The gas-phase on-line production of vanadium oxytrihalides, VOX3 and their identification by infrared spectroscopy

A new route has been devised, leading to the production of VOX3 molecules where X=F, Br and I by an on-line process using vanadium oxytrichloride, VOCl3 as a starting compound passed over the following heated salts NaF, KBr and KI at 375, 700 and 550 degrees C, respectively. The products have been characterized by the IR spectra of their vapors. The low resolution gas phase on-line Fourier transform infrared spectra reported for the first time show strong bands with PQR type structure, centered at 1058, 1035, 1030 and 1025 cm(-1) assigned to the v1(a1), the O=V stretching fundamental mode of VOF3, VOCl3 VOBr3 and VOI3, respectively.     

The gas-phase on-line production of vanadium oxytrihalides, VOX3 and their identification by infrared spectroscopy

A new route has been devised, leading to the production of VOX₃ molecules where X=F, Br and I by an on-line process using vanadium oxytrichloride, VOCl₃ as a starting compound passed over the following heated salts NaF, KBr and KI at 375, 700 and 550°C, respectively. The products have been characterized by the IR spectra of their vapors. The low resolution gas phase on-line Fourier transform infrared spectra reported for the first time show strong bands with PQR type structure, centered at 1058, 1035, 1030 and 1025 cm⁻¹ assigned to the ν₁(a₁), the O=V stretching fundamental mode of VOF₃, VOCl₃, VOBr₃ and VOI₃, respectively.     

The gas-phase on-line formation of antimony oxide trihalides, SbOX3 where X = F and Cl and their identifications by infrared spectroscopy

Antimony oxide trihalides, SbOX3 molecules, where X = F or Cl have been produced, by means of an on-line process, using antimony trichloride, SbOCl3 as starting material passed over heated silver oxide at 230 degrees C. The antimony oxide trichloride SbOCl3 formed is then reacted with sodium fluoride, NaF at 550 degrees C to produce antimony oxide trifluoride, SbOF3. The products have been characterized by the IR spectra of their vapors. Low resolution gas-phase Fourier transform infrared spectra show strong bands centered at 1272 and 1217 cm(-1), assigned to nu1(a1), the O=Sb stretching fundamental of SbOF3 and SbOCl3, respectively. Both observed bands show typical PQR-type structure with a strong Q-head.     

Process control of apple winemaking by low-resolution gas-phase Fourier-transform infrared spectroscopy

Four apple wine fermentation processes have been observed by means of direct-inlet gas-phase FTIR spectroscopy. The apple juice concentrates were each fermented by two species of Saccharomyces cerevisiae starters, and the experiment was repeated. The development of the concentrations of 1-propanol, 4-methylpyridine, acetaldehyde, acetic acid, and ethyl acetate was monitored. Two different sampling methods were used--static headspace and direct injection of the must. The performance of the FTIR method is limited by the high ethanol concentration. It can be mathematically proven that the amount of sample can be selected so that any distortion due to ethanol is minimized. Headspace GC-MS was used for preliminary compound identification.     

Stability of gas-phase tartaric acid anions investigated by quantum chemistry, mass spectrometry, and infrared spectroscopy

In an effort to understand the chemical factors that stabilize dianions, experimental and theoretical studies on the stability of the tartrate dianion were performed. Quantum chemical calculations at the coupled cluster level reveal only a metastable state with a possible decomposition pathway (O(2)C-CH(OH)-CH(OH)-CO(2))(2-) → (O(2)C-CH(OH)-CH(OH))(?-) + CO(2) + e(-) explaining the observed gas-phase instability of this dianion. Further theoretical data were collected for the bare dianion, this molecule complexed to water, sodium, and a proton, in both the meso and l forms as well as for the uncomplexed radical anion and neutral diradical. The calculations suggest that the l-tartrate dianion is more thermodynamically stable than the dianion of the meso stereoisomer and that either dianion can be further stabilized by association with a separate species that can help to balance the charge of the molecular complex. Mass spectrometry was then used to measure the energy needed to initiate collisionally induced dissociation of the racemic tartrate dianion and for the proton and sodium adducts of both the racemic and meso form of this molecule. Infrared action spectra of the dianion stereoisomers complexed with sodium were also acquired to determine the influence of the metal ion on the vibrations of the dianions and validate the computationally predicted structures. These experimental data support the theoretical conclusions and highlight the instability of the bare tartrate dianion. From the experimental work, it could also be concluded that the pathway leading to dissociation is under kinetic control because the sodium adduct of the racemic stereoisomer dissociated at lower collisional energy, although it was calculated to be more stable, and that decomposition proceeded via C-C bond dissociation as computationally predicted. Taken together, these data provide insight into the gas-phase stability of the tartrate dianion and highlight the role of adducts in stabilizing this species.     

The site of Cr+ attachment to gas-phase aniline from infrared spectroscopy

Infrared spectroscopy of gas-phase Cr+ complexes of aniline was studied using the FELIX free electron laser interfaced to a Fourier transform ion cyclotron resonance spectrometer. For both the monomer complex Cr+(aniline) and the dimer complex Cr+(aniline)2 the spectra showed features indicating binding of the metal ion to the aromatic pi cloud, as opposed to the nitrogen atom. Agreement with DFT-calculated infrared absorption spectra for the ring-bound complexes was good using the MPW1PW91 functional, but the B3LYP functional predicted the wrong binding site. The spectroscopic results resolve the ambiguity in computational prediction of the preferred binding site and support the use of the MPW1PW91 functional for these systems.     

Discrimination of industrial products by on-line near infrared spectroscopy with an improved dendrogram

Near infrared(NIR) spectroscopy technique has shown great power and gained wide acceptance for analyzing complicated samples.The present work is to distinguish different brands of tobacco products by using on-line NIR spectroscopy and pattern recognition techniques.Moreover,since each brand contains a large number of samples,an improved dendrogram was proposed to show the classification of different brands.The results suggest that NIR spectroscopy combined with principal component analysis (PCA) and hierarchical cluster analysis(HCA) performs well in discrimination of the different brands,and the improved dendrogram could provide more information about the difference of the brands.     

Analysis and identification of different animal horns by a three-stage infrared spectroscopy

In this study, a new method, a three-stage infrared spectroscopy (Fourier transform infrared spectroscopy (FT-IR) integrated with second derivative infrared spectroscopy and two-dimensional correlation infrared spectroscopy (2D-IR)) was developed to analyze the organic and inorganic compositions of three different horns (Cornu Antelopis, Cornu Bubali and Pulvis Cornus Bubali Concentratus). In IR spectra, all the three horns had their own macroscopic fingerprints especially for those compositions containing amide groups, CH groups and Ca(3)(PO(4))(2). Their second derivative spectra amplified the differences and revealed the potentially characteristic IR absorption bands 1350-400 cm(-1) to be investigated in 2D-IR. Subsequently, many covered characteristic fingerprints were disclosed in 2D-IR spectra in the range of 1350-400 cm(-1) and the three horns were therefore effectively discriminated. Meanwhile, the analysis results of inorganic constituents were verified by atomic spectroscopy. Furthermore, thirty different horn samples including ten of each horn were also successfully classified by soft independent modeling of class analogy (SIMCA). It was demonstrated that the above three-stage infrared spectroscopy could be applicable for quick, non-destructive and effective analysis and identification of very complicated and similar mixture systems (e.g. traditional Chinese medicines).     

The determination of vanadium,molybdenum and tungsten by infrared spectroscopy

The infrared spectra of the 8-hydroxyquinolinates of molybdenum, vanadium and tungsten in the region 3–15 μ were investigated. It was found possible to determine the elements quantitatively, singly or in pairs, with an error of about 3%. Molybdenum was determined at 10.80 μ and 10.93 μ, vanadium at 10.50 μ, and tungsten at 10.61 μ or 10.90 μ.     

Polychlorobiphenyls differentiation and identification by gas chromatography/fourier transform infrared spectroscopy

Reference infrared vapour phase spectra of 20 polychlorobiphenyls (PCBs) have been obtained by gas chromatography/Fourier transform infrared spectroscopy (GC/FTIR). These spectra are consistent with those of PCB obtained by diffuse reflectance IR spectroscopy (DRIFT) and with those of more simple molecular structures (iodochlorobenzenes, 1-bromodichlorobenzenes). The IR frequencies of the GC/FTIR spectra of PCB are assigned in terms of substitution patterns. This work shows that GC/FTIR can be a good approach for differentiation and identification of PCB in complex mixtures.     

The determination of periodate by infrared spectroscopy

An infrared method has been developed to determine periodate on the microgram scale. Periodate is precipitated in slightly acid solution with tetraphenylarsonium chloride and in presence of perchlorate as carrier. The precipitate is mixed with powdered potassium bromide and pressed into a disc. The base-line absorbance of the periodate band at 11.68 μ is calculated in order to find the concentration of periodate from a calibration curve. No interference is caused by perchlorate, permanganate, perrhenate, chlorate, iodate or bromate.     

The determination of nitrate by infrared spectroscopy

Summary Nitrate may be determined by precipitation with nitron acetate and determination of the absorbance at 7.3 in a potassium bromide disc. The results are reproducible at milligram levels with a standard deviation of around ±5%. The presence of twice the amount of nitrite, perchlorate, bromate, chlorate, chromate, periodate or iodide has no significant effect on the determination.

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Zusammenfassung Nach Fällung mit Nitronacetat läßt sich Nitrat durch Messung der Absorption bei 7,3 in Kaliumbromid bestimmen. Die Resultate sind im Milligramm-Maßstab mit einer Standardabweichung von etwa ±5% reproduzierbar. Die gleichzeitige Anwesenheit der doppelten Menge Nitrit, Perchlorat, Bromat, Chlorat, Chromat, Perjodat oder Jodid hat keinen merklichen Einfluß auf die Bestimmung.

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Résumé On peut doser les nitrates par précipitation par l'acétate de nitron et mesure de l'absorption à 7,3 sur pastille en bromure de potassium. Les résultats sont reproductibles à l'échelle du milligramme avec une déviation standard de ±5% environ. La présence d'une quantité double de nitrites, perchlorates, bromates, chlorates, chromates, periodates ou iodures ne produit pas d'effet important sur le dosage.

     

Analysis and identification of irradiated Spirulina powder by a three-step infrared macro-fingerprint spectroscopy

A three-step infrared (IR) macro-fingerprint method combining conventional IR spectra, and the secondary derivative spectra with two-dimensional infrared correlation spectroscopy (2D-IR), was developed to analyze Spirulina powder before and after gamma irradiation. In the IR spectra, most of the absorption peaks of samples irradiated at 1, 2.7, 6, and 10.4 kGy had lower intensities than the non-irradiated ones, whereas peaks at 1152, 1078, and 1051 cm⁻¹ were slightly enhanced with irradiation at 2.7, 6, and 10.4 kGy. Their second derivative spectra amplified the differences and revealed that irradiation affected the C=O band of carboxylic acid and esters, and the N–H band of proteins. The peaks at 1746 and 1741 cm⁻¹, and those at 1730 and 1725  cm⁻¹ became two broad peaks. Meanwhile, the three sharp peaks at 1548 cm⁻¹, 1544 cm⁻¹ and 1536 cm⁻¹ changed to two broad peaks at around 1547 and 1534 cm⁻¹ after irradiation at doses higher than 1 kGy. The characteristic IR bands from 1700 cm⁻¹ to 1600 cm⁻¹, which represent the C=O band in proteins, also have different shapes and intensities after irradiation. The finding indicated that irradiation affected the secondary structures of protein which was confirmed by curve fitting results. During the process of increasing the temperature from 50 to 210 °C, the ratio of amide I to II in absorption intensities in the 2D-IR spectra of the irradiated samples varied with different response for different samples. Saccharides in Spirulina powder had a higher thermostability than proteins, but the autopeaks of irradiated samples did show differences from the non-irradiated sample. The intensity of autopeaks at 1012 cm⁻¹ increased dramatically in the irradiated samples while that of peaks at 1053, 1071, and 1083 cm⁻¹ decreased after irradiation. Based on the three-step IR macro-fingerprint method, irradiated Spirulina powder samples were successfully and fast identified and discriminated.     

Structural characterization by infrared multiple photon dissociation spectroscopy of protonated gas-phase ions obtained by electrospray ionization of cysteine and dopamine

Structural characterization of protonated gas-phase ions of cysteine and dopamine by infrared multiple photon dissociation (IRMPD) spectroscopy using a free electron laser in combination with theory based on DFT calculations reveals the presence of two types of protonated dimer ions in the electrospray mass spectra of the metabolites. In addition to the proton-bound dimer of each species, the covalently bound dimer of cysteine (bound by a disulfide linkage) has been identified. The dimer ion of m/z 241 observed in the electrospray mass spectra of cysteine has been identified as protonated cystine by comparison of the experimental IRMPD spectrum to the IR absorption spectra predicted by theory and the IRMPD spectrum of a standard. Formation of the protonated covalently bound disulfide-linked dimer ions (i.e. protonated cystine) from electrospray of cysteine solution is consistent with the redox properties of cysteine. Both the IRMPD spectra and theory indicate that in protonated cystine the covalent disulfide bond is retained and the proton is involved in intramolecular hydrogen bonding between the amine groups of the two cysteine amino acid units. For cysteine, the protonated covalently bound dimer (m/z 241) dominated the mass spectrum relative to the proton-bound dimer (m/z 243), but this was not the case for dopamine, where the protonated monomer and the proton-bound dimer were both observed as major ions. An extended conformation of the ethylammonium side chain of gas-phase protonated dopamine monomer was verified from the correlation between the predicted IR absorption spectra and the experimental IRMPD spectrum. Dopamine has the same extended ethylamine side chain conformation in the proton-bound dopamine dimer identified in the mass spectra of electrosprayed dopamine. The structure of the proton-bound dimer of dopamine is confirmed by calculations and the presence of an IR band due to the shared proton. The presence of the shared proton in the protonated cystine ion can be inferred from the IRMPD spectrum.

Comparing near infrared and Raman spectroscopy for on-line monitoring of emulsion copolymerization reactions

In this work, Raman and Near InfraRed (NIR) spectroscopies are evaluated for the monitoring of different semicontinuous emulsion homo- and co-polymerization reactions. Important process variables, namely monomer concentrations and average particle sizes, were monitored by both techniques under realistic conditions that would be found in an industrial environment (e.g. low signal/noise ratio, probe placed in the reaction medium). Results suggest that Raman and NIR are suitable for on-line monitoring of emulsion polymerization reactions and that the success of their application is mainly related to representative calibration models used for the estimation of the properties of interest.     

Vibrational spectroscopy of gas-phase neutral and cationic phenanthrene in their electronic groundstates

Various experimental methods are applied to retrieve the vibrational structure of phenanthrene in its neutral and cationic groundstates. The linear infrared (IR) absorption spectra in the 400-1650 cm(-1) range of jet-cooled phenanthrene and its cation, both clustered with either an argon or a neon atom, are obtained via photo-induced cluster dissociation spectroscopy. The spectra observed are in good agreement with calculated spectra of the bare species. However, the observed spectrum of cationic phenanthrene shows more lines and lines with different intensities in the 900-1400 cm(-1) range than expected from calculations. Additional spectra of the perdeuterated phenanthrene Ar cation, and the warm (T approximately > room temperature) bare phenanthrene cation are recorded. Also the mass-analyzed threshold ionization spectra of bare phenanthrene and phenanthrene-Ar are recorded and compared with each other. Comparison of the spectral data recorded to calculated spectra of bare neutral, cationic and cationic perdeuterated phenanthrene, as well as to IR spectra recorded in matrix-isolation experiments, explicitly demonstrates that cluster dissociation spectroscopy is a valid and powerful method to obtain IR spectroscopic information of bare neutral and cationic jet-cooled poly-aromatic hydrocarbons.     

Improved accuracy of on-line heavy water measurement using infrared spectroscopy by investigation of signal-to-noise ratio and temperature influences

Experimental protocols for the on-line measurement of heavy water concentration in nuclear power plants have been established, and important parameters, such as the temperature and signal-to-noise ratio, which govern the accuracy of measurement, have been studied. The temperature of a sample should be controlled tightly because the temperature variation introduces non-linear baseline variations and leads to an increase of the partial least squares calibration error. Furthermore, the variation in the signal-to-noise ratio of spectra sensitively influences the calibration. For reliable prediction, it is critical to maintain the signal-to-noise ratio at a certain level. When the sample spectra were collected at a higher temperature, it was possible to acquire spectra with an improved signal-to-noise ratio and better calibration. In addition, a single beam spectrum of water shifts to a lower frequency, and the maximum transmission intensity at around 2500 cm(-1)(the heavy water band location) increases at an elevated temperature. Overall, an on-line infrared spectroscopic scheme is presented for measuring heavy water. The scheme can be applied to an actual process without practical difficulties. If the spectra could be collected at elevated temperature over 2 min with the use of a high throughput light source, the prediction error could reach to 1.0 ppm.     

The identification of fibers by infrared and Raman microspectroscopy

The application of Raman and infrared microspectroscopy to fiber identification has been investigated. Natural and synthetic fibers, both organic and inorganic in nature, can be rapidly characterized by these techniques. In general, it has been found that infrared microspectroscopy offers a nonsubjective method of fiber identification that is quicker, easier, and occasionally, more selective than classical methods. Raman microspectroscopy has also been proven useful for these analyses. It provides low-frequency information, requires virtually no sample preparation, and supplies data complementary to that furnished by infrared microspectroscopy. In many cases one may use these methods for a quick differentiation of fibers of the same type which have undergone different chemical treatments.     

Size-exclusion chromatography with on-line ultraviolet, proton nuclear magnetic resonance and mass spectrometric detection and on-line collection for off-line Fourier transform infrared spectroscopy.

The coupling of HPLC with UV detection and on-line NMR spectroscopy and mass spectrometry combined with a dedicated interface for the collection of the chromatographic eluent for subsequent Fourier transform (FT) IR has been investigated using a number of polymer additives as model compounds. Size-exclusion chromatography was performed using deuterated chloroform as eluent with the separation monitored on-line by UV detection at 254 nm and on-flow 1H-NMR and MS. The effluent from the NMR probe was directed to a dedicated HPLC interface where it was deposited on a germanium plate for subsequent FT-IR. NMR and MS spectra were successfully obtained for 2,6-di-tert.-butyl-4-methylphenol, octadecyl-3-(3,5-di-tert.-butyl-4-hydroxyphenyl) propionate (Irganox 1076) and diisooctyl phthalate on-line and FT-IR spectra for all three compounds were obtained off-line. Practical problems encountered with this multiple hyphenation are described.     

Analysis of azanaphthalenes and their enzyme oxidation products by high-performance liquid chromatography, infrared spectroscopy and mass spectrometry

Adsorption and reversed-phase high-performance liquid chromatography (HPLC) have been successfully used to separate metabolites from the parent heterocycles (isoquinoline, 3-methylisoquinoline, phthalazine, quinazoline, quinoxaline and cinnoline). Retention data are reported. The metabolites, hydroxyazanaphthalenes, which arise as a result of aldehyde oxidase catalysed oxidation, could be extracted in microgram quantities from incubation mixtures by n-butanol. Complete identification of the oxidation products was achieved by collecting fractions corresponding to each compound from the HPLC eluate and subjecting these to infrared and mass-spectral analysis.