Hydrogen bonding in selected vanadates: a Raman and infrared spectroscopy study

Water plays an important role in the stability of minerals containing the deca and hexavanadates ions. A selection of minerals including pascoite, huemulite, barnesite, hewettite, metahewettite, hummerite has been analysed. Infrared spectroscopy combined with Raman spectroscopy has enabled the spectra of the water HOH stretching bands to be determined. The use of the Libowitsky type function allows for the estimation of hydrogen bond distances to be determined. The strength of the hydrogen bonds can be assessed by these hydrogen bond distances. An arbitrary value of 2.74A was used to separate the hydrogen bonds into two categories such that bond distances less than this value are considered as strong hydrogen bonds whereas hydrogen bond distances greater than this value are considered relatively weaker. Importantly infrared spectroscopy enables the estimation of hydrogen bond distances using an empirical function.     

Micro methods in infrared and Raman spectroscopy

Summary Employing the concept of the optical conductance [1–3] and taking into account the spectroscopic properties of the sample, firstly the features of sample arrangements are given, which are using minimal amounts of sample determined by the condition of complete illumination of the different types of spectrometers and using different techniques for infrared, near-infrared and Raman micro spectroscopy. Secondly, arrangements of a micro sample are discussed, the minimal size of which is determined by the laws of diffraction. In this case the spectrometers are usually not fully illuminated. The minimal amount of sample necessary is for infrared microscopy in the order of 1000 m³ (1 pg), for Raman microscopy of the order 100 m³ (0.1 pg). Examples demonstrate the state of the art and finally developments, which can be anticipated, are outlined.     

Applications of infrared and Raman spectroscopy in industry

Summary There have been many recent explosive advances in both IR and Raman spectroscopy which have developed in response to industrial problems of increasing complexity. Probably the biggest factor in these advances has been computerization, which has contributed not only to substantial improvements in data handling but to enormous gains in sensitivities of analyses as well.In this paper numerous examples of Raman and IR applications in industry are given using many of these recent advances, including in-situ techniques, microprobe analyses, unusual combinations of instruments — i.e., hyphenated methods — and new sample handling techniques. The bright future of FT-IR and Raman spectroscopy is also briefly discussed.

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Anwendungen der Infrarot- und Ramanspektroskopie in der Industrie

Zusammenfassung Infrarot- und in geringerem Maße Raman-Spektroskopie sind etablierte und wirklich alltägliche Techniken in einem gut ausgerüsteten Industrielabor. Sie werden routinemäßig bei Problemen eingesetzt, die von großer Bedeutung für den Erfolg einer Forschungs- und Entwicklungsindustrie sind.Die Untersuchung von Katalysatorstrukturen und der Oberflächenadsorptionsstellen in Hinblick auf Katalysevorgänge kann Isotopensubstitution und in situ Bestimmungen bei mittleren bis hohen Drücken und Temperaturen einschließen. Für die in situ Untersuchungen von Katalysatoren ist Raman-Spektroskopie die einfachere Methode, da das Trägermaterial keinen Einfluß hat.Untersuchungen bei hohen Drücken sind wichtig für Modellstudien bei der Ölproduktionsforschung, da hier Bandenpositionen und -intensitäten von gasförmigen/flüssigen Mischungen von Kohlenwasserstoffen mit dem Druck korreliert und für die Analyse der Zusammensetzung verwendet werden.Relativ neue Entwicklungen in der Schwingungsspektroskopie, wie Mikrotechniken und Mikroskopanordnungen, berühren alle Gebiete der Forschung und Entwicklung, die für die Ölindustrie typisch sind. Dazu gehören in der Raman-Spektroskopie die räumliche Trennung von Probe und Detektionssystem, die durch optische Fibern überbrückt wird, und viele Probentechniken in der IR-Spektroskopie wie IRAS, DRIFT und FTIR-PAS. In situ IRAS ist eine sehr leistungsstarke Methode bei der Untersuchung von beschichteten Metalloberflächen, Adhäsionsschichten und des zeitlichen Verhaltens von Beschichtungen bei Wärmebehandlung.Bei vielen analytischen Problemen liegen komplexe Gemische vor, zu deren Lösung Verbundverfahren wie GC/ FT-IR oder TGA/FT-IR beitragen können. Ebenso ist ein mobiles FT-IR-Spektrometer ein interessantes und sehr nützliches Konzept. Schließlich werden Beispiele für spektroskopische Einzelanalysen gezeigt, die entweder die besonderen oder auch die sich ergänzenden Möglichkeiten der FT-IR- und Raman-Spektroskopie ausnutzen.

     

Raman spectroscopy of selected arsenates--implications for soil remediation

The contamination of soils with heavy metals such as As, Cr and Cu is of great importance; the remediation of such soils even more so. Arsenic compounds are prevalent in soils either through leaching of mine tailings, the use of Cu/Cr/As as a wood preservative or through the use of arsenic in cattle dips. The arsenic compounds in soils and leachates can be highly reactive and mobile, resulting in the formation of metal arsenate compounds. Of these compounds, one such set of minerals that can be formed is the vivianite arsenate minerals. Raman spectroscopy has been used to characterise the vivianite arsenates and to identify arsenic contaminants in a soil.     

Internal modes by Raman and infrared spectroscopy of benzylidenemalononitrile

The polarized Raman spectra of a single crystal of benzylidenemalononitrile (BMN), as well as the infrared spectrum of a powder sample, have been measured.An assignment of the 48 fundamental vibrations is proposed, based on group frequency correlations, Raman and i.r. intensities and comparison with the spectra of parent molecules.     

Raman spectroscopy of selected lead minerals of environmental significance

The Raman spectra of the minerals cerrusite (PbCO(3)), hydrocerrusite (Pb(2)(OH)(2)CO(3)), phosgenite (Pb(2)CO(3)Cl(2)) and laurionite (Pb(OH)Cl) have been used to qualitatively determine their presence. Laurionite and hydrocerrusite have characteristic hydroxyl stretching bands at 3506 and 3576 cm(-1). Laurionite is also characterised by broad low intensity bands centred at 730 and 595 cm(-1) attributed to hydroxyl deformation vibrations. The minerals cerrusite, hydrocerrusite and phosgenite have characteristic CO (nu(1)) symmetric stretching bands observed at 1061, 1054 and 1053 cm(-1). Phosgenite displays complexity in the CO (nu(3)) antisymmetric stretching region with bands observed at 1384, 1327 and 1304 cm(-1). Cerrusite shows bands at 1477, 1424, 1376 and 1360 cm(-1). The hydrocerrusite Raman spectrum has bands at slightly different positions from cerrusite, with bands at 1479, 1420, 1378 and 1365 cm(-1). The complexity of the nu(3) region is also reflected in the nu(2) and nu(4) regions with the observation of multiple bands. Laurionite is characterised by two intense bands at 328 and 272 cm(-1) attributed to PbO and PbCl stretching bands. Importantly, all four minerals are characterized by their Raman spectra, enabling the mineral identification in leachates and contaminants of environmental significance.     

Raman and infrared spectroscopy of the manganese arsenate mineral allactite

The mineral allactite [Mn(7)(AsO(4))(2)(OH)(8)] is a basic manganese arsenate which is highly pleochroic. The use of the 633 nm excitation line enables quality spectra of to be obtained irrespective of the crystal orientation. The mineral is characterised by a set of sharp bands in the 770-885 cm(-1) region. Intense and sharp Raman bands are observed at 883, 858, 834, 827, 808 and 779 cm(-1). Collecting the spectral data at 77K enabled better band separation with narrower bandwidths. The observation of multiple AsO(4) stretching bands indicates the non-equivalence of the arsenate anions in the allactite structure. In comparison the infrared spectrum shows a broad spectral profile with a series of difficult to define overlapping bands. The low wavenumber region sets of bands which are assigned to the nu(2) modes (361 and 359 cm(-1)), the nu(4) modes (471, 452 and 422 cm(-1)), AsO stretching vibrations at 331 and 324 cm(-1), and bands at 289 and 271 cm(-1) which may be ascribed to MnO stretching modes. The observation of multiple bands shows the loss of symmetry of the AsO(4) units and the non-equivalence of these units in the allactite structure. The study shows that highly pleochroic minerals can be studied by Raman spectroscopy.     

Pressure-tuning infrared and Raman spectroscopy of group 14 tetraphenyl compounds

The effect of high external pressures on the vibrational spectra of the tetraphenyl Group 14 compounds, Ph4M (M = Si, Ge, Sn, Pb), were examined between ambient pressure and 40 kbar with the aid of a diamond-anvil cell. The four compounds displayed similar behaviour as the pressure was increased and a structural transition at approximately 15 kbar, most probably associated with a phenyl ring rotation, was identified in each case. The pressure dependencies of selected vibrational modes were obtained.     

Near infrared fourier transform Raman spectroscopy of human artery

We report the first near IR FT-Raman spectroscopy of normal diseased human artery. In normal human aorta, two bands at 1669 cm⁻¹ and 1452 cm⁻¹ dominate the spectrum and can be assigned to protein amide I and C-H in-plane bending vibrations, respectively. Weaker bands are also observed between 1250 and 1350 cm⁻¹. Non-calcified atherosclerotic lesions with a large amount of necrotic debris below the tissue surface show a relative increase in the intensity of the 1452 cm⁻¹ band. In atherosclerotic aortas which contain calcified deposits several hundred microns below the tissue surface, a strong 961 cm⁻¹ band is observed due to the symmetric stretch of phosphate groups in the calcified salts. The results show that this method provides the capability to probe biological substituents several hundred microns below the tissue surface.     

Future advances in near infrared Fourier Transform Raman spectroscopy

The probable directions in which the technique of near infrared Fourier Transform Raman spectroscopy will advance are discussed. The analysis considers the limitations of the method and the instrumental balances which may be found for different applications. Discussion is from an instrumental viewpoint, including filtering, detection, excitation, sampling techniques and data analysis. Applications of these advances in the analytical environment are suggested. Spectra are presented from a system which employs Q-switched Nd:YAG excitation and a gated detector in order to discriminate against long-lived spectral backgrounds. Dramatic reductions in the background from hot samples are demonstrated.     

Raman spectroscopy of selected copper minerals of significance in corrosion

The Raman spectroscopy of selected minerals of the corrosion products has been measured including nantokite, eriochalcite, claringbullite, atacamite, paratacamite, clinoatacamite and brochantite and related minerals. The free energy of formation shows that each mineral is stable relative to copper metal. The mineral, which is formed in copper corrosion, depends on the kinetics and conditions of the reaction. Raman spectroscopy clearly identifies each mineral by its characteristic Raman spectrum. The Raman spectrum is related to the mineral structure and bands are assigned to CuCl stretching and bending modes and to SO stretching modes. Clinoatacamite is identified as the polymorph of atacamite and not paratacamite. Paratacamite is a separate mineral with a similar but different structure to that of atacamite.     

Fourier-transform infrared and Raman difference spectroscopy studies of the phosphorus-containing dendrimers

FT IR and Raman spectra of 12 generations of the phosphorus-containing starburst dendrimers containing P=S and P=O bonds with terminal aldehyde and P-Cl groups were compared. The influence of the encirclement on the band frequencies and intensity is studied and due to the predictable, controlled and reproducible structure of the dendrimers the information usually inaccessible is obtained. Bands in the IR difference (G2'(P=O)-G2'(P=S)) spectra have characteristic EPR-like form. The strong band at 1600 cm(-1) show marked changes of the optical density in dependence of the aldehyde (-CH=O) or azomethyne (-CH=N-) substituents in the aromatic ring. The analysis of difference spectra enables one to assign the characteristic bands nu(P=S) and nu(P=O) for the bonds in the core, in the repeating unit and in the terminal groups of the dendrimers. This assignment is supported by the calculation of the absorption curves of the different fragments of dendrimer with the force constants and electro-optical parameters. The IR and Raman spectra of dendrimers are depended on the ratio of number terminal groups to a number of repeating units, which in its turn is strictly determined by the generation number. Thus, the marked differences in the vibrational spectra of the first successive generations aspire to zero for the higher ones. The rather rigid repeated units with little conformational flexibility define the perfect microstructure of the studied phosphorus-containing dendrimers up to the eleventh generation.     

Differentiation of selected blue writing inks by surface-enhanced Raman spectroscopy

Raman spectroscopy and surface enhanced Raman spectroscopy were used to examine 14 blue inks obtained from commercially available stationery. Standard colouring agents in the inks: β-phase of phtalocyanine blue PB15 and some homologues of the methyl violet class, were identified. Surface enhanced Raman spectra were recorded on a firm heterostructure of silver/nanocrystalline diamond/silicon constituting an active substrate providing the possibility to write directly on the surface. Based on the differences in traditional and surface enhanced Raman spectra, two inks were identified unambiguously, the remaining inks were categorised into three groups exhibiting common spectral features. Despite their similarity, surface enhanced Raman spectra exhibited soft variations enabling discrimination of the inks, thus proving the usefulness of the method.     

Fourier Transform Raman and infrared spectroscopy of N-phenylmaleimide and methylene dianiline bismaleimide

We have carried out a comprehensive assignment of the infrared and Raman spectra of N-phenylmaleimide, including N-(perdeuterophenyl)maleimide. As part of this work, we have measured the depolarization ratios of N-phenylmaleimide in solution. To our knowledge this is the first time that polarization data have been recorded using FT Raman spectroscopy from a solution rather than a pure liquid. The assignments for N-phenylmaleimide have been used to assign the bands of a commercial bismaleimide, methylene dianiline bismaleimide (MDA-BMI), that change on curing. This has allowed a better understanding of the chemistry involved.     

Comparative analysis of smokeless gunpowders by Fourier transform infrared and Raman spectroscopy

Fourier Transform Infrared (FTIR) and Raman spectroscopic techniques were used to perform a comparative study of the spectral profiles of single-base, double-base and triple-base smokeless gunpowders. Preliminary results based on visual comparison of the spectra point out that spectra obtained by both vibrational techniques were useful for a rapid identification of gunpowders containing dinitrotoluene as one of the major components and triple-base gunpowders. Additionally, the Raman spectra of gunpowders with diphenylamine in its primary composition showed a characteristic band, assigned to 2-nitro-diphenylamine, allowing the identification of this type of gunpowders.     

Monitoring cellular responses upon fatty acid exposure by Fourier transform infrared spectroscopy and Raman spectroscopy

We investigated the applicability of FTIR-spectroscopy as a high throughput screening method for detection of biochemical changes in intact liver cells in bulk upon fatty acid exposure. HepG2 cells adapted to serum free (HepG2-SF) growth were exposed to four different fatty acids, three octadecenoic acids, differing in cis/trans-configuration or double bond position (oleic acid, elaidic acid and vaccenic acid) as well as palmitic acid in three days. High throughput FTIR spectroscopic measurements on dried films of intact cells showed spectra with high signal-to-noise ratio and great reproducibility. When applying principal component analysis (PCA) a clear discrimination between fatty acid exposures was observed. Higher levels of triacylglycerides were accumulated in cells exposed to elaidic acid than when exposed to the other fatty acids; the least accumulation appeared to be in cells exposed to palmitic acid. An increased absorption at ~966 cm(-1) corresponding to trans-double bond was detected upon elaidic acid exposure but not upon vaccenic acid exposure. Instead, upon vaccenic acid exposure two new absorption bands were observed at 981 and 946 cm(-1) due to the presence of double bond conjugation. Raman spectroscopy on single cells, with and without treatment by vaccenic acid, confirmed the presence of conjugation. By fatty acid composition analysis, the conjugation was further specified to be conjugated linoleic acid (CLA) isomers. Thus, instead of being preserved as a monounsaturated fatty acid, vaccenic acid was converted into CLA in HepG2 cells. The results demonstrate the applicability of high-throughput FTIR spectroscopy as an explorative method in in vitro systems from which biologically relevant hypotheses can be generated and further investigated.     

Raman and infrared spectroscopy of arsenates of the roselite and fairfieldite mineral subgroups

Raman spectroscopy complimented with infrared spectroscopy has been used to determine the molecular structure of the roselite arsenate minerals of the roselite and fairfieldite subgroups of formula Ca(2)B(AsO(4))(2).2H(2)O (where B may be Co, Fe(2+), Mg, Mn, Ni and Zn). The Raman arsenate (AsO(4))(2-) stretching region shows strong differences between the roselite arsenate minerals which is attributed to the cation substitution for calcium in the structure. In the infrared spectra complexity exists with multiple (AsO(4))(2-) antisymmetric stretching vibrations observed, indicating a reduction of the tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong Raman bands around 450 cm(-1) are assigned to nu(4) bending modes. Multiple bands in the 300-350 cm(-1) region assigned to nu(2) bending modes provide evidence of symmetry reduction of the arsenate anion. Three broad bands for roselite are found at 3450, 3208 and 3042 cm(-1) and are assigned to OH stretching bands. By using a Libowitzky empirical equation hydrogen bond distances of 2.75 and 2.67 A are estimated. Vibrational spectra enable the molecular structure of the roselite minerals to be determined and whilst similarities exist in the spectral patterns, sufficient differences exist to be able to determine the identification of the minerals.     

Metabolic fingerprinting in disease diagnosis: biomedical applications of infrared and Raman spectroscopy

The ability to diagnose the early onset of disease, rapidly, non-invasively and unequivocally has multiple benefits. These include the early intervention of therapeutic strategies leading to a reduction in morbidity and mortality, and the releasing of economic resources within overburdened health care systems. Some of the routine clinical tests currently in use are known to be unsuitable or unreliable. In addition, these often rely on single disease markers which are inappropriate when multiple factors are involved. Many diseases are a result of metabolic disorders, therefore it is logical to measure metabolism directly. One of the strategies employed by the emergent science of metabolomics is metabolic fingerprinting; which involves rapid, high-throughput global analysis to discriminate between samples of different biological status or origin. This review focuses on a selective number of recent studies where metabolic fingerprinting has been forwarded as a potential tool for disease diagnosis using infrared and Raman spectroscopies.