Direct immersion solid-phase microextraction has been optimized and applied to the simultaneous determination of the neutral and basic pharmaceuticals: caffeine, carbamazepine, clomipramine, chlorprothixene and clotrimazole at low concentrations in municipal wastewater. Two absorption type stationary phases: polydimethylsiloxane (PDMS) and polyacrylate (PA) have been found to be most effective for extraction of target analytes. The separation and detection were carried out by gas chromatograph coupled with mass spectrometer working in the selected ion monitoring mode. The method was validated for linearity, detection and quantitation limits, selectivity and precision. The average correlation coefficient of the calibration curves was 0.9933. The LOD values in influent and effluent wastewater were in the range of 10–145 ng L?1 and 4–111 ng L?1, respectively, which were a bit higher than those in the deionized water due to matrix effect. The high values of distribution coefficient (Kfs) in PDMS/water and PA/water systems (log Kfs between 3.05 and 4.23) indicates the very high applicability of these stationary phases for determination of carbamazepine, clomipramine, chlorprothixene and clotrimazole in water samples.
Changes of total content of phenolic substances, alteration in total titratable acidity and differences in tartaric acid content in grapes of four white (Müller-Thurgau — MT, Pinot Blanc — Rulandské bílé in Czech, RB, Sauvignon (Sg), and Muscat Ottonel — Mu?kát Ottonel in Czech, MO) and two blue (Dornfelder — Df and Blue Frankish — Frankovka in Czech, Fr) grapevine varieties throughout their growth, ripening and maturing (July–November). Potentiometric titration was applied for the determination of total titratable acids in grapes (expressed as tartaric acid equivalents in g L?1). A spectrophotometric method according Rebelein based on the formation of a colored complex of ammonium metavanadate and tartaric acid was used for determination of tartaric acid in green juice made by pressing unripe grapes. A spectrophotometric method based on reduction of phosphomolybdato-tungsten complex in alkaline solution using Folin-Ciocalteau reagent was applied for determination of total content of phenolic substances (TCP).
New mesogens composed of achiral bent molecules with thermally stable ester linkages, and laterally substituted by a methoxy group symmetrically near the central benzene ring, were synthesized. Texture, calorimetric, electro‐optical, X‐ray and dielectric measurements were performed. In most of studied compounds the antiferroelectric B2 phase was found on cooling from the isotropic phase, followed by the B7 phase at lower temperatures. Undulation of layers in the B7 phase was confirmed by precise synchrotron studies. 相似文献
A photoinduced phase transition and helix untwisting in a new liquid crystal forming the SmC* phase were studied in detail. The compound consists of a cinnamoyl photosensitive fragment with C?=?C double bond capable of photoisomerisation and photocycloaddition. It was shown that ultraviolet (UV) irradiation (365 nm) induces an extreme decrease in phase transitions temperatures (SmC*–SmA*, SmA*–N*, N*–I). Vertically aligned samples in the SmC* phase cause selective light reflection in the visible spectral range. The light action results in a noticeable helix untwisting that causes a shift in the selective light reflection peak to the long-wavelength spectral region. The temperature dependence of spontaneous polarisation Ps was measured and it was found that UV irradiation induces a decrease in the values of Ps. Photo-optical phenomena taking place in the liquid crystal are attributed to the formation of photoproducts having low anisometry, which disrupts mesophases. 相似文献
The synthesis and thermotropic properties are reported for a series of hexaalkoxytriphenylenes that contain an amide, urea or thiourea group in one of their alkoxy tails. The intermolecular hydrogen bonding abilities of these molecules have a disturbing influence on the formation and stability of the columnar liquid crystalline phases. The stronger the hydrogen bonding the more the liquid crystallinity is suppressed, probably due to disturbance of the π–π stacking of the triphenylene discs. As a direct result, urea‐ and amide‐containing triphenylene derivatives are not liquid crystalline, but several thiourea derivatives show hexagonal columnar mesophases. 相似文献
We synthesized galactosyl chlorphenesin (CPN-G) using β-gal-containing Escherichia coli (E. coli) cells in which the conversion yield of chlorphenesin (CPN) to CPN-G reached about 64 % during 12 h. CPN-G was identified and characterized using high-performance liquid chromatography, liquid chromatography-mass spectrometry, Fourier transform-infrared spectrometry, and nuclear magnetic resonance analysis (1H and 13C). We verified that a galactose was covalently bound to a CPN alcohol group during CPN-G synthesis throughout these analyses. In particular, by the hydrolysis of CPN-G using β-gal, it was confirmed that a galactose was bound to CPN. The minimal inhibitory concentration (MIC) results showed that the CPN-G MICs were fairly similar to those of CPN. HACAT cell viability was significantly higher in CPN-G-treated cells than in CPN-treated cells at concentrations of 0.0–20.0 mM. Finally, we accomplished the synthesis of less toxic CPN-G, compared with CPN, using β-gal-containing E. coli cells as whole cells without changes in the MICs against microorganisms. 相似文献
An analytical method based upon the pressurised solvent extraction and gas chromatography and mass spectrometry (GC-MS) for analysis of nitrated derivatives of polycyclic aromatic hydrocarbons (nitro-PAHs) in roadside dust has been developed. Five nitro-PAHs (1-nitronaphthalene, 1-nitropyrene, 9-nitroanthracene, 2-nitrofluorene, 6-nitrochrysene) were chosen for this study because of their variable physical properties and effect on human health. Experiments with spiked inert matrix were used for the best extraction conditions finding. Different extraction conditions (temperature, pressure, solvents and duration of extraction cycle) were examined. The highest recoveries were observed at the extraction pressure of 14?MPa, temperature of 100°C and two cycles of 5?min extraction time, when dichloromethane was used as an extraction solvent. These conditions were applied to the extraction of nitro-PAHs from roadside dust. After extraction the nitro-PAHs fraction was isolated by the silica gel column chromatography. The GC-MS detector was used for analyses of the extracts. Recoveries of nitro-PAHs after extraction from roadside dust ranged from 60% for 9-nitroanthracene to 108% for 6-nitrochrysene. 相似文献
The objectives of this study were to evaluate the mobility of heavy metals (HMs) in two types of soils (acidic forest soil and neutral agricultural soil) by leaching with calcium chloride solution in column experiments. The screening properties of neutral agricultural soil towards pollution by heavy metals (Ni, Cu, Zn and Cd) are approximately 10 times higher than those of acid forest soil. The neutral agricultural soil, polluted artificially by one pore volume (PV) of an HMs solution of concentration 200 mg L?1, can screen the leaching of these metals over several hundreds of years. The higher apparent desorption rate and per cent desorption of HMs (especially Cd) in acid forest soil indicated a higher potential of intensive migration of the metals across the profile and indicated potential risk of Cd pollution for this type of soil. The latest approach of artificial neural networks to describe transport of HMs in soil has been also evaluated. Using a simple three-layer perceptron topology with three hidden neurons, the experimental data could be simulated. The results suggested that the pH of soil is a major factor controlling the retention of the heavy metals in the soils. 相似文献
Possibilities of a multicell isoperibolic-semiadiabatic calorimeter application for the measurement of hydration heat and maximum temperature reached in mixtures of various compositions during their setting and early stages of hardening are presented. Measurements were aimed to determine the impact of selected components?? content on the course of ordinary Portland cement (OPC) hydration. The following components were selected for the determination of the hydration behaviour in mixtures: very finely ground granulated blast furnace slag (GBFS), silica fume (microsilica, SF), finely ground quartz sand (FGQ), and calcined bauxite (CB). A commercial polycarboxylate type superplasticizer was also added to the selected mixtures. All maximum temperatures measured for selected mineral components were lower than that reached for cement. The maximum temperature increased with the decreasing amount of components in the mixture for all components except for silica fume. For all components, except for CB, the values of total released heat were higher than those for pure Portland cement samples. 相似文献
The reaction of propanedioic acid, 2-diazo-1,3-bis(1,1-dimethylethyl) ester (di-tert-butyl diazomalonate) with a series of cyclopenta[b]thiophenes in the presence of catalytic rhodium acetate was studied. The resulting S—C ylides underwent a rearrangement to form a heterocycle with different topology; thialene, in very low yields. Experimental and spectral data for all compounds are provided. 相似文献