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1.
The electrochemical behavior and amperometric-FIA quantification of minoxidil at a glassy carbon electrode is described. The procedure is based on electrochemical oxidation at 0.800 V (vs. Ag/AgCl/NaCl(3 M) in a phosphate buffer solution. Minoxidil was determined over the range 1 x 10(-7) - 1 x 10(-4) M. Different analytical parameters and electrode stability were analyzed to obtain the best electrode performance. The optimal conditions were: working potentials, 0.800 V; flow rate, 0.74 mL min(-1); and solution pH 7.0. This system allowed a sampling rate of 120 samples per hour without any pretreatment. The proposed method was used for minoxidil quantification in pharmaceutical preparations with satisfactory results. The accuracy of FIA-amperometric method was established by a comparison with the conventional UV determination technique using a paired t-test indicating the absence of systematic errors. 相似文献
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A. I. Alonso A. M. Urtiaga S. Zamacona A. Irabien I. Ortiz 《Journal of membrane science》1997,130(1-2):193-203
In this work it is reported that the kinetic modelling of the separation of cadmium from phosphoric acid by non-dispersive solvent extraction. Using Cyanex 302 as selective extractant, the extraction step was carried out in a hollow fibre module containing polypropylene fibres, whereas the concentration step required a ceramic module with tubular channels due to the high acidity of the backextraction agent. Application of the methodology previously reported by the authors led to the development of a kinetic model with three design parameters, i.e., equilibrium constant of the extraction reaction (K'e = 6 × 103 mol−2/l−2), membrane mass transport coefficient of the extraction module Kme=8.33×10−8 m/s) and of the backextraction module (Kms=3.33×10−8 m/s), that described satisfactorily the behaviour of the separation-concentration system. Thus, in this work a new application of the non-dispersive solvent extraction technology is presented, characterising at the same time the behaviour and parameters of a new type of contactor, i.e., a tubular ceramic module. 相似文献
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Y. BallesterosM.J. Gonzalez de la Huebra M.C. QuintanaP. Hernandez L. Hernandez 《Microchemical Journal》2003,74(2):193-202
The electrochemical behaviour of kinetin (6-furfurylaminopurine) on a carbon paste modified with OV-17 silicone electrode, is studied. The determination of kinetin is possible working in square wave voltammetric techniques, reaching limits of determination of 38.7 ng ml−1. The proposed method was successfully applied to determine the cytokinin in extracts of apples (previously spiked with kinetin) and the obtained results were in accordance with the results obtained with HPLC-UV. 相似文献
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J. Hernandez Mendez A. Sanchez Perez F. Lucena Conde 《Journal of Electroanalytical Chemistry》1975,66(1):53-65
The anodic oxidation of a dropping copper amalgam electrode in presence of dilute solutions of glycine in 0.50 M NaClO4 has been studied. An anodic wave at ?0.28V (SCE) is observed, yielded by diffusion of glycinate anion in the solution towards the electrode surface. The wave-heights increase with the glycinate concentration (function of glycine concentration and pH value) until the anodic oxidation is controlled by the metal diffusion into mercury. The effect of pH is interpreted by attributing it to the depolarizer effects at glycinate anion even though the zwitterion is present in much larger concentrations. The applicability of anodic oxidation of a dropping copper amalgam electrode in the determination of glycine in the range of concentrations 10?4–10?2M with a rigorous control of pH (8.0<pH<10.5) is shown. The standard deviation of the proposed method is 4.1% and the minimum concentration determinable is in the 1×10?4M range. 相似文献
8.
N. G. Naumov K. A. Brylev S. Cordier O. Hernandez C. Perrin V. E. Fedorov 《Journal of Structural Chemistry》2003,44(4):698-703
Two new compounds containing molybdenum thiocyanide cluster anions, K6[Mo4S4(CN)12]·10H2O (1) and (18-crown-6K)8[Mo6S6(CN)16]·17.5H2O (2), were synthesized and investigated by X-ray structure analysis. Crystal data: a=11.8430(17), b=11.8430(17), c=35.170(7) , V=4932.8(14) 3, space group I41/a, Z=4, dcalc=1.563 g/cm3 for 1; a=28.7513(5), b=18.4190(3), c=20.7586(4) , =118.5982(7)°, V=9651.9(3) 3, space group C2/m, Z=4, dcalc =1.563 g/cm3 for 2. The [Mo4S4(CN)12]6- cluster anion in 1 has an ordinary structure typical of cubane transition metal complexes. In the structure of the [Mo6S6(CN)16]8- anion of 2, two crystallographically independent molybdenum atoms form a Mo6 metallocluster, represented as two edge-sharing tetrahedra. 相似文献
9.
Ortiz ME 《Physical review D: Particles and fields》1992,45(8):R2586-R2589
10.
A rapid and simple fractionation procedure using solid-phase extraction (SPE) cartridges was developed for an accurate determination of aliphatic and polycyclic aromatic hydrocarbons in petroleum residues and further application in chemical fingerprinting of oil spills by gas chromatography-mass spectrometry (GC-MS). Among the adsorbents evaluated, SiO2/C3-CN exhibited the best selectivity, providing, by elution with n-hexane (4 ml) and n-hexane-CH2Cl2 (1:1) (5 ml), two well-resolved aliphatic and aromatic hydrocarbon fractions, with recoveries of 97 +/- 7.2 and 99.7 +/- 13.9%, respectively. The SPE fractionation procedure was compared with the conventional silica-alumina adsorption chromatography showing similar results but practical advantages in terms of reproducibility, analysis time, solvent reduction and cost. Moreover, is particularly suitable for routine analysis with a high sample throughput. The developed methodology was tested in the characterization of fuel-oil samples collected along the Spanish north-west coast, after the Prestige oil spill accident. 相似文献