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111.
Antonio Calvo-López Eva Arasa-Puig Mar Puyol Joan Manel Casalta Julián Alonso-Chamarro 《Analytica chimica acta》2013
The construction and evaluation of a Low Temperature Co-fired Ceramics (LTCC)-based continuous flow potentiometric microanalyzer prototype to simultaneously monitor the presence of two ions (potassium and nitrate) in samples from the water recycling process for future manned space missions is presented. The microsystem integrates microfluidics and the detection system in a single substrate and it is smaller than a credit card. The detection system is based on two ion-selective electrodes (ISEs), which are built using all-solid state nitrate and potassium polymeric membranes, and a screen-printed Ag/AgCl reference electrode. The obtained analytical features after the optimization of the microfluidic design and hydrodynamics are a linear range from 10 to 1000 mg L−1 and from 1.9 to 155 mg L−1 and a detection limit of 9.56 mg L−1 and 0.81 mg L−1 for nitrate and potassium ions respectively. 相似文献
112.
HPLC method enabling chiral separation and determination of citalopram (CIT), a widely used antidepressant, and its synthetic precursor citadiol in one analysis was developed and validated. Moreover, supercritical fluid chromatography was also tested and was proved to be less effective for this separation purpose. The optimized HPLC system was composed of Chiralcel OD-H column and n-hexane/propane-2-ol/triethylamine 96/4/0.1 (v/v/v) as mobile phase, column temperature 25 °C, flow rate 1.0 mL min?1, UV detection at 250 nm. The effects of amount of propane-2-ol, triethylamine addition, and temperature on enantioselectivity and resolution of the enantiomers were evaluated. The method was found to be suitable for determination of the enantiomeric purity of CIT in bulk drugs. Enantiomers of CIT were determined in two commercially available pharmaceuticals. 相似文献
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Surfaces coated with poly(ethylene oxide) containing nonionic polymers are of interest in medical applications due to, among other things, the low adsorption of proteins on such surfaces. In this paper we have studied the interfacial properties of surfaces coated with PEO by measuring the forces acting between two such surfaces in water and across a protein solution as well as between one such surface and a surface carrying adsorbed proteins. One type of surface coating was a graft copolymer of poly(ethylene imine) and poly(ethylene oxide) where the cationic poly(ethylene imine) group anchored the polymer to negatively charged mica surfaces. Three different ways to prepare this coating was used and compared. It was found that this coating was not stable in the presence of lysozyme, a small positively charged protein, when the PEO graft density was low. The other type of coating was obtained by adsorbing ethyl(hydroxyethyl)-cellulose onto hydrophobised mica surfaces. The driving force for adsorption is in this case the hydrophobic interaction between nonpolar segments of the polymer and the surface. The EHEC coating was stable in the presence of lysozyme and the interactions between adsorbed layers of lysozyme and EHEC coated surfaces are purely repulsive due to long-range steric forces. 相似文献
116.
Eva Hoffmann GyÖrgy Marko-Varga Istvan Csiky Jan Årke JÖnsoon 《International journal of environmental analytical chemistry》2013,93(1-3):161-171
Abstract A three-column ion chromatographic system for the removal of humic substances from natural waters, and subsequent on-line concentration and determination of nitrate and sulfate using non-suppressed ion chromatography is presented. Humic substances are removed using disposable adsorption columns packed with chemically bonded amine silica material. The sample is directly transfered to an ion exchange column where the anions are concentrated ca 10 times. After reversing the flow, the ions are transferred to a third column where they are separated and quantified. The detection limit is less than 1 mg L?1 of nitrate or sulfate in water containing 45mgL?1 of humic acid. 相似文献
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Alfonsina E. Andreatta Eva Rodil Alberto Arce Ana Soto 《Journal of solution chemistry》2014,43(2):404-420
New experimental surface tension data have been provided at 283.15, 298.15, 313.15 K and atmospheric pressure for binary mixtures of 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide and 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with the alcohols: methanol, ethanol, 1-propanol, 2-propanol, l-butanol and 1-pentanol. The experimental results show that the surface tensions of these mixtures depend systematically on the alkyl chain length of the ionic liquid and alcohol, composition and temperature. Surface tension changes on mixing have been calculated and adequately fitted by the Redlich–Kister polynomial equation. The adjustable parameters and the standard deviations between experimental and calculated values are reported. 相似文献
120.
Miha Drev Uroš Grošelj Špela Mevec Eva Pušavec Janja Štrekelj Amalija Golobič Georg Dahmann Branko Stanovnik Jurij Svete 《Tetrahedron》2014
The synthesis of 7-substituted pyrazolo[1,5-a]pyrimidine-3-carboxamides was studied. First, methyl 7-hydroxypyrazolo[1,5-a]pyrimidine-3-carboxylate (5) was prepared in three steps from methyl 5-amino-1H-pyrazole-4-carboxylate (3). Treatment of 5 with POCl3 gave the highly reactive 7-chloro derivative 10, which was reacted with amines, benzyl alcohol, and phenylboronic acid in the presence of Pd-catalyst to give the corresponding 7-substituted derivatives 11. Hydrolysis of the esters 5 and 11 followed by amidation gave the corresponding carboxamides 16a–h and 15. Regioselectivity of N-alkylation of 7-hydroxypyrazolo[1,5-a]pyrimidine-3-carboxylic acid derivatives 5 and 16 was tunable by the carboxy function. Alkylation of the secondary amides 16a–f furnished the 1-alkyl derivatives 17a–f, whereas the ester 5 and the tertiary amides 16g,h gave the 4-alkyl derivatives 14a–d and 16m,n, selectively. 相似文献