Evaluation of the renal calculi compositions

Thermal analysis and infrared (IR) spectroscopy are modern physical–chemical methods suitable for the investigation of the kidney stones composition. The applications of these methods in our work were anticipated by performing the standard thermal analysis and standard infrared spectra on pure compounds: oxalates, phosphate, carbonate, and uric acid. This work reveals a logical algorithm for correlating the experimental data regarding urolithiasis types and compositions by thermal analysis methods, Fourier Transform Infrared (FT-IR) spectroscopy, and second derivative FT-IR spectra. The limits and performance of each analysis method have been highlighted, and by correlating the results of both methods we have obtained comprehensive information for the identification and/or determination of the main components as well as of organic and/or inert impurities in calculi composition. The data regarding the urinary calculi composition are important for the clinical guideline in the prophilaxy and methaphylaxy of urolithiasis.     

Simplification of determination method for standard materials using post-column reaction GC/FID

For the simple and fast preparation of highly reliable standard materials, a post-column reaction GC/FID system was developed and evaluated on the mixture of oxygen-containing organic compounds. The oxygen-containing organic compounds mixing solution were determined with the post-column reaction GC/FID system using n-dodecane as an internal calibration standard. Required value of relative expanded uncertainty as an original source of SI-traceable standard materials was within 1% and it aimed at this value as accuracy of the quantitative analysis. The results showed good agreement between the prepared concentrations and analytical values using post-column reaction GC/FID system. These results indicated that the post-column reaction GC/FID system would be used for getting SI-traceable values.     

New benchmark for basic and neutral nitrogen compounds speciation in middle distillates using comprehensive two-dimensional gas chromatography

This paper reports an analytical method for the comprehensive two-dimensional gas chromatography (GC x GC) separation and identification of nitrogen compounds (N-compounds) in middle distillates according to their types (basicity). For the evaluation of the best chromatographic conditions, a non-polar x polar approach was chosen. The impact of the second dimension (stationary phase and column length) on the separation of basic and neutral N-compounds was evaluated by mean of two-dimensional resolution. This study revealed that the implementation of polar secondary column having free electron pairs improves drastically the separation of N-compounds. Indeed, the presence of permanent dipole-permanent dipole interactions between neutral N-compounds and the stationary phase was enlightened. The comparison of two different nitrogen chemiluminescence detectors (NCD) was also evaluated for GC x GC selective monitoring of N-compounds. Owing to higher resolution power and enhanced sensitivity achieved using developed chromatographic and detection conditions, it was possible to identify univocally and to quantitate N-compounds (i) by class of compounds and (ii), within a class, by carbon number. Finally, quantitative comparison of GC x GC-NCD with conventional gas chromatography illustrates the benefits of GC x GC leading to an excellent correlation with results obtained by American Society for Testing Materials (ASTM) methods for the determination of basic/neutral nitrogen ratio in diesel samples.     

C-13 chemical shifts of the carbonyl group—VI: Transannular interactions in mesocyclic compounds

The utility of C-13 NMR in detecting transannular interactions of a carbonyl group with ? O? , ? S? and ? N? in eight-membered ring compounds has been studied. The C-13 carbonyl chemical shifts were determined in two solvents, employing frequency-sweep and pulse/Fourier transform techniques. The results confirm earlier conclusions based upon other physical methods and indicate that C-13 NMR should prove useful in studies of such interactions.     

气相色谱/氢火焰离子化检测法分析烷基化物料中的C4氟代烃

以实验室合成的氟代叔丁烷、氟代仲丁烷、氟代正丁烷为参考,建立了烷基化物料中C4氟代烃的气相色谱/氢火焰离子化检测(GC/FID)分析方法。提出了利用气相色谱/原子发射光谱(GC/AED)按元素响应的特点求算C4氟代烃在GC/FID上相对校正因子的方法。方法采用OV-225(50 m×0.25 mm i.d.×0.25 μm)和SE-54(44 m×0.22 mm i.d.×0.25 μm)串联柱为分析柱,FID为检测器,校正归一化或间接外标方法进行定量,具有重复性好、应用移植便利、操作简单等特点,对氟代叔     

Transferability in the natural linear-scaled coupled-cluster effective Hamiltonian approach: Applications to dynamic polarizabilities and dispersion coefficients

A natural linear-scaled coupled-cluster (CC) method has been developed to calculate the response properties of large molecules, for example, dynamic polarizabilities and dispersion coefficients. The method is based on the transferability of the CC effective Hamiltonian from the equation-of-motion (EOM)-CC methods, subject to its representation in terms of highly transferable natural localized molecular orbitals. This transferability allows the interactions among regions in a molecule to be classified according to their important inter-region excitations and de-excitations. Dynamic polarizabilities determined in this way provide insight into calculating the excited states of large molecules using localized orbital concepts. Dispersion coefficients for the interactions within large molecules can be similarly determined. These could be useful in constructing corrective long-range potentials. Applications to alkanes, tryptophan, and polyglycine are presented. For those cases which are possible, conventional results can be reproduced. Dynamic polarizabilities of tryptophan indicate that the first excited state is localized to the indole group, while the second is localized to the carboxyl group.     

Quantum-chemical method for determination of effective structure-energy parameters of multiparticle interaction in solutions of polar substances

A new method is developed for the determination of equilibrium value of effective structure-energy parameter of multiparticle interaction (Onsager radius of a molecule) in solutions of polar compounds. The method is based on the results of quantum-chemical calculations of the dependence of an electric dipole moment of the studied molecule in the ground state on the dielectric properties of the individual solvents that are applied. Additinal data were obtained that confirmed an opinion that by its physical sense the Onsager radius of a molecule was a value close to van der Waals radius of the same molecule which can be found using known methods of quantum chemistry and structural chemistry for isolated molecules (gas phase). It was shown by an example of solutions of 4-dimethylaminochalcone and several phthalimide and N-methylphthalimide derivatives that the results of determination of Onsager and van der Waals radii of all the studied molecules using three independent methods are in good quantitative agreement confirming their validity.     

NMR and ESR Investigation of Some Phosphorus Organic Compounds and their Free Radicals

Abstract

The new methods of NMR and ESR spectroscopy are developed for investigation of the properties and the character of intramolecular interactions for three and four coordinated phosphorous containing compounds. Analytical dependences of direct, geminal and vicinal constants of spin-spin coupling in NMR spectra upon geometrical parameters of molecules of the P=O, P=S, P=Se orientation for the cyclic phosphorous compounds are established.