, laser cut-off, the ability to record spectra of organic and inorganic pigments through varnish layers and on the possibilities to identify biomaterials. Spectra were recorded from predefined regions on a canvas painting to simulate the investigation of artworks and the capabilities to record spectra from hardly accessible areas was evaluated.

Confocal Raman spectroscopy is a non-destructive analytical method which is useful to obtain detailed information about the molecular composition of biological samples. Its high spatial resolution was used to collect spectra of single basidiospores of macrofungi of the genera Collybia, Gymnopus, Laccaria, Lactarius, Mycena and Russula. These spectra can be divided into three major taxon-related groups, with general compositional differences, such as the relative amount of lipids compared to proteins. In this study, collapsing of thin-walled spores during storage was often observed, a phenomenon which has been given little attention in the literature. The Raman spectra are treated with different chemometric preprocessing techniques, including Savitsky-Golay, standard normal variate (SNV) preprocessing and extended multiplicative scatter correction (EMSC). By using linear discriminant analysis, approximately 90% of the spectra can be assigned to the correct genus, but identification on the species level was not possible.

This work represents the Raman spectra of 15 natural artists’ materials that were obtained from local market in Mexico. Some of these products are not endemic to the region, but are often used in local conservation practice. Other materials are of local origin and have been used for centuries by local craftsmen. The Raman spectra that are reported here are: Chia oil, linseed oil, Campeche wax, beeswax, white copal, dammar, colophony, mastic, pixoy, chapopote, chucum, aje gum, gutta gum, peach gum and gum Arabic. The sample of pixoy was mixed with TiO2, although it was not clear whether this was done intentionally or not. The Raman spectrum of chapopote, the local name for bitumen, contained features of carbonaceous and terpenoid matter. The Raman spectra of chapopote and chucum suffered severely from fluorescence, resulting in noisy Raman spectra. Aje gum and gutta gum are not gums, since they are resinous (terpenoid) in nature. Aje is a rare animal resin originating from Coccus axin.

In this study, we explore Raman spectra of bacteria for their biochemical information. Therefore, a database of biomolecules was used and several approaches were applied such as the study of difference spectra, the calculation dot products, the usage of coefficients obtained from an EMSC procedure and the application of 2D correlation spectroscopy. These methods were applied on a dataset containing Raman spectra of Cupriavidus metallidurans LMG 1195 in five stages of its growth, aiming to extract information about the evolution of cell components during growth. EMSC coefficients seemed to be most promising for tracking metabolic products and the results were often confirmed by difference spectra or by 2D correlation spectroscopy.

Lactarius is a genus of Basidiomycotina with mainly agaricoid representatives, which are characterised by the excretion of a typical milky fluid. In particular, the colour, changes and taste of this latex-like milk are often used as a taxonomically important character. When it is exuded several chemical reactions occur. To date, NMR spectroscopy is generally used for chemical investigation of this latex. However, as a vibrational spectroscopic technique Raman spectroscopy has several advantageous properties for this type of research. The aim of this study is to investigate whether Raman spectroscopy can be used as an alternative analytical technique to monitor the chemical reactions in Lactarius latex. Therefore, this paper presents the first Raman spectra of Lactarius latex and provides an interpretation of the Raman bands that are present. L. lacunarum latex spectra are thoroughly investigated by 2D correlation analysis and are compared with latex spectra of other species (L. chrysorrheus, L. deterrimus, L. fluens, L. glyciosmus and L. salmonicolor).