Application of umbelliferone molecularly imprinted polymer in analysis of plant samples

The molecularly imprinted polymers (MIPs) were synthesised and the influence of the type of porogen, the nature of sample solvent, and the binding capacity of material were tested by high-performance liquid chromatography (HPLC). Umbelliferone was used as the template for imprint formation. Methacrylic acid was used as the monomer and acetonitrile, ethanol, and chloroform as porogen. Non-imprinted polymers (NIPs) were prepared by the same procedure. The highest value of the specific binding capacity (269 μg of umbelliferone per 100 mg of polymer) was obtained for polymers prepared in chloroform as porogen and methanol/water (φ _r = 1: 1) as the sample solvent. The group-selective MIP was used as sorbent for the SPE pre-treatment of umbelliferone from plant extracts prior to HPLC analysis. Analysis of the spiked samples showed good recoveries (> 77 %). The limit of detection, limit of determination, and repeatability of the method were also calculated.     

Stereoselective total synthesis of protected sulfamisterin and its analogues

The stereoselective synthesis of sulfamisterin I and its unnatural analogues II and V in their protected form was achieved through a common strategy. The Wittig reaction of aldehydes VIII and IX with the C₁₄ hydrophobic side-chain X served as the key C-C connecting transformation. Subsequent functional group inter-conversions in the coupling products XI and XX completed the total synthesis.     

Methodological aspects of an off‐line combination of preparative isotachophoresis and high‐performance liquid chromatography with mass spectrometry in the analysis of biological matrices

This work reports on some methodological aspects of an off‐line combination of preparative ITP and HPLC with mass spectrometric detection (pITP‐HPLC‐MS) and its potential applications to the analysis of high molecular mass compounds present in complex biological matrices from the analytical chemistry perspective. Lysozyme served as the model analyte and human saliva as the complex biological matrix in this study. A mixture of five low‐molecular mass compounds was found and successfully used in the pITP experiments as discrete spacers to isolate the analyte from the interferents present in the complex biological matrix and to minimize their disturbance effect on the final MS analysis. The experiments at the pITP stage were performed in the cationic mode. On‐column conductivity detectors were used for the detection of ITP zones. Lysozyme was found in the human saliva samples using just deconvolution of the MS data after background correction. The MS data obtained from HPLC‐MS analysis of pITP fractions exhibited the great analytical potential of the combination of pITP‐HPLC‐MS resulting from the ITP clean‐up effect as well as the ITP preconcentration of the analyte present at low concentration levels in complex biological matrices.     

Pore Development during the Carbonization Process of Lignin Microparticles Investigated by Small Angle X-ray Scattering

Application of low-cost carbon black from lignin highly depends on the materials properties, which might by determined by raw material and processing conditions. Four different technical lignins were subjected to thermostabilization followed by stepwise heat treatment up to a temperature of 2000 °C in order to obtain micro-sized carbon particles. The development of the pore structure, graphitization and inner surfaces were investigated by X-ray scattering complemented by scanning electron microscopy and FTIR spectroscopy. Lignosulfonate-based carbons exhibit a complex pore structure with nanopores and mesopores that evolve by heat treatment. Organosolv, kraft and soda lignin-based samples exhibit distinct pores growing steadily with heat treatment temperature. All carbons exhibit increasing pore size of about 0.5–2 nm and increasing inner surface, with a strong increase between 1200 °C and 1600 °C. The chemistry and bonding nature shifts from basic organic material towards pure graphite. The crystallite size was found to increase with the increasing degree of graphitization. Heat treatment of just 1600 °C might be sufficient for many applications, allowing to reduce production energy while maintaining materials properties.     

Intensive 2-phenylethanol production in a hybrid system combined of a stirred tank reactor and an immersed extraction membrane module

Bioconversion of l-phenylalanine to 2-phenylethanol using Saccharomyces cerevisiae is connected with the growth of biomass strongly limited by product inhibition. Therefore, fermentation can proceed only at low conversions of l-phenylalanine with very low yield of the desired product, which allows reaching the maximum concentration of 2-phenylethanol, 4 g L^?1, in an ordinary batch, fed-batch, or chemostat bioreactor. To minimize capital and operating costs in the bioproduction of chemical specialties where the product inhibits the bioreaction, using a hybrid system based on the application of membrane extraction integrated in the bioreactor to remove the product is a suitable solution. Integration can be done by an external module for membrane extraction or, as a more efficient solution, by an extraction membrane module immersed directly in the bioreactor. Such a hybrid system can be used to remove 2-phenylethanol from the fermentation media and thus to overcome the product inhibition of the biotransformation process. In this paper, a hybrid system consisting of a stirred tank bioreactor (3.5 L) and an immersed extraction hollow fiber membrane module was studied. In the proposed system, the kinetics of 2-phenylethanol extraction from a water solution with and without biomass in the bioreactor to alkanes at different operational conditions was measured. Extraction kinetics was compared with the predictions obtained by a mathematical model. In the hybrid system, two extractive biotransformation experiments were performed and compared with that without product removal. Experimental data were also mathematically predicted with good accuracy between the simulation and the experiment.     

MR detection of mechanical vibrations using a radiofrequency field gradient

A new method for NMR characterization of mechanical waves, based upon radiofrequency field gradient for motion encoding, is proposed. A binomial B1 gradient excitation scheme was used to visualize the mobile spins undergoing a periodic transverse mechanical excitation. A simple model was designed to simulate the NMR signal as a function of the wave frequency excitation and the periodicity of the NMR pulse sequence. The preliminary results were obtained on a gel phantom at low vibration frequencies (0-200 Hz) by using a ladder-shaped coil generating a nearly constant RF field gradient along a specific known direction. For very small displacements and/or B1 gradients, the NMR signal measured on a gel phantom was proportional to the vibration amplitude and the pulse sequence was shown to be selective with respect to the vibration frequency. A good estimation of the direction of vibrations was obtained by varying the angle between the motion direction and the B1 gradient. The method and its use in parallel to more conventional MR elastography techniques are discussed. The presented approach might be of interest for noninvasive investigation of elastic properties of soft tissues and other materials.     

Dipole-dipole coupling constant for a directly bonded CH pair--a carbon-13 relaxation study

Multiple-field (4.7, 9.4, 14.1 T) carbon-13 relaxation data are reported for hexamethylenetetramine (HMTA) in the cryosolvent D(2)O/DMSO at 243 K. Under these conditions, the reorientational motion of HMTA is outside of the extreme narrowing range and the relaxation data can be subjected to a quantitative interpretation. Because of the high symmetry of the HMTA molecule, the reorientation must be isotropic. Treating the reorientation as a small-step rotational diffusion of a rigid body, we obtain a rotational correlation time of 1.0 ns and a carbon-proton dipole-dipole coupling constant corresponding to an effective internuclear distance of 114. 2 pm. The harmonic vibrational correction to the dipole-dipole coupling constant, based on a known force field, yields an NMR estimate of the r(alpha) distance of 110.8 +/- 0.3 pm.     

Lifetime measurements of lithiumD-states

We report lifetime measurements of the 1s ² 3d ² D, 1s ²4d ² D, and 1s ²2p ² P states of lithium. The results τ=14.5±0.7 ns, τ=31.0±1.0 ns, and τ=27.9±1.0 ns respectively were obtained by time resolved detection of the resonance fluorescence following pulsed laser excitation.     

Preparation and Photophysics of 2-(1-Pyrenyl)acrylic Acid and Its Methyl and 2′,2′,6′,6′-Tetramethyl-4′-Piperidyl Esters

Novel probes represented connection of pyrene as chromophore and sterically hindered amine stabilizers (HAS) in the form of esters of 2-(1-pyrenyl)acrylic acid were synthesized. HAS was in the form of parent amine (PAP) as well as stable nitroxyl radical form (PAP-NO^.). Photophysics of these probes were compared with their precursor as 2-(1-pyrenyl)acrylic acid (PAA) and its methyl ester (PAM). The fluorescence spectrum of PAA strongly depends on the acidity of the solution. The spectrum in neutral methanol indicates that it originates from the anionic form –COO⁻. Changes of acidity or basicity of methanol solution resulted in the changes of shape, position as well as the intensity of fluorescence band. This is due to the presence of protolytic equilibria, either in the ground state or in the singlet excited state, leading to the formation of molecular form –COOH and the cationic form –COOH₂⁺. The ester analogues did not show any changes in various pH conditions. Fluorescence of all probes depends on the polarity of solvents and the presence of oxygen. Intermolecular quenching was studied with external quenchers TEMPO and oxygen and the data were compared with the intramolecular quenching using 1′-oxo-2′,2′,6′,6′-tetramethyl-4′-piperidinyl-2-(1-pyrenyl)acrylate (PAP-NO^.).