Analytical potential of mid-infrared detection in capillary electrophoresis and liquid chromatography: a review

Literature published in the last decade concerning the use of mid-infrared spectrometry as a detection system in separation techniques employing a liquid mobile phase is reviewed. In addition to the continued use of isocratic liquid chromatographic (LC) techniques, advances in chemometric data evaluation techniques now allow the use of gradient techniques on a routine basis, thus significantly broadening the range of possible applications of LC-IR. The general trend towards miniaturized separation systems was also followed for mid-IR detection where two key developments are of special importance. Firstly, concerning on-line detection the advent of micro-fabricated flow-cells with inner volumes of only a few nL for transmission as well as attenuated total reflection measurements enabled on-line mid-IR detection in capillary LC and opened the path for the first successful realization of on-line mid-IR detection in capillary zone electrophoresis as well as micellar electrokinetic chromatography. Secondly, concerning off-line detection the use of micro-flow through dispensers now enables to concentrate eluting analytes on dried spots sized a few tens of micrometers, thus matching the dimensions for sensitive detection by mid-IR microscopy. Finally in an attempt to increase detection sensitivity of on-line mid-IR detection, mid-IR quantum cascade lasers have been used. Applications cover the field of food analysis, environmental analysis and the characterization of explosives among others. Best detection sensitivities for on-line and off-line detection have been achieved in miniaturized systems and are in the order of 50 ng and 2 ng on column, respectively.     

Chemiluminescence aptasensor for cocaine based on double-functionalized gold nanoprobes and functionalized magnetic microbeads

This year inductively coupled plasma mass spectrometry (ICP-MS) moves into the fourth decade of development. In this article, some recent trends and developments in ICP-MS are reviewed, with special focus on instrumental development and emerging applications. Some key trends include a novel mass spectrometer for elemental and speciation analysis in Mattauch–Herzog geometry with a focal-plane-camera array detector. The reason for this development is the possibility to record the full elemental mass range simultaneously and all the time. Monitoring fast transient signals in chromatography or laser ablation is now possible and will become an important asset in future studies, e.g., for isotope ratio analysis. In addition, there is a lot of new activity and interest in the area of nanosciences and medicine. Here, instrumental developments are reported that allow the direct analysis of microparticles and single cells.     

Comparative study of mobile Raman instrumentation for art analysis

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.     

Application of isotope dilution ICP–MS techniques to quantitative proteomics

ICP–MS techniques based on isotope dilution analysis can be regarded as an emerging tool in quantitative protein analysis. Well-known concepts, for example species-specific and unspecific isotope dilution analysis, which promoted accurate and precise quantification in elemental speciation studies, have nowadays been transferred to the analysis of large biomolecules, e.g. proteins. Besides detection of heteroatom-containing proteins, the artificial introduction of metal-containing labels has attracted much attention and, as a consequence, ICP–MS-based isotope dilution techniques can serve as a valuable quantification tool. In particular, because isotope dilution ICP–MS techniques can enable absolute protein quantification, they can be regarded as an attractive technique in current and prospective proteomics. In this review, recent developments and applications will be highlighted and critically assessed.     

Analysis of fresco by laser induced breakdown spectroscopy

The laser-based techniques have been shown to be a very powerful tool for artworks characterization and are used in the field of cultural heritage for the offered advantages of minimum invasiveness, in situ applicability and high sensitivity. Laser induced breakdown spectroscopy, in particular, has been applied in this field to many different kinds of ancient materials with successful results. In this work, a fragment of a Roman wall painting from the archaeological area of Pompeii has been investigated by LIBS. The sample elemental composition resulting from LIBS measurements suggested the presence of certain pigments. The ratio of the intensities of different lines related to some characteristic elements is proposed as an indicator for pigment recognition.     

Detecting art forgeries using LA-ICP-MS incorporating the in situ application of laser-based collection technology

The nature of art lends itself to forgery as a skilled and determined forger can mimic the techniques and styles of an artist to a level where even an expert can be duped. The authentication of paintings is a subjective process, but modern techniques may provide the means to provenance artist pigments based on elemental composition. This study applies laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to the analysis of artist paints from different manufacturers to identify variation between the elemental association patterns of these materials. The technique facilitates comparison of the paints used by an artist with produced works of art to assist provenancing initiatives of questioned materials. The effects of the trace element profiles of the backing substrate and binder on analytical data were also identified. By applying the technique to paint scraped from real paintings, a limited database was created to allow comparison to be made with some of Australian artist, Kathleen O’Connor's artworks and assist in determining production chronology. Data from this study were able to facilitate comparison of blue paints from two different paintings and confirm their co-provenance consequently determining the relative production date of a separate painting of previously unknown age.Preliminary trials of a prototype collection device designed to reduce damage and allow for in situ sampling of artworks were also undertaken. The device, which allows direct laser-based sampling of a complete painting, was tested using a Francis Ryan painting. The prototype allows for the collection of debris directly generated by LA-ICP-MS of a predefined area of a painting prior to subsequent analysis using direct LA-ICP-MS. This collection method significantly minimizes the amount of damage produced by conventional sampling methods. Analyses of the debris collected, using the prototype, were found to be comparable to the scrapings of equivalent paint analysed using direct LA-ICP-MS analysis.     

Behaviour of phospholipids in analytical reactive pyrolysis

Checking for the presence of egg in a painting layer allows to decide whether or not it is a tempera. Several already assessed analytical techniques may be used to perform the chemical analysis for the detection of egg in paintings. As an advantageous and alternative methodology for the determination of egg, a new application of analytical pyrolysis, hyphenated with gas chromatography–mass spectrometry (GC–MS) system, in presence of hexamethyldisilazane (HMDS) and tetramethylammonium-hydroxide (TMAH), is reported here. The innovation lays mainly in the choice of new markers for the presence of egg. It is here demonstrated that in art diagnostic tris-TMS-ester and methyl ester of phosphoric acid, generated by the pyrolysis of standard phospholipids and synthetic painting layers containing egg as binding medium, may be used as new markers for identification of egg in tempera layers. The adoption of these new markers in analytical pyrolysis allows to obtain higher analytical performance with respect to classical markers (fatty acids), especially in terms of yield and, as a consequence, in terms of limit of detection.     

Structure,Spectral Properties,and Complexing Ability of 1-Phenyl-3-methylpyrazol-5-one Ferrocenoyl Hydrazone

A potentially tridentate coordinating chelating ligand system, 1-phenyl-3-methylpyrazol-5-one ferrocenoylhydrazone, has been synthesized. Structure of the obtained ligand and its equilibrium forms in the solution has been elucidated from the data of elemental analysis, IR, electronic absorption and NMR (1H, 13C, and 15N NMR including 1H–1H COSY, 1H–1H NOESY, 1H–13C HSQC, 1H–13C HMBC, and 1H–15N HMBC 2D correlation techniques) spectroscopy as well as quantum chemistry methods. The reactions of 1-phenyl-3-methylpyrazol-5-one ferrocenoylhydrazone with selected transition metal ions have afforded metal chelates, their composition, the mode of coordination, and type of tautomeric form of the coordinated ligand being dependent on the metal nature.     

Application of emission spectrometer with laser sampler to microanalysis of pigments from Hubert Robert’s canvas painting

Laser-induced breakdown spectroscopy has been applied to layer-by-layer pigment material microanalysis from the different sections of Hubert Robert’s (1733–1808) painting “Landscape of a Pool with an Obelisk and Ruins of an Aqueduct”. This painting consists of two sections and, therefore, requires thorough examination of the pigments from both sections in order to identify their authenticity. The data obtained on the elemental composition of the paint layers including the ground layer alongside with art examination have formed the basis for the identification, attribution and restoration of both investigated sections of the painting.     

X-ray mapping in electron-beam instruments.

This review traces the development of X-ray mapping from its beginning 50 years ago through current analysis procedures that can reveal otherwise obscure elemental distributions and associations. X-ray mapping or compositional imaging of elemental distributions is one of the major capabilities of electron beam microanalysis because it frees the operator from the necessity of making decisions about which image features contain elements of interest. Elements in unexpected locations, or in unexpected association with other elements, may be found easily without operator bias as to where to locate the electron probe for data collection. X-ray mapping in the SEM or EPMA may be applied to bulk specimens at a spatial resolution of about 1 microm. X-ray mapping of thin specimens in the TEM or STEM may be accomplished at a spatial resolution ranging from 2 to 100 nm, depending on specimen thickness and the microscope. Although mapping has traditionally been considered a qualitative technique, recent developments demonstrate the quantitative capabilities of X-ray mapping techniques. Moreover, the long-desired ability to collect and store an entire spectrum at every pixel is now a reality, and methods for mining these data are rapidly being developed.     

Multilayers quantitative X-ray fluorescence analysis applied to easel paintings

X-ray fluorescence spectrometry (XRF) allows a rapid and simple determination of the elemental composition of a material. As a non-destructive tool, it has been extensively used for analysis in art and archaeology since the early 1970s. Whereas it is commonly used for qualitative analysis, recent efforts have been made to develop quantitative treatment even with portable systems. However, the interpretation of the results obtained with this technique can turn out to be problematic in the case of layered structures such as easel paintings. The use of differential X-ray attenuation enables modelling of the various layers: indeed, the absorption of X-rays through different layers will result in modification of intensity ratio between the different characteristic lines. This work focuses on the possibility to use XRF with the fundamental parameters method to reconstruct the composition and thickness of the layers. This method was tested on several multilayers standards and gives a maximum error of 15% for thicknesses and errors of 10% for concentrations. On a painting test sample that was rather inhomogeneous, the XRF analysis provides an average value. This method was applied in situ to estimate the thickness of the layers a painting from Marco d’Oggiono, pupil of Leonardo da Vinci.     

Surface analysis in the semiconductor industry: Present use and future possibilities

Secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) represent three surface analysis techniques heavily used in the complementary metal oxide semiconductor (CMOS) industry. The maturity of these techniques is demonstrated by (a) the diversity of lab-based instruments used in research and development (R&D) as well as to support fab-related issues and (b) the fact that highly automated platforms have now been or are being introduced into the fab for process control. Some recent developments of interest in the lab R&D space include the following: (a) the introduction of Orbitrap mass spectrometers into SIMS, (b) the introduction of higher energy monochromated photon sources into standalone lab-based XPS, and (c) the introduction of commercialized vacuum–scanning probe microscopy (SPM) platforms. The possibilities this opens are demonstrated through (a) SIMS analysis of organics from photoresist materials, (b) XPS subsurface analysis, ie, beyond the sputter front during depth profiling, and (c) SPM analysis of 2D material properties sensitive to the ambient environment, to mention a few.     

Fingerprinting of egg and oil binders in painted artworks by matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis of lipid oxidation by-products

A matrix-assisted laser desorption ionization time-of-flight mass spectrometry-based approach was applied for the detection of various lipid classes, such as triacylglycerols (TAGs) and phospholipids (PLs), and their oxidation by-products in extracts of small (50–100 μg) samples obtained from painted artworks. Ageing of test specimens under various conditions, including the presence of different pigments, was preliminarily investigated. During ageing, the TAGs and PLs content decreased, whereas the amount of diglycerides, short-chain oxidative products arising from TAGs and PLs, and oxidized TAGs and PLs components increased. The examination of a series of model paint samples gave a clear indication that specific ions produced by oxidative cleavage of PLs and/or TAGs may be used as markers for egg and drying oil-based binders. Their elemental composition and hypothetical structure are also tentatively proposed. Moreover, the simultaneous presence of egg and oil binders can be easily and unambiguously ascertained through the simultaneous occurrence of the relevant specific markers. The potential of the proposed approach was demonstrated for the first time by the analysis of real samples from a polyptych of Bartolomeo Vivarini (fifteenth century) and a “French school” canvas painting (seventeenth century).     

Solution properties and solvatochromism of bis(<Emphasis Type="Italic">N</Emphasis>-2-pyridyl-salicylaldiminato)cobalt(II)

The bis(N-2-pyridyl-salicylaldiminato)cobalt(II) complex ([Co(sap)₂]), a reddish-pink crystalline compound has been characterized by elemental analysis, molar conductivity, cyclic voltammetry, and Vis–NIR spectroscopy. Combination of all techniques indicates a tetrahedral geometry for the complex in solid state and in the solvents used. Electronic spectroscopy was used to determine the ligand–field parameters as well as chromaticity coordinates; for discrimination of color changes CIE and CIELAB color spaces have been applied.     

Detection of heavy metals in Arabian crude oil residue using laser induced breakdown spectroscopy

Laser induced breakdown spectroscopy (LIBS) was applied for the elemental analysis of Arabian crude oil residue samples. The spectra due to trace elements such as Ca, Fe, Mg, Cu, Zn, Na, Ni, K and Mo were recorded using this technique. The dependence of time delay and laser beam energy on the elemental spectra was also investigated. Prior to quantitative analysis, the LIBS system was calibrated using standard samples containing these trace elements. The results achieved through this method were compared with conventional technique like inductively coupled plasma.     

Phase transformation in spodumene–diopside glass

In situ developments of platelike spodumene–diopside grains were obtained by controlled devitrification of the complex system Li₂O–CaO–MgO–Al₂O₃–SiO₂ glass. The crystallization mechanisms of spodumene–diopside glass were measured by isothermal and non-isothermal processes using classical and differential thermal analysis techniques. The Avrami constant n was 2.0–2.1, indicating two-dimensional crystal growth and platelike grains. The crystalline phases precipitated first were high-quartz_s.s., then transformed to β-spodumene and diopside. The Flexural strength, fracture toughness and thermal shock resistance (in 20°C water) increased from 145 MPa, 1.3 MPa m^1/2, 800°C (pure spodumene) to 197 MPa, 2.9 MPa m^1/2 and 920°C (spodumene–diopside) with low thermal expansion coefficient (from 3∼9·10^–7 to 11.8·10^–7 K^–1). This mean in situ developments of platelike spodumene–diopside grains reinforced the low thermal expansion coefficient glass-ceramics.     

Portable Raman monitoring of modern cleaning and consolidation operations of artworks on mineral supports

Any restoration performed on cultural heritage artworks must guarantee a low impact on the treated surfaces. Although completely risk-free methods do not exist, the use of tailor-made procedures and the continuous monitoring by portable instrumentation is surely one of the best approaches to conduct a modern restoration process. In this work, a portable Raman monitoring, combined sometimes with spectroscopic techniques providing the elemental composition, is the key analysis technique in the three-step restoration protocol proposed: (a) in situ analysis of the surface to be treated (original composition and degradation products/pollutants) and the cleaning agents used as extractants, (b) the thermodynamic study of the species involved in the treatment in order to design a suitable restoration method and (c) application and monitoring of the treatment. Two cleaning operations based on new technologies were studied and applied to two artworks on mineral supports: a wall painting affected by nitrate impact, and a black crusted stone (chalk) altarpiece. Raman bands of nitrate and gypsum, respectively, decreased after the step-by-step operations in each case, which helped restorers to decide when the treatment was concluded, thus avoiding any further damage to the treated surface of the artworks.     

Development of a multiplexed chemiluminescent immunochemical imaging technique for the simultaneous localization of different proteins in painting micro cross-sections

The identification and localization of organic components in the complex stratigraphy of paintings play a crucial role in studies of painting techniques and authentication, restoration, and conservation of artworks. Much scientific effort has been expended for the development of analytical approaches suitable for the investigation and characterization of organic substances, allowing high sensitivity, specificity, and spatial resolution. Proteins (e.g., ovalbumin, casein, and collagen from different animal sources) are one of the classes of organic substances most widely used as painting materials. The analytical techniques commonly used for their analysis (micro Fourier transform infrared spectroscopy, chromatographic techniques, and proteomic approaches) have limits related to the lack of specificity or to the absence of information concerning the stratigraphic localization of the detected proteins. Immunological techniques are a promising alternative approach for the characterization of proteins in artworks. Thanks to the high specificity of antigen–antibody reactions, these techniques are widely used for the analysis of proteins in bioanalytical and clinical chemistry and recently they have been successfully applied in the field of science for conservation of cultural heritage. The present research aimed to develop an ultrasensitive chemiluminescent immunochemical procedure for the simultaneous localization of ovalbumin and bovine casein (two common proteins found in binding media or varnishes of artistic and archaeological samples) in resin-embedded painting micro cross-sections. The possibility of performing the simultaneous identification of different proteins in painting cross-sections is of particular relevance in the field of cultural heritage because samples are often small and available in a limited number; therefore, the maximum amount of information must be obtained from each of them.     

Structural studies of water and other hydrogen—bonded liquids by neutron diffraction

The structural characteristics of hydrogen-bonded liquids may be studied by neutron diffraction. A brief review of the experimental techniques is given with particular emphasis on H/D isotope substitution and temperature difference techniques. These methods are illustrated with reference to recent work on water in its normal and supercooled liquid phases. The temperature variation is linked to the behaviour of the hydrogen bonds and the evolution towards the continuous random network of amorphous ice. A brief report is made for some other hydrogen-bonded liquids, contrasting the strong correlations in hydrogen fluoride which are not well understood with the study of methanol which gives good agreement with computer simulation results. Formic acid has also been investigated and novel techniques used in the analysis of the H/D datasets. The review ends with an overview of current issues and a consideration of future developments.     

Separation and Determination of Monovalent and Divalent Cations by the Facile Propylsulfonic Acid Functionalized Silica Stationary Phase

A facile strong cation-exchange stationary phase based on propylsulfonic acid functionalized silica was prepared through the oxidation in situ of 3-mercaptopropyl silica and characterized by elemental analysis and X-ray photoelectron spectroscopy. The phase was used to separate monovalent and divalent inorganic cations with strong acid as mobile phase. Simultaneous separation of alkali metals and alkaline earth metals was examined and the cations sodium, magnesium and calcium in tap water were determined.