Evaluation of a New LC Method for Analysis of Vancomycin Released from an Orthopaedic Drug Carrier System

Because of the increasing spread of antibiotic multiresistance, the drug vancomycin is a commonly used in orthopaedic surgery. The objective of our research was to develop a new method for analysis of the drug carrier systems—i.e. systems providing prolonged drug release—used in orthopaedics. The development of a pharmaceutical formulation requires a simple method for analysis of the active ingredient. For characterization of a drug release profile as a function of time, release of antibiotics from hydrophobic matrices was followed by in vitro tests. A rapid LC method, using a 2.1 mm × 150 mm, 5 μm particle, C₁₈ column and methanol–water–acetate buffer as mobile phase was developed for quantitative analysis of samples taken in drug release studies.

     

A new material for hydrogen storage; ScAl0.8Mg0.2

A novel aluminium rich alloy for hydrogen storage has been discovered, ScAl_0.8Mg_0.2, which has very promising properties regarding hydrogen storage capacity, kinetics and stability towards air oxidation in comparison to hydrogen absorption in state-of-the-art intermetallic compounds. The absorption of hydrogen was found to be very fast, even without adding any catalyst, and reversible. The discovered alloy crystallizes in a CsCl-type structure, but decomposes to ScH₂ and Al(Mg) during hydrogen absorption. Detailed analysis of the hydrogen absorption in ScAl_0.8Mg_0.2 has been performed using in situ synchrotron radiation powder X-ray diffraction, neutron powder diffraction and quantum mechanical calculations. The results from theory and experiments are in good agreement with each other.     

Measurement of one-bond heteronuclear dipolar coupling contributions for amine and diastereotopic methylene protons

One-bond heteronuclear and two-bond homonuclear residual dipolar couplings measured at methylene or amine sites can be utilized as long-range constraints in structure determination of molecules as well as to facilitate characterization of local conformation by stereospecific assignment of diastereotopic protons. We present two J-modulated HMQC type experiments to measure the one-bond heteronuclear dipolar coupling contributions of geminal protons individually. In addition two-bond homonuclear residual dipolar couplings between the diastereotopic protons are also obtained.     

Accurate measurement of long-range heteronuclear coupling constants from undistorted multiplets of an enhanced CPMG-HSQMBC experiment

Here, we present a modified CPMG-HSQMBC experiment which is capable to reduce the detrimental phase twists in the "long-range" connectivity multiplets caused by proton-proton couplings. We demonstrate that concerted CPMG pulse trains applied on both nuclei in the starting CPMG-INEPT transfer step can considerably be improved by composite pi pulses that compensate for pulse imperfections and off-resonance effects. Experimental optimization of the interpulse delay within the CPMG cycle was found to be crucial in order to achieve the best possible "decoupling" of homonuclear coupling modulation.     

Determination of imazalil by on-line coupled capillary isotachophoresis with capillary zone electrophoresis

A simple, rapid and reproducible capillary isotachophoretic on-line coupled with capillary zone electrophoresis (CITP-CZE) method for the determination of IMz in food packaging extracts and its residues in apples is described. A good separation of the IMZ from other sample constituents was achieved within 15 minutes without any sample clean up. Method characteristics (linearity, accuracy, intra-assay and detection limit) were determined. Less amount of time involved, sufficient sensitivity and low running cost are the important attributes of CITP-CZE method.     

LC-UV Assay of Tolperisone HCl from Sustained Release Matrix Tablets

Tolperisone HCl is a central muscle relaxant, which was incorporated in a matrix system formulated with poly(ethylene oxide)–PEO, in order to achieve adequate gastric residence time. This tablet presents considerable analytical difficulties in the quantitative determination of the drug, because the PEO matrix causes significant increase of viscosity in the samples. Our purpose was to develop a reproducible sample preparation method, which is adapted from parameters of the in vitro dissolution test and validate an LC-UV analytical method, which allows good recovery of the drug (99.97%). The developed analytical method was suitable for quantitative analysis of tolperisone HCl in matrix tablets.     

Facile Synthesis of Novel Selenium‐Containing Benzopyrans

4,4‐Dimethylchromeno[4,3‐d]selenadiazoles 8 with insecticide activities have been synthesized via oxidative ring closure of the corresponding semicarbazone derivatives 7 by treatment with selenium dioxide. Reaction of various alkoxy‐2,2‐dimethyl‐2H‐benzopyrans with phenylselenyl chloride was utilized to prepare different phenylselenyl‐ and 3‐chloro precocene analogs.     

Label-free immunosensor for monitoring vitellogenin as a biomarker for exogenous oestrogen compounds in amphibian species

A label-free, optical waveguide lightmode spectroscopy based immunosensor was developed for frog (Bombina orientalis) vitellogenin (Vtg) determination in biological samples as a biomarker for exogenous oestrogen compounds. Antibody against Vtg was produced in rabbits immunised with purified lipovitellin (Lpv), a precursor of Vtg, from the homogenised ovary of oriental fire-bellied toads (B. orientalis). The purified protein and Lpv/Vtg-specific serum were applied in both competitive and direct immunoassay formats using optical waveguide lightmode spectroscopy immunosensor. When measuring Vtg in direct manner, the Lpv antibody (1.76 µg mL^?1) was immobilised on the sensor surface, and the linear measuring range for Vtg was 0.1–10 µg mL^?1. During the competitive measurement, 100 ng mL^?1 Lpv was applied for the immobilisation. The linear measuring range for Vtg was 0.5–50 ng mL^?1. We studied the relative substrate specificity of the antibody, and it was concluded that the method is suitable for the sensitive and selective determination of Vtg levels in toads. Heart, liver and gonad samples from male animals were spiked with Vtg and were analysed using the newly developed method, and female toads and spawn samples were tested and compared to the calibration curve obtained by the spiked samples.     

Utilization of GDOES for the study of friction layers formed on the surface of brake discs during the friction process

The paper deals with the chemical characterization of friction layer, generated on the surface of friction materials during the friction test using the glow discharge optical emission spectrometry (GDOES). Friction layer is formed during the friction process and its character depends on several factors. One of the most important factors is the material composition of brake pads and brake disc. When the brake pressure is released at the end of the braking event, the specific friction layer remains on the surface of both pairs (brake pads and brake disc). Using the GDOES profile analysis, the thicknesses of friction layers were estimated and these results were compared with results obtained by scanning electron microscopy together with X-ray microanalysis.     

Reversible binding of metal ions onto bacterial layers revealed by protonation-induced ATR-FTIR difference spectroscopy

The ability of microorganisms to adhere to abiotic surfaces and the potentialities of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy have been exploited to study protonation and heavy metal binding events onto bacterial surfaces. This work represents the first attempt to apply on bacteria the recently developed method known as perfusion-induced ATR-FTIR difference spectroscopy. Such a technique allows measurement of even slight changes in the infrared spectrum of the sample, deposited as a thin layer on an ATR crystal, while an aqueous solution is perfused over its surface. Solutions at different pH have been used for inducing protonation/deprotonation of functional groups lying on the surface of Rhodobacter sphaeroides cells, chosen as a model system. The interaction of Ni(2+) with surface protonable groups of this microorganism has been investigated with a double-difference approach exploiting competition between nickel cations and protons. Protonation-induced difference spectra of simple model compounds have been acquired to guide band assignment in bacterial spectra, thus allowing identification of major components involved in proton uptake and metal binding. The data collected reveal that carboxylate moieties on the bacterial surface of R. sphaeroides play a role in extracellular biosorption of Ni(2+), establishing with this ion relatively weak coordinative bonds.