Chemometric evaluation of the column classification system during the pharmaceutical analysis of lamotrigine and its related substances

This paper investigates the performance of a column classification system developed at the Katholieke Universiteit Leuven applied to pharmaceutical chromatographic analyses. The liquid chromatography assay of lamotrigine and related compounds was carried out according to the method prescribed in the European Pharmacopoeia monograph, using 28 brands of stationary phases. A ranking was built based on the F _KUL value calculated against the selected reference column, then compared with the column test performance established for the stationary phases studied. Therefore, the system suitability test prescribed by the European Pharmacopoeia in order to distinguish between suitable or unsuitable columns for this analysis was evaluated. Moreover, it was examined whether the classes of the stationary phases, determined using test parameter results, contain either suitable or unsuitable supports for the lamotrigine separation. This assay was performed using chemometric a technique, namely factor analysis.

Hydroconversion of parafine LTP56-H over nickel/Na-mordenite catalysts

Nickel catalysts supported on Na-mordenite were used for paraffin LTP56-H hydroconversion into liquid material as a possible component for engine fuels. The effects of none-catalytic thermal treatment and catalytic conditions-zeolite type and reaction conditions (solvent) on the process of liquefaction of LTP56-H paraffin and physicochemical properties of catalysts were studied. The physicochemical properties of catalytic systems were investigated using XRD, TPR, TPD-NH3 and SEM-EDS methods.      

Physicochemical Insight into Coordination Systems Obtained from Copper(II) Bromoacetate and 1,10-Phenanthroline

Two different coordination compounds of copper were synthesized from the same building blocks (1,10-phenanthroline, bromoacetate anions, and copper cations). The synthesis parameters were carefully designed and evaluated to allow the change of the resulting compounds molecular structure, i.e., formation of mononuclear (bromoacetato-O,O’)(bromoacetato-O)aqua(1,10-phenanthroline-N,N’)copper(II) and dinuclear (μ-bromido-1:2κ²)bis(μ-bromoacetato-1κO,2κO’)bis(1,10-phenanthroline-N,N’)dicopper(II) bromoacetate bromoacetic acid solvate. The crystal, molecular and supramolecular structures of the studied compounds were determined and evaluated in Hirshfeld analysis. The UV-Vis-IR absorption and thermal properties were studied and discussed. For the explicit determination of the influence of compounds structure on radiation absorption in UV-Vis range, density functional theory and time-dependent density functional theory calculations were performed.     

The Callus of Phaseolus coccineus and Glycine max Biotransform Flavanones into the Corresponding Flavones

In vitro plant cultures are gaining in industrial importance, especially as biocatalysts and as sources of secondary metabolites used in pharmacy. The idea that guided us in our research was to evaluate the biocatalytic potential of newly obtained callus tissue towards flavonoid compounds. In this publication, we describe new ways of using callus cultures in the biotransformations. In the first method, the callus cultures grown on a solid medium are transferred to the water, the reaction medium into which the substrate is introduced. In the second method, biotransformation is carried out on a solid medium by growing callus cultures. In the course of the research, we have shown that the callus obtained from Phaseolus coccineus and Glycine max is capable of converting flavanone, 5-methoxyflavanone and 6-methoxyflavanone into the corresponding flavones.     

Gold and silver nanoparticles‐based laser desorption/ionization mass spectrometry method for detection and quantification of carboxylic acids

A comparison of ionization efficiency for gold and silver nanoparticles used as an active media of matrix‐less laser desorption/ionization (LDI) mass spectrometry (MS) methods was made for carboxylic acids including fatty acids. The matrix‐assisted laser desorption/ionization (MALDI)‐type targets containing monoisotopic cationic ¹⁰⁹Ag nanoparticles (¹⁰⁹AgNPs) and Au nanoparticles (AuNPs) were used for rapid MS measurements of 10 carboxylic acids of different chemical properties. Carboxylic acids were directly quantified in experiments with 10 000‐fold concentration change conditions ranging from 1 mg/ml to 100 ng/ml which equates to 1 μg to 100 pg of carboxylic acids per measurement spot.     

Controlling Single Molecule Conductance by a Locally Induced Chemical Reaction on Individual Thiophene Units

Among the prerequisites for the progress of single‐molecule‐based electronic devices are a better understanding of the electronic properties at the individual molecular level and the development of methods to tune the charge transport through molecular junctions. Scanning tunneling microscopy (STM) is an ideal tool not only for the characterization, but also for the manipulation of single atoms and molecules on surfaces. The conductance through a single molecule can be measured by contacting the molecule with atomic precision and forming a molecular bridge between the metallic STM tip electrode and the metallic surface electrode. The parameters affecting the conductance are mainly related to their electronic structure and to the coupling to the metallic electrodes. Here, the experimental and theoretical analyses are focused on single tetracenothiophene molecules and demonstrate that an in situ‐induced direct desulfurization reaction of the thiophene moiety strongly improves the molecular anchoring by forming covalent bonds between molecular carbon and copper surface atoms. This bond formation leads to an increase of the conductance by about 50 % compared to the initial state.     

Influence of the alkyl chain length of some mesogenic molecules on their Langmuir film formation ability

Langmuir films of members of two homologous series, the 4‐n‐alkyl‐4′‐cyanobiphenyls (nCB) for n = 2–14 and trans‐4‐n‐alkyl(4′‐cyanophenyl)cyclohexanes (PCHn) for n = 2–12, have been studied by recording surface pressure/area isotherms and by Brewster angle microscopy. It has been found that the compounds with very short chains (n3) and very long chains (n>12 for nCB, n>10 for PCHn) are unable to form compressible monolayers at the air–water interface. Other members of both series can form stable Langmuir films, but both their rigidity and stability as well as the molecular packing vary with the alkyl chain length. The isotherms and BAM images imply that the organization of the liquid crystal molecules in the films is to some extent correlated with their ability to form corresponding mesophase in the bulk: nematogenic compounds tend to form rounded droplet‐like domains, whereas smectogenic compounds tend to form flat domains.     

Dynamics in ferro- and antiferroelectric phases of a liquid crystal with fluorinated molecules as studied by dielectric spectroscopy

For 1-[3-fluoro-4-(1-methylheptyloxycarbonyl)phenyl]-2-[4-2,2,3,3,4,4,4-heptafluorobutoxybutoxy)biphenyl-4-yl]ethane (1F7), built of chiral molecules, results of dielectric measurements of liquid-crystalline and solid phases are presented. Rich polymorphism of liquid-crystalline (SmC*, SmC*_A and SmI*_A) phases as well as of solid (Cr1 and Cr2) phases were observed down to –130°C. At a frequency range from 0.1 Hz to 3 MHz, the relaxation processes were detected in ferroelectric SmC*, antiferroelectric SmC*_A and highly ordered SmI*_A smectic phases. The mechanism of complex dynamics (moleculear and collective) was identified with the help of the bias field. Vitrification of conformationally disordered crystal phase Cr2 was found in accordance with calorimetric observations.     

Determination of alkylphenols and their short-chained ethoxylates in Polish river waters

A simple and robust analytical method for analysis of octyl- and nonylphenol as well as their short-chained ethoxylates in river water was proposed. Quantification of these analytes was performed by high-performance liquid chromatography with fluorescence detection after isolation using solid phase extraction with polytetrafluoroethylene sorbent. The method allowed one to obtain about 80–100% recovery for octylphenol and its ethoxylates and 70–80% for nonylphenol and its ethoxylates. Also, there was no need for additional sample cleaning before chromatographic analysis. The limit of detection was 0.01?µg?L^?1 for octylphenol and its ethoxylates and 0.03?µg?L^?1 for nonylphenol and its ethoxylates. The proposed method was used for quantitation of octyl- and nonylphenol together with their short-chained ethoxylates. Nonylphenol, nonylphenol mono- and diethoxylates were detected at concentrations ranging from 0.12 to 0.53?µg?L^?1. Octylphenol, octylphenol mono- and diethoxylates were detected in four out of eleven samples at concentrations ranging from 0.03 to 0.17?µg?L^?1. High concentrations of nonylphenol and its ethoxylates were found in the samples, despite the fact that their use in European countries was forbidden several years ago.     

Electromagnetic simulations of tunable terahertz metamaterial infiltrated with highly birefringent nematic liquid crystal

In this article electromagnetic simulations of tunable terahertz metamaterial infiltrated with nematic liquid crystal are described. A full-wave analysis technique based on the finite-difference time-domain (FDTD) method was done by employing QuickWave 3D electromagnetic solver. Scattering parameter analysis shows a resonant frequency shift of 0.8 THz obtained by reorienting the layered highly birefringent nematic liquid crystal. Effective refractive index for operation frequency varies from negative to positive values.