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A rapid and reliable capillary zone electrophoresis method for the determination of inorganic cations was developed. The complete separation of K+, Ba2+, Ca2+, Na+, Mg2+, Mn2+, Ni2+, Cd2+, Li+ and Cu2+ can be achieved in 4 min with a simple electrolyte composed by 10 mM imidazole as the carrier buffer and background absorbance provider and acetic acid as the complexing agent (pH 3.60). Injection was performed hydrostatically by elevating the sample at 10 cm for 30 s. The running voltage was +25 kV at room temperature. Indirect UV-absorption detection was achieved at 185 nm. The detection limit was in the range between 0.06 mg/l (Mg2+) and 0.57 mg/l (K+) and the quantification limits ranged from 0.10 mg/l (Ni2+) to 0.80 mg/l (Cu2+). The calibration graphs were linear in the concentration range from the quantification limit till at least 1 g/l in K+, 10 mg/l in Ba2+, Ca2+, Mg2+, Mn2+, Ni2+ and Cd2+, 40 mg/l in Na+ and 12 mg/l in Li+ and Cu2+. The repeatability, intraday and interday analysis were ≤1.55% and ≤3.64% for migration time and ≤3.38% and ≤3.63% for peak area. The method developed has been applied to several beverage samples with only a simple dilution and filtration treatment of the sample. The proposed method is simple, fast, cheap and it is achieved with common products in either laboratory. For these reasons, it is a very useful method for routine analysis. 相似文献
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C. Vazquez N. Lago M. M. Mato L. M. Casas L. Esarte J. L. Legido I. Arias 《Journal of Thermal Analysis and Calorimetry》2014,116(1):107-112
Microcalorimetry is a technique that determines the heat flow produced as a result of microbial activities. The heat variations resulting from chemical reactions, which take place during metabolism, can be used to monitor bacterial growth in a culture medium. However, there are very few studies using calorimetry to investigate the relationships between two bacteria. In this work, we studied the interaction between E. coli and P. mirabilis, two bacteria belonging to the family Enterobacteriaceae. We have prepared three samples, mixing both enterobacteria at a concentration of 103 CFU mL?1 but in different proportions. Experimental equipment used was a Calvet microcalorimeter, where a constant temperature of 309.65 K was maintained. Then, we compared the shape of the heat flow–time curves of single microorganisms and their mixtures. Also, we calculated the thermokinetic parameters such as growth constant (k), generation time (G), detection time (t d) and the amount of heat released (Q). The results obtained showed that when E. coli and P. mirabilis were put together in the culture medium, the growth profile of P. mirabilis seemed to dominate, even at low proportions in the sample. 相似文献
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George A Knez M Hlawacek G Hagedoorn D Verputten HH van Gastel R ten Elshof JE 《Langmuir : the ACS journal of surfaces and colloids》2012,28(5):3045-3052
A simple methodology to fabricate micrometer- and nanometer-scale patterned surfaces with multiple chemical functionalities is presented. Patterns with lateral dimensions down to 110 nm were made. The fabrication process involves multistep gas-phase patterning of amine, thiol, alkyl, and fluorinated alkyl-functional organosilane molecules using PDMS molds as shadow masks. Also, a combination process of channel diffused plasma etching of organosilane molecular thin films in combination with masked gas-phase deposition to fabricate multilength scale, multifunctional surfaces is demonstrated. 相似文献
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Isothermal vapor-liquid equilibrium (VLE) data, at 25° C were determined by a saturation method for each of the six methanol or methyl acetate binary systems with dichloromethane, chloroform, and 1,2-trans-dichloroethylene. The experimental data satisfy the Redlich-Kister consistency test, and were correlated with five Gibbs free energy models. All the binary mixtures of methanol with the chlorinated compounds exhibit strong positive deviations from ideality while the mixtures of methyl acetate with the chlorinated compounds present negative deviations from ideal behavior.Communicated at the Festsymposium celebrating Dr. Henry V. Kehiaian's 60th birthday, Clermont-Ferrand, France, 17–18 May 1990. 相似文献
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Rapid determination of minority organic acids in honey by high-performance liquid chromatography 总被引:8,自引:0,他引:8
Suárez-Luque S Mato I Huidobro JF Simal-Lozano J Sancho MT 《Journal of chromatography. A》2002,955(2):207-214
A rapid high-performance liquid chromatographic method for the determination of organic acids in honey is reported. Malic, maleic, citric, succinic and fumaric acids were identified and quantified in 15 min. First time repeatibility, reproducibility and recoveries were determined out for these acids in honey samples. Maleic acid was also quantified for first time by a chromatographic method. The organic acids were removed from honey by using a solid-phase extraction procedure with anion-exchange cartridges. Previously, the solution of honey was adjusted to pH 10.50 with 0.1 M NaOH and stirred for 15 min at room temperature. Then, this solution was adjusted to pH 5.00 with 0.1 M H2SO4. This procedure was carried out to avoid interferences in the baseline. The chromatographic separation was achieved with only one Spherisorb ODS-2 S5 column thermostated at 25 degrees C. Metaphosphoric acid (pH 2.20) was used as mobile phase at a flow-rate of 0.7 ml/min. Organic acids were detected with a UV-vis detector (215 nm). The precision results showed that the relative standard deviations of the repeatability and reproducibility were < or =3.20% and < or =4.86%, respectively. The recoveries of the organic acids ranged from 62.9 to 99.4%. Under optimum conditions the detection limits ranged from 0.0064 to 7.57 mg/kg and the quantification limits ranged from 0.025 to 10.93 mg/kg. 相似文献
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M. M. Mato S. M. Cebreiro P. V. Verdes J. L. Legido M. I. Paz Andrade 《Journal of Thermal Analysis and Calorimetry》2005,80(2):303-309
Experimental excess molar enthalpies and excess molar volumes of the ternary system x1MTBE+x21-propanol+(1-x1-x2) hexane and the involved binary mixtures have been determined at 298.15 K and atmospheric pressure. Excess molar enthalpies were measured using a standard Calvet microcalorimeter, and excess molar volumes were determined from the densities of the pure liquids and mixtures, using a DMA 4500 Anton Paar densimeter. The UNIFAC group contribution model (in the versions of Larsen et al., and Gmehling et al.) has been employed to estimate excess enthalpies values. Several empirical expressions for estimating ternary properties from experimental binary results were applied. 相似文献
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M. M. Mato P. V. Verdes M. Illobre J. L. Legido M. I. Paz Andrade 《Journal of Thermal Analysis and Calorimetry》2008,92(1):185-189
Excess molar enthalpies, measured at 298.15 K in a Calvet microcalorimeter, are reported for {x 1 tert-butyl methyl ether (MTBE)+x 2ethanol (EtOH)+(1?x 1?x 2)heptane}. Smooth representations of the results are presented and used to construct contant excess molar enthalpy contours on Roozeboom diagrams. 相似文献