1,721,051 research outputs found
"Polarographic and voltammetric studies of tetrabutyl- ammoniumnium hexacyanoferrate(III) and tetrabutylammonium hexacyanomanganate(III) in non-aqueous solvents"
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CEC enantioseparations on chiral monolithic columns: A study of the stereoselective degradation of (R/S)-dichlorprop [2-(2,4-dichlorophenoxy)propionic acid] in soil
No full textFor the study of the stereoselective degradation of the herbicide 2-aryloxipropionic acid dichlorprop (DCPP) in soil, a porous monolithic chiral column (100 μm id) was prepared by in situ copolymerization of glycidyl methacrylate, methyl methacrylate and ethylene glycol dimethacrylate in the presence of formamide and 1-propanol as the porogen solvents. Subsequently, the epoxide groups at the surface of the monolith were reacted with (+)-1-(4-aminobutyl)-(5R,8S,10R)-terguride as the chiral selector. Optimum conditions for the herbicide resolution by CEC were found using mobile phases consisting of acetic acid/ triethylamine mixtures in ACN-methanol (9:1 v/v). Under these conditions fully separation of DCPP enantiomers in the presence of clofibric acid (internal standard) was achieved in about 5 min. Experiments on the incubation of rac-DCPP in soil at room temperature showed the herbicide undergone during 23 incubation days to a degradation to levels ≤20% of the initial concentration, with rates for (R)-DCPP slower than (S)-DCPP. More interesting results were observed when herbicide enantiomers were individually incubated. In both the experiments, the formation of the opposite isomer in the presence of the initial one, and reversed enantiomeric interconversion in the case of (S)-DCPP was observed. (R)-DCPP was found to be the most persistent isomer after incubation. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Phenols removal by immobilized tyrosinase reactor in on-line high performance liquid chromatography
No full textThe development of an immobilized enzyme reactor (IMER) based on tyrosinase immobilized on aminopropyl-controlled pore glass (AP-CPG) for the removal of phenols from model aqueous solutions was reported. To elucidate the influence of the substrate nature, the apparent (V'(max), K'(m)) and the inherent (V-max, K-m) Michaelis-Menten constants were determined by Lineweaver-Burk method and the external diffusional contributions on measured enzyme activities were removed by a graphical method. The dephenolization process was realized by recycling the phenol solutions through the bioreactor connected to a chitosan trap in order to remove the colored quinone-type products of the tyrosinase reactions. The results indicated that a complete removal of phenol derivatives in the range of 150-300 min, with the exception of 60% removal for phenol reached in 400 min, was obtained. The observed sequence: cresol > 4-methylcathecol > catechol > 4-Cl-phenol >> phenol was in accordance to the V'(max)/K'(m) values. (c) 2006 Elsevier B.V. All rights reserved
"Structure and reactivity in octahedral complexes XIV Acid-catalyzed aquations of cis- and trans-dicarboxylato-bis(ethylenediamine)cobalt(III) complexes"
No full text"Liquid chromatographic resolution of enantiomers on chiral amine derivative-bonded silica gel"
No full text"Thin layer chromatographic and "in situ" spectrophotometric determination of products in solid-solid thermal reaction"
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