Determination of therapeutic and toxic concentrations of doxepin and loxapine using gas-liquid chromatography with a nitrogen-sensitive detector, and gas chromatography-mass spectrometry of loxapine

A gas-liquid chromatographic procedure is presented for the determination of therapeutic and toxic serum levels of doxepin and loxapine, using a nitrogen-phosphorus-sensitive detector. Amitriptyline is used as the internal standard. The method is accurate, sensitive and specific with no derivatization required prior to analysis. An advantage of the procedure is the small serum sample size needed for analysis and the selectivity and sensitivity of the detector, with the limit of detection being 3 and 2 microgram/l for doxepin and loxapine, respectively. Nine cases of doxenin and loxapine misuse are presented. Serum doxepin concentrations ranged from 113 to 439 microgram/l, with a loxapine concentration of 192 microgram/l observed in one patient. The presence of the tricyclics was identified and confirmed by gas chromatography-mass spectrometry and the mass spectrum of loxapine is reported.     

The 16O(γ, po) reaction at intermediate photon energies

The ¹⁶O(γ, p_o) reaction has been investigated between photon energies E_γ = 40 and 105 MeV using a bremsstrahlung beam, full angular distributions being obtained at E_γ = 60, 80 and 100 MeV. While cross-section calculations which introduce a residual interaction of Yukawa form agree well with the data, the need for further work is indicated.     

Increasing the B/N ratio in boron nitride nanoribbons,a possible approach to dilute magnetic semiconductors

Density functional theory (DFT) employing the local spin density approximation and including correlation functionals is used to show that increasing the boron content relative to the nitrogen content in boron nitride nanoribbons can significantly reduce the band gap making the ribbons semiconducting. Armchair ribbons, but not zigzag ribbons, having excess borons are predicted to have a more stable optimized triplet structure than the optimized singlet structure. The triplet structure is predicted to have a higher density of states at the top of the valence band near Fermi level for the spin down state indicating it could be a ferromagnetic semiconductor. The results suggest a possible new approach to developing ferromagnetic semiconductors.     

Development of the Vinylogous Pictet–Spengler Cyclization and Total Synthesis of (±)‐Lundurine A

A novel vinylogous Pictet–Spengler cyclization has been developed for the generation of indole‐annulated medium‐sized rings. The method enables the synthesis of tetrahydroazocinoindoles with a fully substituted carbon center, a prevalent structural motif in many biologically active alkaloids. The strategy has been applied to the total synthesis of (±)‐lundurine A.     

Introducing a Cell-Free Approach for the Identification of Brewing Yeast (<Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>) Strains Using MALDI-TOF MS

Matrix-assisted laser desorption ionization (MALDI) time-of-flight mass spectrometry (TOF MS) is now accepted as a quick, easy-to-use, cost-effective, and accurate technique for the identification of microorganisms. However, the successful identification of microorganisms is dependent upon careful attention to factors such as growth conditions, extraction methods, mass spectral data collection, and data analysis procedures. Currently, most microorganism identification has been limited to the species level, and only a limited number of publications have been successful in achieving strain-level identification. In this work, a “cell-free” approach is introduced where peptide analytes secreted by several Saccharomyces cerevisiae strains during their growth period are analyzed. The analysis of the cell supernatant generates mass spectral patterns that are specific to each strain. The patterns generated in combination with a robust data analysis workflow using the open-source programs MALDIquant and Mass-Up allows for strain-level identification of S. cerevisiae. The cell-free approach using the yeast supernatant to accurately identify yeast strains is presented here as a proof of concept.

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Graphical Abstract

     

Trends in speciation analysis of vanadium in environmental samples and biological fluids--a review

A comprehensive review is presented addressing recent trends in the speciation and determination of vanadium in environmental and biological sample matrices, including important analytical aspects such as sample clean up, pre-concentration and method development. Methodology based on both separation and spectroscopic techniques for the determination of vanadium speciation is discussed. A brief outline of analytical principles, together with an overview of the recent developments and applications of vanadium speciation determination is included. The newer methods for detecting metal ions including hyphenated spectroscopic techniques and sample preparation schemes are also discussed.     

Facile control of silica nanoparticles using a novel solvent varying method for the fabrication of artificial opal photonic crystals

In this work, the Stöber process was applied to produce uniform silica nanoparticles (SNPs) in the meso-scale size range. The novel aspect of this work was to control the produced silica particle size by only varying the volume of the solvent ethanol used, whilst fixing the other reaction conditions. Using this one-step Stöber-based solvent varying (SV) method, seven batches of SNPs with target diameters ranging from 70 to 400 nm were repeatedly reproduced, and the size distribution in terms of the polydispersity index (PDI) was well maintained (within 0.1). An exponential equation was used to fit the relationship between the particle diameter and ethanol volume. This equation allows the prediction of the amount of ethanol required in order to produce particles of any target diameter within this size range. In addition, it was found that the reaction was completed in approximately 2 h for all batches regardless of the volume of ethanol. Structurally coloured artificial opal photonic crystals (PCs) were fabricated from the prepared SNPs by self-assembly under gravity sedimentation.

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The development of novel organically modified sol-gel media for use with ATR/FTIR sensing

The ability to prepare and develop novel pre-concentration media by the sol-gel process, and their integration with mid-infrared transparent waveguides has been demonstrated. This research approach resulted in a mid-infrared sensing methodology in which the properties (porosity, functionality, polarity, etc.) of the recognition layer could be tailored by variation of the sol-gel precursors and processing conditions. Cross-linker type and concentration notably influenced p-xylene absorption and diffusion rate. Unreacted silanol groups appeared to be the dominant factor in the hydrophobicity of sol-gel layers. Variation of sol-gel precursors and thermal treatment altered both film cross-link density and polarity, as demonstrated by variation in the rate of analyte diffusion and equilibrium analyte concentration. The use of a novel 1 : 1 PTMOS : DPDMS material as pre-concentration medium in this analytical sensing approach was validated through the determination of p-nitrochlorobenzene in an aqueous environment. The response demonstrated linearity between 0-30 mg L(-1) with a correlation coefficient of 0.989 and a limit of detection of 0.7 mg L(-1). Sensing times for p-nitrochlorobenzene were also reduced from several hours to 24 minutes, without loss of measurement accuracy or sensitivity, by a 10 degrees C increase in the sensing temperature and the use of a predictive Fickian model previously developed by this research group.