Determination of sulfinpyrazone and two of its metabolites in human plasma and urine by gas chromatography and selective detection

A selective and sensitive gas chromatographic method for simultaneous determination of sulfinpyrazone and two of its metabolites (the para-hydroxylated metabolite and the sulfone metabolite) in biological fluids using alkali flame ionization detection (AFID), electron capture detection (ECD) and mass fragmentographic detection is described. The compounds are extracted from the samples, methylated and separated on 2% OV-17 or 3% OV-225 columns. Phenylbutazone is used as internal standard. Standard curves are linear. The coefficient of variation at 10 microgram/ml of sulfinpyrazone in plasma was shown to be 1.8% (AFID), and the detection limits were 0.1 microgram/ml (AFID) and 10 ng/ml (ECD). Mass spectra of the methylated compounds are shown and serum concentration curves after oral administration of 100 mg sulfinpyrazone to two persons are determined together with the excreted amounts of drug and metabolites.     

Refinement of borate structures from 11B MAS NMR spectroscopy and density functional theory calculations of 11B electric field gradients

The refinement of borate structures using DFT calculations combined with experimental (11)B quadrupole coupling parameters from solid-state NMR spectroscopy is presented. The (11)B electric field gradient (EFG) tensors, calculated using the WIEN2k software for trigonal and tetrahedral boron sites in a series of model compounds, exhibit a convincing linear correlation with the quadrupole coupling tensor elements, determined from (11)B MAS NMR spectra of the central or satellite transitions. The model compounds include Li(2)B(4)O(7), Mg(2)B(2)O(5), Mg(3)B(2)O(6), NH(4)B(C(6)H(5))(4), and colemanite (CaB(3)O(4)(OH)(3).H(2)O). The (11)B quadrupole moment, Q = 0.0409 +/- 0.0002 barn, derived from the linear correlation, is in excellent agreement with the accepted value for Q((11)B). This demonstrates that DFT (WIEN2k) calculations can provide precise (11)B quadrupole coupling parameters on an absolute scale. On the other hand, DFT calculations based on the reported crystal structures for datolite (CaBSiO(4)(OH)) and danburite (CaB(2)Si(2)O(8)) cannot reproduce the experimental (11)B quadrupole coupling parameters to the same high precision. However, optimization of these structures by minimization of the forces between the atoms (obtained by DFT) results in a significant improvement between the calculated and experimental (11)B quadrupole coupling parameters, which indicates that reliable refinements of the borate structures are obtained by this method. Finally, the DFT calculations also provide important structural information about the sign and orientation of the EFG tensor elements in the crystal frame, a kind of information that cannot be achieved from (11)B NMR experiments on powdered samples.     

On the determination of crystallinity and cellulose content in plant fibres

A comparative study of cellulose crystallinity based on the sample crystallinity and the cellulose content in plant fibres was performed for samples of different origin. Strong acid hydrolysis was found superior to agricultural fibre analysis and comprehensive plant fibre analysis for a consistent determination of the cellulose content. Crystallinity determinations were based on X-ray powder diffraction methods using side-loaded samples in reflection (Bragg-Brentano) mode. Rietveld refinements based on the recently published crystal structure of cellulose Iβ followed by integration of the crystalline and amorphous (background) parts were performed. This was shown to be straightforward to use and in many ways advantageous to traditional crystallinity determinations using the Segal or the Ruland–Vonk methods. The determined cellulose crystallinities were 90–100 g/100 g cellulose in plant-based fibres and 60–70 g/100 g cellulose in wood based fibres. These findings are significant in relation to strong fibre composites and bio-ethanol production.     

Procedure for background estimation in energy-dispersive X-ray fluorescence spectra

A method for semi-automatic background estimation in energy-dispersive x-ray fluorescence spectra is outlined. Two cubic splines were investigated and the spline called the Butland interpolant was chosen for further investigation. Prior to the calculation of the spline, peak regions are set up, and suitable knots are defined outside the peak regions. To set up the peak regions, an automatic peak-search routine and a calibration equation are used. For a given peak, the latter relates the full width at half maximum (FWHM) to the peak centre. In turn, the size of the peak regions are defined by the FWHM multiplied by a constant given by the user. The method was tested on several types of spectra. It was found that the optimal size of the peak region decreased with increasing peak density. Reproducibility tests showed that the standard deviation of the summation of counts within a peak region and after background subtraction was less than would be expected from the counting statistics.     

High-Resolution Infrared Synchrotron Investigation of (HCN)2 and a Semi-Experimental Determination of the Dissociation Energy D0

The high-resolution infrared absorption spectrum of the donor bending fundamental band ν of the homodimer (HCN)₂ has been collected by long-path static gas-phase Fourier transform spectroscopy at 207 K employing the highly brilliant 2.75 GeV electron storage ring source at Synchrotron SOLEIL. The rovibrational structure of the ν transition has the typical appearance of a perpendicular type band associated with a Σ–Π transition for a linear polyatomic molecule. The total number of 100 assigned transitions are fitted employing a standard semi-rigid linear molecule Hamiltonian, providing the band origin ν₀ of 779.05182(50) cm⁻¹ together with spectroscopic parameters for the degenerate excited state. This band origin, blue-shifted by 67.15 cm⁻¹ relative to the HCN monomer, provides the final significant contribution to the change of intra-molecular vibrational zero-point energy upon HCN dimerization. The combination with the vibrational zero-point energy contribution determined recently for the class of large-amplitude inter-molecular fundamental transitions then enables a complete determination of the total change of vibrational zero-point energy of 3.35±0.30 kJ mol⁻¹. The new spectroscopic findings together with previously reported benchmark CCSDT(Q)/CBS electronic energies [Hoobler et al. ChemPhysChem. 19 , 3257–3265 (2018)] provide the best semi-experimental estimate of 16.48±0.30 kJ mol⁻¹ for the dissociation energy D₀ of this prototypical homodimer.     

Stress-Induced Domain Wall Motion in a Ferroelastic Mn3+ Spin Crossover Complex

Domain wall motion is detected for the first time during the transition to a ferroelastic and spin state ordered phase of a spin crossover complex. Single-crystal X-ray diffraction and resonant ultrasound spectroscopy (RUS) revealed two distinct symmetry-breaking phase transitions in the mononuclear Mn³⁺ compound [Mn(3,5-diBr-sal₂(323))]BPh₄, 1. The first at 250 K, involves the space group change Cc→Pc and is thermodynamically continuous, while the second, Pc→P1 at 85 K, is discontinuous and related to spin crossover and spin state ordering. Stress-induced domain wall mobility was interpreted on the basis of a steep increase in acoustic loss immediately below the the Pc-P1 transition     

A new zirconium inorganic building brick forming metal organic frameworks with exceptional stability

Porous crystals are strategic materials with industrial applications within petrochemistry, catalysis, gas storage, and selective separation. Their unique properties are based on the molecular-scale porous character. However, a principal limitation of zeolites and similar oxide-based materials is the relatively small size of the pores, typically in the range of medium-sized molecules, limiting their use in pharmaceutical and fine chemical applications. Metal organic frameworks (MOFs) provided a breakthrough in this respect. New MOFs appear at a high and an increasing pace, but the appearances of new, stable inorganic building bricks are rare. Here we present a new zirconium-based inorganic building brick that allows the synthesis of very high surface area MOFs with unprecedented stability. The high stability is based on the combination of strong Zr-O bonds and the ability of the inner Zr6-cluster to rearrange reversibly upon removal or addition of mu3-OH groups, without any changes in the connecting carboxylates. The weak thermal, chemical, and mechanical stability of most MOFs is probably the most important property that limits their use in large scale industrial applications. The Zr-MOFs presented in this work have the toughness needed for industrial applications; decomposition temperature above 500 degrees C and resistance to most chemicals, and they remain crystalline even after exposure to 10 tons/cm2 of external pressure.     

Strontium d‐glutamate hexa­hydrate and strontium di(hydrogen l‐glutamate) penta­hydrate

[Sr(C₅H₇NO₄)]·6H₂O, (I), and [Sr(C₅H₈NO₄)₂]·5H₂O, (II), both crystallize with similar strontium–glutamate–water layers. In (I), the neutral layers are connected through hydrogen bonds by water mol­ecules, while in (II), the positively charged layers are connected through hydrogen bonds and electrostatic inter­actions by inter­leaving layers of hydrogen glutamate anions and water mol­ecules.     

Restrictions and expansions of holomorphic representations

We compute tensor products of representations of the holomorphic discrete series of a Lie group G, or restrictions to some subgroup G′. A detailed study is done for the case of the conformal group O(4, 2).