1,721,062 research outputs found
High-performance liquid chromatographic determination of Mn(II), Co(II), Zn(II), Ni(II), Cu(II) as coproporphyrin-I complexes
No full textThe mobilities of 3,8,13,18-tetrametyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) and five metal-CPI complexes were measured by reversed-phase high performance liquid chromatography (RP-HPLC) on a octadecyl-bonded silica gel (C18 silica) with developing solvent (69:31 v/v) methanol-buffer at pH 7 (buffer ionic strength 0.270 mol L−1. 0.018 mol L−1 boric, phosphoric and acetic acid, and 0.036 mol L−1 sodium hydroxide), and 0.050 mol L−1 of NaCl, with UV detection at 374 and 458 nm
Kinetic and equilibrium studies on mercury(II)-coproporphyrin-I. Metal ion exchange reaction with cobalt(II) and application to determination of trace mercury(II)
No full textThe reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) with mercury(II) was studied spectrophotometrically, and kinetic and equilibrium constants were determined; the influence of temperature on the reaction rate was also studied. It was verified that mercury(II) accelerates the incorporation reaction of cobalt(II) into CPI; the kinetics and mechanism of this reaction at high alkaline pH were studied. Sensitive kinetic methods for the determination of mercury(II) at ppb levels have been established; the apparent molar absorbivity and Sandell's sensitivity for the recommended procedure, at 368 nm, and 400 s after the start of the reaction, were: 4.23×105 (l mol−1cm−1) and 0.474 (ng cm−2) (for A=0.001)
Determination of stability constants of Cu(II), Co(II), Zn(II), Ni(II) and Mn(II) chelates with 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid by reversed-phase high performance liquid chromatography
No full textThe stability constants (KML) of Cu(II), Co(II), Zn(II), Ni(II), and Mn(II) chelates with 3, 8, 13, 18 -tetrametyl-21H, 23H-porphine -2,7,12,17- tetrapropionic acid, or coproporphyrin-I (CPI) have been determined by reversed-phase high performance liquid chromatography (RP-HPLC) on a octadecyl-bonded silica gel (C18 silica) with developing solvent (69:31 v/v) methanol-buffer at pH 7 (buffer ionic strength 0.270 mol L−1: 0.018 mol L−1 boric, phosphoric and acetic acid, and 0.036 mol L−1 sodium hydroxide), and 0.050 mol L−1 of NaCl, with UV detection.
The values of log KML were 6.02±0.26 for the Cu(II), 5.37±0.18 for the Co(II), 4.51± 0.21 for the Zn(II), 4.52± 0.21 for the Ni(II) and 6.38± 0.04 for the Mn(II)
Kinetic evidence for the effect of salts on the oxygen solubility using laboratory prototype aeration system
No full textThis study is dedicated to an accurate evaluation of thermodynamic and kinetic aspects in the oxygenation process of water/salt solutions. Oxygenation has been analyzed by means of kinetic study of oxygen dissolution from the oxygen mass transfer coefficient (KLa) and oxygen transfer rate (SOTR). A stirred, submerged aerated 4-liter system has been designed and the operational conditions have been optimized by studying the influence of hydraulic head, air flow and salinity of water using an optical oxygen sensor. Concerning the thermodynamic phase equilibria, experimental and modeling results are obtained from different binary systems (water/air) and ternary systems (water/air/salts). This information is necessary to predict the composition of the gas phase during the process and is also important for an implementation in a process simulation. The oxygen mass transfer coefficients were firstly measured, by monitoring in the time the oxygen concentration in various synthetic liquid phases containing different salts (NaCl, KCl, LiCl). When compared to clean water, noticeable increase of KLa was observed; the variation of KLa and SOTR with the solution salinity was modeled and found dependent on the nature of cation in the salt added. For all cases, an increase of KLa with increasing salinity was observed but, when the results are correlated with salt molar concentration, very important relation attributed to different salts has been obtained. The present study clearly confirmed the importance to define the experimental conditions before to describe and to model appropriately the gas-liquid mass transfer phenomena
The use of spectrophotometry UV-Vis for the study of porphyrins
Full text linkIn the porphyrins study, the evaluation of wavelength shift of adsorption bands and the absorbance changes as function of pH, temperature, solvent change, reaction with metal ions and other parameters permits to obtained accurate information about equilibrium, complexation, kinetic and aggregation. This chapter of the book, resumes the best successes in the use of UV-Vis spectrophotometry for explained the chemical characteristics of this extraordinary group of natural occurring molecules and clarifies the potential of these molecules in many fields of application
Reactions of metal-ions with 3,8,13,18-tetramethyl-21H, 23H-porphine-2,7,12,17-tetrapropionic acid: mechanisms, kinetics and analytical applications
No full textReactions of metal-ions with 3,8,13,18-tetramethyl-21H, 23H-porphine-2,7,12,17-tetrapropionic acid: mechanisms, kinetics and analytical application
Complessi del rame(II) e del cobalto(II) con coproporfirina-1 e loro caratterizzazione spettrofotometrica
No full textStudy of solvent extraction of mercury(II) with dibenzo-18-crown-6 from hydrochloric acid solution into benzene
No full textThe effect of Li+, K+, NH+4, Ca2+ or Sr2+ in the extraction of mercury(II) as chloro-complexes from solutions in hydrochloric acid with dibenzo-18-crown-6 (DB18C6) into benzene and the stoichiometries of the reactions have been studied. The crystalline extracted species were characterized by morphological and microanalysis measurements by scanning electron microscopy and energy dispersive X-ray spectrometry respectively
Sensitization of monolayer transparent TiO2 thin films with metal-porphyrin dyes for DSSC applications. Equilibrium and kinetic aspects.
Full text linkFor the best manufacture of dye-sensitized solar cell (DSSC) systems (Figure 1), optimum objectives are represented from very rapid and complete adsorption of single layer of dye on the semiconductor surface [1,2].
Cu(II) and Zn(II) complexes of Coproporphyrin-I or CPI (Figure 2), has been synthesized in our laboratory and tested as sensitizers in DSSC devices [3,4].
A systematic study of kinetic and equilibrium for the adsorption of metal-CPI-dyes onto TiO2 monolayer surfaces, have permit to establish the best experimental conditions for the adsorption of these dyes and have demonstrated that the metal-CPI-dyes, according to the Langmuir model and with pseudo first-order kinetics, are adsorbed effectively in the support of TiO2 monolayer without chemical changes. The suppression of the dyes aggregation have permitted the optimization of selective adsorption of one layer of dyes molecules to stoichiometric ratios improving performances in DSSC indicating therefore a powerful experimental strategy, that can be enlarged to other dyes
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