Determination of levofloxacin,ciprofloxacin, moxifloxacin and gemifloxacin in urine and plasma by HPLC–FLD–DAD using pentafluorophenyl core–shell column: Application to drug monitoring

Concentrations of fluoroquinolones, which are used in the treatment of many bacterial infections, should be monitored in biological fluids as they exhibit concentration-dependent bactericidal activity. In this study, a liquid chromatography method for the determination of levofloxacin, ciprofloxacin, moxifloxacin and gemifloxacin in human urine and plasma was developed for the first time. The efficiency of five different columns for the separation of these fluoroquinolones was compared. Experimental parameters that affect the separation, such as percentage of organic solvent, pH, temperature, gradient shape and detector wavelength, were optimized by a step-by-step approach. Using a pentafluorophenyl core–shell column (100 × 4.6 mm, 2.7 μm), the separation of four analytes was accomplished in <7.5 min. The developed method was validated for the determination of analytes in both urine and plasma with respect to sensitivity, specificity, linearity (r ≥ 0.9989), recovery (79.46–102.69%), accuracy, precision and stability (85.79–111.07%). The intra- and inter-day accuracies were within 89.55–111.94% with relative standard deviations of 0.35–8.05%. The feasibility of method was demonstrated by analyzing urine and plasma samples of patients orally receiving levofloxacin, ciprofloxacin or moxifloxacin. The developed method is suitable for therapeutic drug monitoring of these fluoroquinolones and can be applied to pharmacokinetic and toxicological studies.     

The Combination of Cross-Hyperconjugation and σ-Conjugation in 2,5-Oligosilanyl Substituted Siloles

Reaction of a 2,5-dilithiated silole with excess dichlorodimethylsilane gives the respective 2,5-bis(chlorodimethylsilyl) substituted silole. This compound can be converted to 2,5-bis(oligosilanyl) substituted siloles by addition of a suitable oligosilanide. In the UV spectra of the thus obtained compounds the lowest energy absorptions are bathochromically shifted compared to the absorptions of the two constituents, namely the 2,5-disilyl substituted silole and a trisilane. The bathochromic shift is interpreted as being caused by a mixed σ-conjugation/cross-hyperconjugation. This assumption is supported by TD-DFT calculations, which show a significant contribution from Si−Si bonds to the HOMO of the molecule.     

Genotypic variability for carbon isotope discrimination in the mutant and improved lines of barley

Drought tolerance is an important breeding objective in dry and semi-dry conditions. Carbon isotope discrimination (Delta) is a tool that may be used to improve water-use efficiency (WUE) as an indirect selection criterion. The study investigated the variability for Delta in improved F7 lines and their parents (three cultivars and two mutant lines), which were sampled randomly from an F6 nursery performing well under semi-dry conditions. In total, 40 entries were grown in sand culture, arranged in three-replicated randomized complete block designs in two sets of experiments in Antalya, Turkey. There were statistically significant differences (p<0.01) among genotypes in both sets of experiments for Delta, and Delta values range from 20.14 to 21.86. Low coefficient of variation (C.V.) values, i.e. 2 and 1.65 %, for both data sets revealed efficient control of experimental error for Delta and indicated little effect of environment. Consequently, broad-sense heritability estimates for Delta were 0.63 and 0.74. As Delta showed a considerably high heritability and consistency over the two sets of experiments and low C.V. values, it was concluded that this trait could be used in breeding programmes aimed at developing drought tolerance lines. The early heading mutant, M-K-88, and the cultivar selected from land race, Tokak 157-37, showed lowest Delta values, indicating that they had the best water-use efficiency. Low Delta values of these two genotypes were inheritable.     

Evidence for direct mechanism in the128Te(n,γ)129Te reaction at thermal neutron energies

The importance of surface effects on nuclear level densities is stressed and numerically estimated within the framework of the Thomas-Fermi model.     

Gas chromatographic analysis of methyldemeton

Summary A gas chromatographic method is described for the analysis of methyldemeton present in the form of two isomers,O,O-dimethyl O-2-(ethylthio)ethylphosphorothioate andO,O-dimethyl S-2(ethylthio)ethylphosphorothioate in mixtures containg benzene, xylene, 3-thiapentanol-1, andO,O,O-trimethylthiophosphate. Such mixtures are obtained when methyldemeton is synthesized fromO,O-dimethylchlorothiophosphate and 3-thiapentanol-1 [1]. The best results are obtained using a short stainless steel column packed with 5% (w/w) OV-17 on Chromosorb G AW-DMCS 100–120 mesh.     

Phenolic profiles of Serbian autochthonous variety ‘Prokupac’ and monovarietal international wines from the Central Serbia wine region

Phenolic profiles of young monovarietal white and red wines from the Central Serbia were investigated. Quantification of phenolics was done using ultra-high-performance liquid chromatography (UHPLC) coupled with a diode array detector and a triple-quadrupole mass spectrometer. Generally, red wines were characterised with higher phenolics content when compared to the white wines. This applies also for the total phenolics content (TPC) and radical scavenging activity (RSA) values. Among all the samples, the red wine from autochthonous Serbian variety ‘Prokupac’ stood out with unique composition, showing the highest TPC, RSA and the highest concentration of the individual phenolics. Finally, based on a specific phenolic pattern, principal component analysis (PCA) indicated clustering of red and white wines, with the ‘Prokupac’ as a prominent outlier.     

Structural characterization of a sodium perchlorate−acridino-18-crown-6 ether complex

This paper describes the X-ray crystal structure of a complex of acridino-18-crown-6 ether (S,S)-2 and sodium perchlorate. The structure shows a homodimer in the crystal and suggests the potential for π–π bonded interactions between the monomers. The average distance of the two tricyclic units (3.49 ± 0.1 Å) may indicate a considerably strong π–π interaction. Fluorescence titration was performed in order to determine the stoichiometry and stability constant (K _s) of the sodium ion-(S,S)-2 complex. Based on the global fitting of the fluorescence spectra, we suggest the formation of a complex with 1:1 ligand to metal ion ratio, and the logK value determined by nonlinear regression analysis was 5.23.     

Separation,Preconcentration and Spectrophotometric Determination of Rhodamine B in Industrial,Cosmetic and Water Samples by Cloud Point and Solid Phase Extraction

The aim of this study is extraction, preconcentration and spectrophotometric determination of Rhodamine B (RB) in aqueous media by developing solid phase extraction (SPE) and cloud point extraction (CPE) methods. Amberlite XAD-1180 adsorbent and Tergitol NP-7 surfactant were used for SPE and CPE, respectively. Parameters of SPE and CPE which effected quantitative extractions were investigated and optimized. Matrix effects of some ions and dyes were analyzed at the optimum conditions. Developed methods were used to determine RB contents of anti-freeze, lipstick and water samples. The results of both methods demonstrated that the RB was quantitatively extracted and determined. RB contents of solid samples were found between 473 ± 15 and 317 ± 8 μg/g; 472 ± 11 and 312 ± 6 μg/L dye contents were determined for liquid samples. The methods were tested by analysis of spiked samples. Analytical characteristics of the methods were compared with each other and previously reported studies.