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排序方式: 共有393条查询结果,搜索用时 15 毫秒
141.
In this study a new RP‐HPLC with photo‐diode array detection method for the determination of ibuprofen ((RS)‐2‐(4‐isobutylphenyl)propionic acid) in human plasma samples was developed. Samples were prepared by SPE and analyzed by an isocratic elution mode over a C18 column using 80% methanol. A novel sample pretreatment method, based on the addition of ionic liquids possessing chaotropic ions to small human plasma sample (100 μL), was elaborated. 1‐Butyl‐3‐methylimidazolium chloride and 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIM BF4) were tested from the point of view of extraction yield. Quantification was based on calibration curve applying diclofenac as the internal standard. Owing to dilution of plasma sample by 2 mM aqueous solution of BMIM BF4 before SPE, appropriate sample purification and extraction yields higher than 95% with precision lower than 2% can be achieved. Linear coefficients of correlation (r2) were >0.99 in the range of 0.3–5 μg/mL ibuprofen concentration in plasma. The limit of quantification was 65 ng/mL and the detection limit for ibuprofen was 19.5 ng/mL. 相似文献
142.
Jolanta Flieger Agata Siwek Magdalena Pizoń Anna Czajkowska‐Żelazko 《Journal of separation science》2013,36(9-10):1530-1536
This paper is devoted to application of ionic liquids as surfactants in LC of organic compounds, derivatives of 1,4‐thiosemicarbazides. According to HPLC requirements the most advantageous conditions such as transparency for ultraviolet light, low CMC, additional inorganic salt additives, and appropriate organic solvent were established. The CMC was determined using conductivity measurements. Suitability of two different stationary phases: RP‐C18 and cyanopropyl bonded phase was examined under micellar conditions. Chosen ionic liquid surfactant was compared to common traditional amphiphilic reagent – SDS. Elaborated on chromatographic micellar conditions were tested as a pilot technique for prediction of distribution coefficients of organic analytes in ionic liquid‐based aqueous two‐phase system. 相似文献
143.
Jolanta ?wiatowska Virginie LairCatarina Pereira-Nabais Gérard CotePhilippe Marcus Alexandre Chagnes 《Applied Surface Science》2011,257(21):9110-9119
Thin ceria layer deposited by electro-precipitation onto graphite was synthesised and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electro-precipitated ceria has a cubic structure with nanocrystallites of about 6 nm. The SEM analyses shows that the ceria layer reflects the morphology of the graphite electrode, exhibits small cracks usually found on the electro-precipitated films but covers almost completely the surface of the graphite. The ceria layer is composed of 75% Ce(IV) and 25% Ce(III) oxides as indicated by the XPS analyses. Cyclic voltammetry and galvanostatic charge-discharge tests in ethylene carbonate/dimethyl carbonate (1/1) (wt/wt) in the presence of 1 M LiPF6 show that reversible lithium insertion and deinsertion occurs in the graphite/ceria electrode and that the ceria layer on the graphite electrode prevents from the loss of capacity during the first four cycles. The reduction of the electrolyte occurs at about 0.7 V vs Li/Li+ on both electrodes but XPS and SEM analyses show that the SEI layer is thin and not as homogenous on the graphite as on the graphite/ceria electrode. The composition of the SEI layer on the graphite/ceria electrode, mainly composed of Li2CO3, ROCO2Li, R-CH2OLi and LiF, is different than those obtained on the graphite. 相似文献
144.
Rafa Jerzy Kopiasz Waldemar Tomaszewski Aleksandra Ku
miska Karolina Chreptowicz Jolanta Mierzejewska Tomasz Ciach Dominik Jaczewski 《Macromolecular bioscience》2020,20(7)
The antimicrobial properties of polycations are strongly affected by the structural features such as the backbone flexibility and topology (isomerism) through the polymer ability to attain proper conformation in interaction with the cell membrane. In this paper, a synthesis and biocidal properties evaluation of ionenes characterized by different backbone topology (isomerism) and flexibility are presented. The findings reveal influence of variation in topology on activity against different microorganisms, and general positive effect of improved flexibility. Furthermore, one of the obtained ionenes displays degradable properties in near physiological environment (phosphate‐buffered saline pH 7.4, 37 °C). The degradation proceeds via Hofmann elimination reaction and the products are not of acidic character. For the first time a new class of degradable ionenes with a high antimicrobial potential is presented. 相似文献
145.
Several selectively protected spermidine homologues were synthesized via cyanoethylation reaction of monoprotected diamines, subsequent protection of their secondary amino group, hydrolysis of nitrile to primary amide function, and final Hofmann degradation of amides to amines with the aid of iodosobenzene diacetate (PIDA). The protected spermidine homologues may be directly used in the synthesis of polyamine amides or may be further functionalized. 相似文献
146.
gem‐Chlorophenylcyclopropanes 3 are conveniently prepared by reaction of benzal chloride (1) with alkenes 2, carried out either in the presence of solid potassium hydroxide and 18‐crown‐6 as a catalyst or cesium hydroxide monohydrate, without solvent. 相似文献
147.
JPC – Journal of Planar Chromatography – Modern TLC - High-performance thin-layer chromatography (HPTLC) on silica gel 60 F254 TLC plates, with ethyl acetate-methanol-acetone-acetic... 相似文献
148.
Summary The CEC L-85-T-99 pressure differential calorimetry (PDSC) test was developed in Europe for ACEA E5 specification for heavy duty diesel oils. This test differentiate between base oils, additives, indicates synergies between antioxidants and correlates with other oxidation tests. Occasionally, the PDSC test can have difficulties to provide a true value for the OIT, which can vary between samplings. This work gives evidence of such case and concludes that variability in results is caused by variability in the oil rather than in the test itself. It appeared possible that certain oils might not be fully homogenous and this could produce a problem for representative PDSC sampling. 相似文献
149.
Experimental study of mixing time of non-Newtonian shear-thinning fluids within the transitional regime (3 × 102 < Re < 3 × 103) of liquid flow is presented. The purpose of this study was to analyze the effect of eccentricity and pumping mode of the
impeller as well as of position of the tracer dosage point into the agitated liquid on mixing time. The measurements were
conducted in an unbaffled agitated vessel with inner diameter D = 0.7 m equipped with an up-or down-pumping propeller located centrically (e/R = 0) or eccentrically (e/R ≠ 0) in the vessel. Experiments were carried out by means of computer-aided unsteady-state thermal method for three positions
of the tracer dosage point. The experimental data show that eccentric position of the propeller in an unbaffled vessel causes
a decrease of the mixing time compared to that obtained in a vessel with a centrically located propeller. Mixing time depends
also on the pumping mode of the propeller as well as on the position of the tracer dosage point.
Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May
2007. 相似文献
150.
Jolanta Wolska Krystyna Przepiera Hanna Grabowska Aleksander Przepiera Maciej Jabłoński Roman Klimkiewicz 《Research on Chemical Intermediates》2008,34(1):43-51
This paper reports the investigation ofC-alkylation of phenol with methanol over zinc ferrite as a catalyst. The reactions were carried out in gas phase at atmospheric
pressure in dependence of increasing temperature. The total selectivity towardsortho-cresol and 2,6-xylenol over 300°C surpassed 90%. ZnFe2O4 was obtained by oxidative precipitation method from solution of iron (II) sulphate and zinc sulphate at 60°C. Based on the
results, the best equation describing the oxidation reaction rate was found. The obtained products have been investigated
using X-ray fluorescence spectrometry and X-ray diffraction analysis. 相似文献