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131.
Tropane alkaloids solid-liquid extraction methods were developed and comprised ambient pressure ones: extraction with hot solvent, extraction at room temperature, on ultrasonic bath as well as pressurised liquid extraction (PLE) techniques. The highest yields of l-hyoscyamine in methanol PLE method (3 x 5 min, 110 degrees C) and scopolamine extracted with 1% tartaric acid in methanol (15 min, 90 degrees C) were determined. A mixed-mode reversed-phase cation-exchange solid-phase extraction (SPE) procedure was optimised for simultaneous recoveries of L-hyoscyamine, scopolamine, scopolamine-N-oxide from plant extracts as well as quaternary alkaloid representative: scopolamine-N-methyl bromide. First three alkaloids were efficiently eluted (recoveries 80-100%) from an Oasis MCX cartridge with methanol-10% ammonia (3:1, v/v) solution, whereas for the quaternary salt tetrahydrofuran-methanol-25% ammonia (6:1:3, v/v) was used with recoveries 52-6%. HPTLC-densitometric assay on silica gel plates was elaborated at 205 nm without derivatization and included: single development (over a distance 9.5 cm) with acetone-methanol-water-25% ammonia (85:5:5:8, v/v) mobile phase for L-hyoscyamine and scopolamine separation, whereas for scopolamine-N-oxide and scopolamine-N-methyl bromide a second development (to a distance 5.5 cm) with acetonitrile-methanol-85% formic acid (120:5:5, v/v) was applied. Newly elaborated RP-HPLC-diode array detection method was performed on Waters XTerra RP-18 column with gradient of acetonitrile in 15 mM ammonia solution and alkaloids were baseline separated within 20 min. Both chromatographic methods were validated and their quantitative results were compared. Good correlation between HPLC and HPTLC quantitative results was measured (correlation coefficients of mean values were 0.92086 and 0.99995 for L-hyoscyamine and scopolamine, respectively). In the RP-HPLC method, which was from 1.5- up to 7-fold more sensitive than HPTLC, limits of detection (LOD) and limits of quantitation (LOQ, in bracket) were (in ng/microl) as follows: 0.25 (0.82) for L-hyoscyamine, 0.29 (0.97) for scopolamine, 0.13 (0.45) for scopolamine-N-oxide and 0.58 (1.91) for scopolamine-N-methyl bromide. By the use of the optimised chromatographic methods, 14 various samples from the leaves and fruits of Datura sp. were screened for L-hyoscyamine and scopolamine contents and the most promising samples were established. 相似文献
132.
Kowalska E. Byszewski P. Diduszko R. Huczko A. Mieczkowski J. 《Journal of Thermal Analysis and Calorimetry》1998,54(1):197-202
The crystalline solvates containing fullerenes and (di)methylnaphthalenes were investigated by thermal analyses and X-ray
diffraction methods. It was found that C60 with (di)methylnaphthalenes forms two types of stable solvates: either at the molar ratio 1:2 decomposing at temperatures
close to 100°C or at 1:1 molar ratio decomposing in the temperature range 120–214°C. Crystalline lattice and thermal stability
of the solvates depends on the structure of the solvent molecules. The strong solute-solvent interaction is also manifested
by the modification of the C60 absorption spectra in solution. The results are discussed using semiempirical quantum chemistry methods.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
133.
Neugart R Balabanski DL Blaum K Borremans D Himpe P Kowalska M Lievens P Mallion S Neyens G Vermeulen N Yordanov DT 《Physical review letters》2008,101(13):132502
The electric quadrupole moment and the magnetic moment of the 11Li halo nucleus have been measured with more than an order of magnitude higher precision than before, |Q| = 33.3(5) mb and mu = +3.6712(3)muN, revealing a 8.8(1.5)% increase of the quadrupole moment relative to that of 9Li. This result is compared to various models that aim at describing the halo properties. In the shell model an increased quadrupole moment points to a significant occupation of the 1d orbits, whereas in a simple halo picture this can be explained by relating the quadrupole moments of the proton distribution to the charge radii. Advanced models so far fail to reproduce simultaneously the trends observed in the radii and quadrupole moments of the lithium isotopes. 相似文献
134.
S. George K. Blaum M. Block M. Breitenfeldt M. Dworschak F. Herfurth A. Herlert M. Kowalska M. Kretzschmar E. Minaya Ramirez D. Neidherr S. Schwarz L. Schweikhard 《International journal of mass spectrometry》2011,299(2-3):102-112
Collisions of ions with residual gas atoms in a Penning trap can have a strong influence on the trajectories of the ions, depending on the atom species and the gas pressure. We report on investigations of damping effects in time-of-flight ion-cyclotron resonance mass spectrometry with the Penning trap mass spectrometers ISOLTRAP at ISOLDE/CERN (Geneva, Switzerland) and SHIPTRAP at GSI (Darmstadt, Germany). The work focuses on the interconversion of the magnetron and cyclotron motional modes, in particular the modification of the resonance profiles for quadrupolar excitation due to the damping effect of the residual gas. Extensive experiments have been performed with standard and Ramsey excitation schemes. The results are in good agreement with predictions obtained by analytical continuation of the formulae for the undamped case. 相似文献
135.
One effective solution in the analysis of complex mixtures, including protein or cell hydrolysates, is based on chemoselective derivatization of a selected group of compounds by using selective tags to facilitate detection. Another method is based on the capture of the desired compounds by properly designed solid supports, resulting in sample enrichment. Cysteine is one of the rarest amino acids, but at least one cysteine residue is present in more than 91% of human proteins, which clearly confirms its important role in biological systems. Some cysteine-containing peptides may serve as significant molecular biomarkers, which may emerge as key indices in the management of patients with particular diseases. In the current review, we describe recent advances in the development of cysteine-containing peptide modification techniques based on solution and solid phase derivatization and enrichment strategies. 相似文献
136.
Anna Zbikowska Malgorzata Kowalska Katarzyna Zbikowska Sylwia Onacik-Gür Urszula empicka Pawe Turek 《Molecules (Basel, Switzerland)》2022,27(4)
According to international health and food organizations and authorities, people should limit fat intake since fat is the most caloric component of food and it is often a source of unsafe saturated fatty acids (FA) and trans isomers. The greatest health benefits come from replacing shorts with dietary fiber molecules. The aim of the study was to determine the possibility of reducing shortening content, which has an undesirable profile of FA, by addition of β-glucan molecules in shortbread biscuits. The effect of oat and yeast β-glucan supplementation on physical and sensory quality of products with reduced fat content (max 15%) were studied. It was shown that the substitution of shortening by β-glucan in shortbread biscuits is possible to a limited extent. Reduction in product energy value (up to 36 kcal/100 g) and content of undesirable FA (maximum 2.1 g/100 g) and increased of β-glucan content, regardless of the type, caused deterioration of biscuits quality and affected changes during storage. The substitution of shortening by β-glucan in food is a good way to improve nutritional value by increasing the amount of dietary fiber molecules, reducing calories, and amount of SFA in diets. 相似文献
137.
Nadja Frömmgen Dimiter L. Balabanski Mark L. Bissell Jacek Bieroń Klaus Blaum Bradley Cheal Kieran Flanagan Stephan Fritzsche Christopher Geppert Michael Hammen Magdalena Kowalska Kim Kreim Andreas Krieger Rainer Neugart Gerda Neyens Mustafa M. Rajabali Wilfried Nörtershäuser Jasna Papuga Deyan T. Yordanov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2015,69(6):164
138.
Godziek Agnieszka Maciejowska Anna Talik Ewa Sajewicz Mieczysław Kowalska Teresa 《平面色谱法杂志一现代薄层色谱法》2015,28(2):144-151
JPC – Journal of Planar Chromatography – Modern TLC - Spontaneous oscillatory chiral conversion and condensation of low-molecular-weight chiral carboxylic acids have been investigated... 相似文献
139.
Comparison of mouse plasma and brain tissue homogenate sample pretreatment methods prior to high‐performance liquid chromatography for a new 1,2,4‐triazole derivative with anticonvulsant activity 下载免费PDF全文
Jolanta Flieger Anna Kowalska Magdalena Pizoń Tomasz Plech Jarogniew Łuszczki 《Journal of separation science》2015,38(12):2149-2157
The focus of the study was to develop a bio‐analytical assay for a 1,2,4‐triazole derivative from plasma and brain tissue homogenate samples. The goal was to compare analytical techniques that facilitate high accuracy with simplified sample processing. In this study, commonly used standard protein precipitation and solid‐phase extraction methods utilizing C18 and cartridges of Hybrid technology were compared in terms of their ability for sample pretreatment and removal of biological matrices before high‐performance liquid chromatography quantification. Fast classical reversed‐phase chromatography on a C18 column paired with selective sample preparation using Hybrid solid‐phase extraction technology resulted in the most precise bio‐analytical determination of the hydrophobic 1,2,4‐triazole derivative in both biological samples studied. The obtained recovery values were above 95% with the coefficient of variation lower than 5%. 相似文献
140.
E. Kowalska P. Kowalczyk J. Radomska E. Czerwosz H. Wronka M. Bystrzejewski 《Journal of Thermal Analysis and Calorimetry》2006,86(1):115-119
Carbon nanotubes (CNTs) were synthesized using a chemical vapour deposition
(CVD) method. The properties of CNTs before and after vacuum annealing treatment
were studied using scanning electron microscopy (SEM), scanning tunneling
microscopy/spectroscopy (STM/STS) and thermogravimetric analysis (TG). Field
emission characteristics of the raw and vacuum heated (up to 650°C) carbon
nanotube films (CNTFs) were measured in a diode system. Emissive properties
of the CNTFs depend on an annealing process during which structural changes
in the nanotube walls take place. The structural changes, related to saturation
of dangling bonds, influence a rate of oxidation process and also improve
the emissive field properties. 相似文献