Volume 11, Issue 8

The ONIOM(B3PW91:HF) hybrid method has been evaluated for the purposes of modeling butyltin chlorides, XnSnCl4-n (X = n-butyl, sec-butyl, isobutyl, tert-butyl; n = 1, 2, 3). Three different partitioning schemes of a molecule within ONIOM(B3PW91:HF) were taken into account. For each of these partitioning schemes, conformational analyses of the XnSnCl4-n molecules were performed and then several molecular properties of the resulting rotamers were calculated. The values of molecular properties obtained by ONIOM(B3PW91:HF) were compared in a statistical manner with the reference values calculated by B3PW91. A careful choice of partitioning scheme for XnSnCl4-n allowed ONIOM(B3PW91:HF) to achieve a significant saving in computational cost, together with a relatively small decrease in the accuracy of the XnSnCl4-n molecular properties routinely obtained from conformational analysis (structural parameters, etc.). Unfortunately, the hybrid method turned out to be ineffective in reproducing the 1H, 13C and 119Sn NMR chemical shifts in XnSnCl4-n accurately.

On the basis of prior X-ray crystallographic results published by J. Janczak and G. Perpetuo, detailed vibrational studies were performed. The FT-IR and Raman spectra at ambient temperature were measured. The NLO properties were determined with the Kurtz-Perry experiment. Theoretical vibrational spectra were calculated. A detailed potential energy distribution (PED) analysis was performed. Assignments of observed bands were made. On the basis of these results, the behaviour of hydrogen bonds in the investigated compound was analysed and discussed. The equilibrium geometry of L-leucinium perchlorate was obtained. The results were compared with experimental X-ray data. The DFT formalism was used in theoretical studies. Detailed TDDFT study of hyperpolarizbility of first and second order for the investigated molecule was performed. Results were compared with experiments. Theoretical population analysis was used to determine the local electron density and local charges in investigated molecule. Differential scanning calorimetric study (DSC) was performed.

The synthesis of 3-deoxyoripavine (7) was realized as a novel and promising intermediate towards the synthesis of the important class of dopaminergic and/or serotonergic 10-deoxyaporphines and the special pharmacological tool µ opioid antagonist cyprodime. Generally, the preparation of these valuable biologically active compounds was achieved in remarkable yields.

An alternative method for extraction optimization of C18:2 n-6 and C18:3 n-3, the main precursors for the synthesis of conjugated linoleic acid (CLA), in Brachiaria ruzizienses forages was proposed. Three methods of lipid extraction were tested: 1. Hara & Radin, 2. Micro Folch and 3. Bligh & Dyer. The preliminary test showed the Hara & Radin method as the most promising procedure. Then, a 33 Box Behnken design with triplicate in the central point was applied in Hara & Radin method in order to optimize the extraction procedure. The optimization extraction was monitored by quantification of C18:2 n-6 and C18:3 n-3 through capillary zone electrophoresis (CZE). The results obtained by CZE were compared to gas chromatography (AOCS official method) in real samples using the paired t-test. No significant difference between methods was found within a 95% confidence interval (p-value= 0.937). The alternative CZE method for Brachiaria ruzizienses forages analysis has some advantages in comparison with official GC method such as, short analysis time (10 min), no derivatization step for sample preparation, absence of specific separation columns, lower analytical cost and high throughput.

Chromatographic properties of five steroid drugs: cortisone, hydrocortisone, methylprednisolone, prednisolone and norgestrel have been studied by normal-, reversed-phase and hydrophilic neutral cyano-bonded silica stationary phase with five binary mobile phases (acetonitrile-water, acetonitrile-DMSO, acetonitrile-methanol, acetone-petroleum ether, acetone-water) in which the concentration of organic modifier was varied from 0 to 100% (v/v). This study reports the optimization of steroid hormones separation. Chromatographic retention data and possible retention mechanisms are discussed. Separation abilities of mobile and stationary phases were studied using the principal component analysis method. The best separation of methylprednisolone and prednisolone is with a chromatographic system included silica gel as stationary phase and mixture of acetonitrile and DMSO (10:90 v/v). These two anti-inflammatory drugs can be fast separated from norgestrel when CN is used as stationary phase and acetone and water (40:60 v/v) as mobile phase. The highest values of the parameter Δ(ΔG°) and alfa for cortisone and hydrocortisone was observed in case of using CN as stationary phase and water-acetonitryle (40:60 v/v) as mobile phase.

In this study maltose, maltotriose and maltotetraose were for the first time, coupled to 4,4′-methylenedianiline (MDA). The aim of this preliminary work was to test the feasibility of oligo- and polysaccharide coupling to MDA and the characterization of the coupling products by high resolution mass spectrometry (MS). (+) nanoESI in combination with a quadrupole time of flight (QTOF) MS in full scan (MS) and MS/MS was optimized first on underivatized maltose, maltotriose and maltotetraose. The optimal screening and sequencing conditions were further applied to the MDA-functionalized oligosaccharides. The obtained results revealed a straightforward MS detection of the functionalized oligomers, high sequence coverage and a fragmentation pathway with the formation of B and Y ions as well as the complementary C and Z ions along with a typical cleavage of the aglycon. We consider that this methodology is fully applicable also to polydisperse mixtures of long chain polysaccharides, which due to the large number of components and their size require a systematic method of development and testing.

In the present study a reversed phase high performance liquid chromatography (RP-HPLC) method with diode array detector (DAD) at room temperature was used for obtaining impurity profiles of 20 drug products containing simvastatin as an active substance. Fourier-transform infrared spectroscopy (FT-IR) was carried out to obtain absorption spectra of samples. The partial least squares (PLS) model was built to predict the relative content of lovastatin, the main impurity of simvastatin, and sum of statin-like impurities. In order to build the PLS model, peak areas obtained from HPLC chromatograms were related to FT-IR spectra of drugs. The PLS model based on signal normal variate and orthogonal signal correction (SNV+OSC) transformed FT-IR spectra was able to predict the content of drug impurities in real samples with a good prediction ability (R2 > 0.95).

Nano-sized magnesium ferrites were synthesized by the sol-gel auto-combustion method using a variety of chelating/combustion agents: tartaric acid, citric acid, cellulose, glycine, urea and hexamethylenetetramine. The original purpose of this work was the synthesis of nano-sized magnesium ferrite by using, for the first time, cellulose and hexamethylenetetramine as chelating/combustion agents. Synthesized samples were subjected to different heat treatments at 773 K, 973 K and, respectively 1173 K in air. The disappearance of the organic phase and nitrate phase with the spinel structure formation was monitored by infrared absorption spectroscopy. Spinel structure, crystallite size and cation distribution were evaluated by X-ray diffraction data. The morphology of as-prepared powders was studied using scanning electron microscopy. The magnetic and dielectric properties were studied for the obtained samples.

This study is focused on the determination of some important antibiotics from different classes in waste water samples using solid phase extraction followed by high performance liquid chromatography with two detectors, diode array and mass spectrometer in positive ionisation mode. The investigated antibiotics include three penicillins (amoxicillin, ampicillin, penicillin G), two cephalosporins (ceftazidime, ceftriaxone), and two tetracyclines (tetracycline, doxycycline). The studied antibiotics were extracted from waste water samples using hydrophilic-lipophilic balanced cartridges. The extraction of antibiotics from water matrices was tested at several pH values. The best recoveries were obtained at pH 3 and 7 respectively. Depending on the nature of antibiotic, the limits of detection and quantification were obtained in the range of 0.07–0.92 µg mL−1 and 0.21–2.77 µg mL−1 respectively. Influent and effluent waste water samples were collected from a Waste Water Treatment Plant from Romania in order to detect the studied antibiotics. The antibiotics detected in the influent waste water samples were ceftriaxone (334 µg L−1), tetracycline (146 µg L−1) and doxycycline (110 µg L−1). In effluent waste water samples no target antibiotics were detected.

The first transition metal iodato peroxido complex, K3[V2O2(O2)4(IO3)]·H2O (I), was prepared by crystallization from the KVO3 — KIO3 — H2O2 — H2O — ethanol (HNO3) solution. The dinuclear anion is immediately decomposed in aqueous solution; the 51V NMR spectrum exhibits signals corresponding to [VO(O2)2(H2O)]−, [V2O2(OH)(O2)4]3− and H2VO4− species only. The IR and Raman spectra contain all characteristic bands of the VO(O2)2 group and the coordinated IO3− ligand. Based on the positions of bands assigned to the vibrations of the VO(O2)2 groups a pentagonal pyramidal arrangement around the vanadium atoms can be supposed. The crystal structure was solved from X-ray synchrotron powder data by direct space method and refined by energy minimization in the solid state employing a hybrid PBE0 functional. This crystal and molecular structure, has confirmed the presence of hexacoordinated vanadium atoms and revealed asymmetric dinuclear structure of the [V2O2(O2)4(IO3)]3− ion. The coordination spheres of vanadium atoms are different — the IO3− anion is coordinated only to one vanadium center. A thermal analysis of the complex confirmed the presence of water molecules in the crystal structure and revealed a considerable stability of the dehydrated complex.

The association process between two water soluble cationic porphyrins, 5,10,15,20-tetrakis[4-(trimethyl-ammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H2TTMePP) and 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine tetra-p-tosylate (H2TMePyP), as well as their Cu (II) complexes, with five series of nucleic agents has been studied using UV-VIS spectroscopy in aqueous solutions. During the titration with nucleic compounds the bathochromic effect of porphyrins absorption spectra can be observed as well as the hypochromicity of the Soret maximum. The association constants were calculated using a curve-fitting procedure (KAC of the order of magnitude of 103–105 mol−1). It has been shown that the interactions of H2TTMePP with nucleic agents are much stronger than interactions of H2TMePyP, which is most likely related to the kind and the size of the porphyrin substituent groups partaking in the process of stacking. The strength of the observed associated systems increases generally in a series: nucleic base

The production of surfactant from biological and renewable sources is important as this reduces environmental hazards since the products are highly biodegradable. Oil extracted from the seed of Luffa cylindrica using hexane in a soxhlet extractor was used in the synthesis of sodium phosphate-hydroxy ethanolamide via a simple reaction mechanism. The progress of the reaction was monitored and confirmed by FTIR, 1HNMR and 13CNMR. The process used gave a yield of 88.46% of sodium phosphate-hydroxy ethanolamide. The properties of this compound were compared with those of sodium dodecyl sulphate (SDS) used as a known reference surfactant. Important properties of sodium phosphate-hydroxy ethanolamide such as foam stability, wetting power and surface tension turned out superior to those of the known reference surfactant (SDS).

In the present work, the cobalt electrodeposition onto polycrystalline gold electrodes from aqueous solutions containing 0.01M CoSO4 + 1 M (NH4)2SO4 at pH=7 was analyzed. Linear voltammetry results suggested a change in the kinetic of the cobalt electrodeposition. In all cases, the nucleation rate (A), the number of active nucleation sites (N 0) and the saturation number of nuclei (N s ) values were potential dependent. The calculated Gibbs free energy (ΔG) for this system was 1.88×10−20 J nuclei−1 and the transfer coefficient for the Hydrogen Electroreduction Reaction (HER) was 0.47.

A simple and fast chemical method was used for synthesis of manganese tungstate nanoplates in flower-like clusters; while Taguchi robust design was employed as statistical method for optimization of the experimental parameters for the procedure. Ultrafine manganese tungstate plates in flower-like clusters were synthesized via a direct precipitation method involving addition of manganese ion solution to the aqueous tungstate reagent. Effects of various reaction conditions such as manganese and tungstate concentrations, flow rate of reagent addition and reactor temperature on the thickness of the synthesized manganese tungstate plates were investigated experimentally. Analysis of variance (ANOVA) showed that manganese tungstate nanoplates could be effectively synthesized by tuning significant parameters of precipitation procedure. Meanwhile, optimum conditions for synthesis of MnWO4 nanoplates via this simple, fast, and cost effective method were proposed. The structure and composition of the prepared nanoplates under optimum conditions were characterized by EDX, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), FT-IR spectroscopy, and photoluminescence techniques.