X–ray Single Crystal Structure and Raman Spectrum of Ammonium Hexafluoroarsenate

The structure of ammonium hexafluoroarsenate, NH₄AsF₆, has been determined by X‐ray diffraction using a single crystal grown from saturated solution in anhydrous HF. NH₄AsF₆ crystallizes rhombohedral with the KOsF₆ structure type, with a = 7.459(3) Å, c = 7.543(3) Å (at 200 K), Z = 3, space group (No. 148). No phase transition was observed in the 100 K–296 K temperature range. The structure is dominated by regular AsF₆ octahedra and disordered NH₄⁺ cations. Raman spectrum of a single crystal of NH₄AsF₆ shows the bands at 372 cm^?1, 572 cm^?1, 687 cm^?1 (AsF₆^?) and at 3240 cm^?1 and 3360 cm^?1 (NH₄⁺).     

Combined use of liquid chromatography-nuclear magnetic resonance spectroscopy and liquid chromatography-mass spectrometry for the characterization of an acarbose degradation product

Directly coupled LC-MS and LC-NMR were applied to identify and structurally characterize an acarbose degradation product A in acidic media. A comparative analysis of the stop-flow LC-NMR (1H and TOCSY) and LC-MS data provided evidence that A is structurally related to acarbose, differing from the parent compound in a number of subunits present in the molecule. Spectral analysis revealed that A was the alpha-glucosidase inhibitor amylostatin XG. Complementary information obtained from the two methods led to the structural elucidation of A which was later corroborated by high-resolution NMR spectroscopy of the isolated molecule.     

Interlaboratory study comparing analyses of simulated angle‐resolved X‐ray photoelectron spectroscopy data

An interlaboratory study has been conducted to determine the following: (i) the similarities and differences of film thicknesses and composition profiles obtained from analyses of simulated angle‐resolved X‐ray photoelectron spectroscopy (ARXPS) data by different analysts using different algorithms for data analysis, and (ii) the effects of two assumptions commonly made in data‐analysis algorithms for ARXPS on derived film thicknesses and composition profiles. The analyzed data were generated by the National Institute of Standards and Technology Database for the Simulation of Electron Spectra for Surface Analysis, (SESSA) which provides a simple way to study the influence of the aforementioned effects on compositional depth profile reconstruction. Sets of simulated ARXPS data were produced for thin films of SiO₂, SiON, HfO₂, and HfON of varying thicknesses on a Si substrate. For some HfON films, the N concentration varied with depth. Eleven groups participated in the round robin study. The majority (eight) employed a commercial ARXPS instrument in which the angular distribution is measured for a fixed sample geometry, in contrast to conventional ARXPS in which the sample is tilted for angular variation. The average deviations between the reported average depth, film thickness, and amount of material typically varied between 20% and 30% but were considerably larger, between 30% and 80%, for some cases. The average errors were generally larger for simulations that included elastic scattering and the finite analyzer‐acceptance angle (realistic conditions) than those for simulations that neglected elastic scattering and the finite analyzer‐acceptance angle (simplified conditions). The retrieved N depth profiles were quantitatively different from the true depth profiles and showed substantial variability among the group of members who used the same instrument and analysis software. Copyright © 2014 John Wiley & Sons, Ltd.     

Uncertainty quantification in theoretical spectroscopy: The structural sensitivity of X‐ray emission spectra

We present a methodology for analyzing the dependence of molecular spectra calculated with quantum‐chemical methods on the underlying molecular structure. This analysis is applied to investigate the structural sensitivity of calculated valence‐to‐core X‐ray emission (VtC‐XES) spectra for the test case of three iron carbonyl complexes, Fe(CO)₅, [FeCp(CO)₂(THF)]⁺ (Cp = cyclopentadienyl, THF = tetrahydrofuran), and Fe(CO)₃(cod) (cod = cyclooctadienyl). Based on this analysis, we discuss how the VtC‐XES spectra depend on changes of metal–ligand bond distances and bond angles as well as on the structure of the ligands. The benefits of such an analysis of the structural sensitivity are discussed. Our methodology can serve as a first step toward quantifying and accounting for uncertainties due to the underlying model structure in theoretical spectroscopy.     

Separation and characterization of alkyl phenol formaldehyde resins demulsifier by adsorption chromatography, gel permeation chromatography, infrared spectrometry and nuclear magnetic resonance spectroscopy

This paper deals with the separation and characterization of alkyl phenol formaldehyde resins demulsifier by infrared spectrometry and nuclear magnetic resonance spectroscopy after separation of the different surfactants and low molecular additives by adsorption chromatography. Firstly, the types of surfactants are identified by methylene blue chloride-chloroform test method and the elemental analysis such as Ca, K, Mg, Na, P, S and N. Then, the different surfactants and low molecular components are separated by adsorption chromatography after parts of low molecular components are dried in an oven, and the molecular weight distribution is measured by gel permeation chromatography also. Finally, the separated surfactants are determined by Fourier transform infrared (FTIR) spectrometry and nuclear magnetic resonance (NMR) spectroscopy. The distortionless enhancement by polarization transfer (DEPT), H, C correlated spectroscopy (H, C-COSY), H, H correlated spectroscopy (H, H-COSY) and heteronuclear multiple-bond correlation (HMBC) spectroscopy are applied to determine the molecular structures.     

Characterizing polymorphism and crystal transformation of polylactide by terahertz time-domain spectroscopy

Terahertz time-domain spectroscopy (THz-TDS), which has been proved to show promising application in complex polymer systems, was employed to investigate the polymorphism phenomenon and crystal transformation of polylactide (PLA) in this study. The THz-TDS shows sensitive response on the crystal structure. The α'-form, α-form and stereocomplex crystals exhibit absorption peaks of lattice vibration at 1.82, 2.01 and 2.09 THz, respectively. THz-TDS has no direct chirality identification on the difference between poly (d-lactide) (PDLA) and poly(l-lactide) (PLLA). However, the PLA stereocomplex shows an extra and distinctive absorption peak at 1.43 THz compared with homo-PLA, and the peak was proved to be stemmed from the collective vibration of L-lactic unit and D-lactic unit pairs connecting by hydrogen bonds. This is the first time that THz-TDS has been proved to be of great potential in identification of polymer stereocomplex crystal. Also, the α'→α crystal transformation of PLA were intuitively investigated at 120 °C using THz-TDS, while the transformation rate was quite slow.     

Analysis of glycans in glycoproteins by diffusion-ordered nuclear magnetic resonance spectroscopy

Enzymatically cleaved glycans from sub-milligram quantities of erythropoietin (EPO) and ovalbumin have been analyzed, without further purification, by two-dimensional diffusion-ordered nuclear magnetic resonance spectroscopy. At NMR sample concentrations below 50 μmol L⁻¹ the major components of the oligosaccharide fractions could be distinguished by their anomeric proton chemical shift and their size-dependent diffusion coefficients. Figure ¹H NMR diffusion decay curves of anomeric protons in the EPO glycan fraction     

Synthesis, X-ray diffraction analysis and NMR studies of (Z)-2-methyl-3-triphenylstannyl-3-pentene-2-ol

The synthesis of (Z)-2-methyl-3-triphenylstannyl-3-pentene-2-ol and its characterization by an X-ray diffraction study and multinuclear NMR are reported. The tin atom exhibits a distorted tetrahedral SnC₄ geometry with the four Sn---C bond distances experimentally equivalent. The slight distortion from the ideal tetrahedral geometry is because of the presence of a weak intramolecular HO → Sn interaction of 3.012(3) Å which produces a loose four-membered ring. The title compound was characterized in solution by ¹H, ¹³C and ¹¹⁹Sn NMR, and the persistence of the weak intramolecular HO → Sn coordination in solution was revealed by ¹³C and ¹¹⁹Sn secondary isotope multiplet of partially labelled entities (SIMPLE-NMR) experiments.     

Routine FT-Raman spectroscopy with modified standard FT-IR instrument

A commercial FT-IR spectrometer (BRUKER IFS 66) was combined with a Raman module, having an NdYAG laser as source, a sample compartment, a filter for elimination of the exciting line from the spectrum and a detector. The interferometer and computer of the IFS 66 was used to record Raman spectra of small amounts of liquids and solids using a spherical sapphire sample cell.     

Stabilisation of ultra-high molecular weight polyethylene with Vitamin E

Ultra-high molecular weight polyethylene (UHMWPE) has been the material of choice for load-bearing articular components used in total joint arthroplasty in the past 30 years. However, the durability of the whole implant has often been compromised by oxidation of UHMWPE components. Since the use of a suitable, biocompatible stabilizer would minimize this inconvenience, the possibility of adding synthetic Vitamin E to medical grade UHMWPE is currently under investigation.In the present work, medical grade UHMWPE was blended with 0.05, 0.1 or 0.5 w/w% of α-tocopherol and consolidated by compression moulding. Small blocks of reference UHMWPE and of each blend were then gamma irradiated to 30 or 100 kGy. FTIR spectroscopy was used to monitor changes in both the polymer and the additive. Thin sections of virgin and α-tocopherol doped UHMWPE irradiated and unirradiated were aged in a ventilated oven at 90 °C and the kinetic of oxidation was followed by FTIR. In addition, CL-imaging curves were recorded at 180 °C on both irradiated and unirradiated samples.Phenol loss is observed in all the α-tocopherol doped samples upon irradiation. Hypotheses on the rearrangements of the additive structure include the formation of quinonoid products. Nevertheless, all the additive-containing samples exhibit better oxidation resistance compared to the virgin material, indicating stabilizing activity of the α-tocopherol derivatives.     

Analysis of the electronic structure of Hf(Si0.5As0.5)As by X-ray photoelectron and photoemission spectroscopy

The ternary hafnium silicon arsenide, Hf(Si_xAs_1−x)As, has been synthesized with a phase width of 0.5?x?0.7. Single-crystal X-ray diffraction studies on Hf(Si_0.5As_0.5)As showed that it adopts the ZrSiS-type structure (Pearson symbol tP6, space group P4/nmm, Z=2, a=3.6410(5) Å, c=8.155(1) Å). Physical property measurements indicated that it is metallic and Pauli paramagnetic. The electronic structure of Hf(Si_0.5As_0.5)As was investigated by examining plate-shaped crystals with laboratory-based X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoemission spectroscopy (PES). The Si 2p and As 3d XPS binding energies were consistent with assignments of anionic Si¹⁻ and As^1-. However, the Hf charge could not be determined by analysis of the Hf 4f binding energy because of electron delocalization in the 5d band. To examine these charge assignments further, the valence band spectrum obtained by XPS and PES was interpreted with the aid of TB-LMTO band structure calculations. By collecting the PES spectra at different excitation energies to vary the photoionization cross-sections, the contributions from different elements to the valence band spectrum could be isolated. Fitting the XPS valence band spectrum to these elemental components resulted in charges that confirm that the formulation of the product is Hf²⁺[(Si_0.5As_0.5)As]²⁻.     

Characterisation of a synthesised fluorescent ligand (4-acridinol-1-sulphonic acid) using nuclear magnetic resonance spectroscopy

The synthesis and complete characterisation of the fluorescent ligand, 4-acridinol-1-sulphonic acid (the acridine analogue of 8-quinolinol-5-sulfonic acid) is described. Using a judicious array of nuclear magnetic resonance spectroscopy experiments, the structural elucidation and full assignment of all proton and carbon chemical shifts were afforded. The 4-acridinol-1-sulphonic acid was found to behave in a similar manner to 8-quinolinol-5-sulphonic acid, forming fluorescent complexes with magnesium(II) and zinc(II). The uncorrected emission maxima for the metal-acridinol complexes were found to be at around 620 nm compared to 505 nm for the respective quinolinol complexes. Unfortunately, preliminary spectrofluorimetric analytical figures of merit revealed that the detection limits of the new acridinol metal complexes were one and a half orders of magnitude poorer than those attained with the corresponding quinolinol ligand. However, in contrast to 8-quinolinol-5-sulphonic acid, the 4-acridinol-1-sulphonic acid ligand showed considerable selectivity for magnesium(II) and zinc(II) over aluminium(III).     

Li2Si3O7: Crystal structure and Raman spectroscopy

The crystal structure of metastable Li₂Si₃O₇ was determined from single crystal X-ray diffraction data. The orthorhombic crystals were found to adopt space group Pmca with unit cell parameters of , and . The content of the cell is Z=4. The obtained structural model was refined to a R-value of 0.035. The structure exhibits silicate sheets, which can be classified as [Si₆O₁₄] using the silicate nomenclature of Liebau. The layers are build up from zweier single chains running parallel to c. Raman spectra are presented and compared with other silicates. Furthermore, the structure is discussed versus Na₂Si₃O₇.     

On the synthesis and structure of monoaryllead and diaryllead acetates RPb(OCOCH3)3 and R2Pb(OCOCH3)2

Anhydrous monoaryllead triacetates ArPb(OAc)₃ (Ar = Ph, p-Tolyl, o-Tolyl, 2,5-Xylyl; OAc = OCOMe) were prepared by arylation of Pb(OAc)₄ with ArSn(C₄H₉-n)₃ in the presence of Hg(OCOCF₃)₂. The procedure was adapted for the synthesis of diaryllead diacetates Ar₂Pb(OAc)₂ (Ar = Ph, p-Tolyl, o-Tolyl, p-ClC₆H₄, o-ClC₆H₄) and afforded products with higher purity than other procedures. The crystal structures of PhPb(OAc)₃, Ph₂Pb(OAc)₂ and (o-Tolyl)₂Pb(OAc)₂ were determined by X-ray diffraction. PhPb(OAc)₃ and (o-Tolyl)₂Pb(OAc)₂ are monomeric. The pentagonal bipyramid around Pb in PhPb(OAc)₃, like the trapezoidal bipyramid around Pb in (o-Tolyl)₂Pb(OAc)₂, is heavily distorted, the OAc groups being unsymmetrically chelating. Lead in Ph₂Pb(OAc)₂ is in a distorted octahedral environment. One OAc group is bridging, linking the molecular units to infinite chains, the other OAc group is symmetrically chelating. IR, ¹H, ¹³C and ²⁰⁷Pb NMR spectroscopic data are reported. The structures of p-TolPb(OAc)₃, o-TolPb(OAc)₃ and 2,5-XylPb(OAc)₃ are inferred to be similar to that of PhPb(OAc)₃, and the structure of (o-ClC₆H₄)₂Pb(OAc)₂ is inferred to be similar to that of (o-Tolyl)₂Pb(OAc)₂.     

Direct on-line hyphenation of capillary liquid chromatography to nuclear magnetic resonance spectroscopy: practical aspects and application to drug metabolite identification

In combining the high peak concentrations of capillary liquid chromatography (CapLC) with the high mass sensitivity of micro scale nuclear magnetic resonance (NMR) the hyphenation of CapLC to micro NMR offers a substantial gain in overall sensitivity. This paper deals with our experiences gained using a commercial CapLC-NMR system which has very recently become available. The limits of detection (SNR > 3) for a test compound of a molecular weight of M 318 were found to be approximately 100 ng (0.35 nmol) within an hour acquisition time and approximately 25 ng over night (85 pmol). Practical aspects such as the feasibility of stopped-flow experiments and sample handling issues are discussed in detail and first possible drug metabolite applications to hepatocyte incubations and direct analysis of plasma samples are presented.     

Zirconium titanate ceramic pigments: Crystal structure, optical spectroscopy and technological properties

Srilankite-type zirconium titanate, a promising structure for ceramic pigments, was synthesized at 1400 °C following three main doping strategies: (a) ZrTi_1−xA_xO₄, (b) ZrTi_1−x−yA_xB_yO₄ and (c) Zr_1−xC_xTiO₄ where A=Co, Cr, Fe, Mn, Ni or V (chromophores), B=Sb or W (counterions) and C=Pr (chromophore); x=y=0.05. Powders were characterized by XRD with Rietveld refinements and DRS in the UV-visible-NIR range; technological properties were appraised in several ceramic matrices (frits, glazes and body). Zirconium titanate can be usefully coloured with first row transition elements, giving green and greenish yellow (Co and Ni); orange-buff (Cr and V); tan-brown hues (Mn and Fe). In industrial-like synthesis conditions, a disordered structure as (Zr,Ti)O₂, with both Zr and Ti randomly distributed in the octahedral site, is achieved. Doping with chromophores and counterions induces unit cell dimensions variation and causes an oversaturation in zirconium oxide. Optical spectroscopy reveals the occurrence of Co²⁺, Cr³⁺, Fe³⁺, Mn²⁺, Mn³⁺, Ni²⁺, V³⁺ and V⁴⁺. The zirconium titanate pigments fulfil current technological requirements for low-temperature applications, but exhibit a limited chemico-physical stability for higher firing temperature and in chemically aggressive media.     

Surface structure of cationic surfactant solutions investigated by angular resolved X‐ray photoelectron spectroscopy with calibrated transmission function

The main goal of the present work is to investigate the surface structure of cationic surfactant solutions by angular resolved X‐ray photoelectron spectroscopy (ARXPS) after calibrating transmission function of the spectrometer. We have estimated the transmission function of the ARXPS spectrometer, and with it, we investigated solution of tetrabutylammonium iodide in a nonaqueous polar solvent. By genetic algorithm, the fractional concentration‐depth profiles of constituents were reconstructed. These depth profiles evidence the enrichment of surfactant and the depletion of solvent in the surface regime and verify the separate distributions of oppositely charged surfactant ions. From those profiles we draw a conclusion that there is a preferred orientation for cation present at the surface, and the possibility for cation to take this orientation is related to its surface amount. Copyright © 2010 John Wiley & Sons, Ltd.     

Characterization of sodium laureth sulfate by reversed-phase liquid chromatography with evaporative light scattering detection and H nuclear magnetic resonance spectroscopy

A direct and effective method utilizing reversed-phase liquid chromatography combined with evaporative light scattering detection was developed to determine the relative ratio of different alkyl chain lengths, to quantify the average ethylene oxide (EO) level and to identify EO distribution in the presence of sodium laureth sulfates. A C8 bonded silica gel column and an acetonitrile–water gradient mobile phase containing ammonium acetate were used as the best stationary and mobile phase, respectively. The results were confirmed by nuclear magnetic resonance spectroscopy. The detection limit was 80 μg/mL and the calibration curve, i.e., the log–log plots (peak area vs. concentration), was linear in the working range of 80–4200 μg/mL with R² values of above 0.999 (in the case of 3 mol sodium laureth sulfates). Furthermore, the application of the chromatographic method to a commercial product without pretreatment was presented. The raw material was identified by fast atom bombardment mass spectrometry.