USE OF HIGH SURFACE NANOFIBROUS MATERIALS IN MEDICINE

n/

Preconcentration of manganese(II) from natural and sea water on a palmitoyl quinolin-8-ol functionalized XAD copolymer resin and spectrophotometric determination with the formaldoxime reagent

A palmitoyl quinolin-8-ol (P.Ox)-functionalized Amberlite XAD-2 copolymer resin (XAD-P.Ox) was used in the column mode to preconcentrate trace Mn(II) from artificial and real seawater, and Mn in the eluate was determined by the formaldoxime (FAD) spectrophotometric method, the results compared with those of FAAS. The optimal pH interval of Mn uptake by the resin was between pH 7 and 10 (best at 8). Other column operation parameters such as adsorption and elution flow rate, and eluent volume were optimized. Since a preconcentration factor of approximately 60 was achieved with the resin column, the detection limits (LOD) of spectrophotometry and FAAS for Mn (i.e. 17 and 12 mug l(-1), respectively) were significantly reduced. The most serious interferent to the FAD procedure, i.e. ferric iron, was eliminated using the resin retention-elution procedure. The proposed method of preconcentration and analysis of Mn(H) was not adversely affected from high ionic strength media, rendering the method suitable for Mn determination in seawater. (C) 2003 Elsevier Science B.V. All rights reserved

Speciation analysis of chromium by separation on a 5-palmitoyl oxine-functionalized XAD-2 resin and spectrophotometric determination with diphenylcarbazide

The method developed in this work for the separation and preconcentration of Cr(III) is based on its retention by an Amberlite XAD-2 copolymer resin functionalized with 5-palmitoyl-8-hydroxyquinoline (oxine), abbreviated XAD-POx, with the ligand covalently bound to the copolymer. Cr(III) sorption was quantitative within the pH range 4.5-7.0 and Cr(VI) was not retained. The Cr(III) held by the resin column was eluted with a hot solution of H2O2 in pHgreater than or equal to9.0 aqueous NH3-NH4Cl buffer, and Cr oxidized to CrO42- was rejected by the chelating cation-exchanger column. Any Cr(VI) originally present with Cr(III) could be reduced with an acidic solution of H2O2, and retained by the column yielding total Cr results, Cr(VI) being determined from the difference. The resin showed a maximal preconcentration factor of 60 for Cr(III), the LOD and LOQ being 9.3 and 30.1 nmol L-1, respectively. The developed preconcentration-speciation analysis was finished with a diphenylcarbazide (DPC) spectrophotometric procedure suitable for conventional laboratories. The resin showed excellent salt tolerance, enabling Cr analysis in seawater, and was stable over extended use. All the interferents of this procedure that normally occur in an electroplating effluent, a blended coal CRM, and a standard steel sample could be removed by the recommended procedure, by use of partial and total selectivity at the adsorption and desorption stages, respectively, enabling preconcentration and colorimetric determination of chromium in various complex matrices

Preconcentration and speciation of chromium using a melamine based polymeric sequestering succinic acid resin: its application for Cr(VI) and Cr(III) determination in wastewater

A new melamine based polymeric sequestering resin was prepared for preconcentration and separation of hexavalent chromium from water, and its sequestering action was investigated. The water-insoluble, cross-linked sequestering resin was formed by reaction with bromosuccinic acid and cross-linking of melamine. The active sequestering group on the resin is -NH-(Succinic acid) or salt thereof. The resulting chelating resin was characterized by infrared spectra. The newly prepared resin quantitatively retained Cr(VI) at pH 2.0-4.0 when the flow rate was maintained between 1 and 5 ml min(-1). The retained Cr(VI) was instantaneously eluted with 25 ml of 0.1 M NaOH. The chromium species were determined by a flame atomic absorption spectrometer. The limits of detection for Cr(VI) and Cr(III) were found to be 5.3 and 4.2 mug 1(-1), respectively. The precision and accuracy of the proposed procedure was checked by the use synthetic and reference steel samples. The established preconcentration method was successfully applied to the determination and selective separation of Cr(VI) in electroplating industry wastewater. Total concentrations determined by the spectrophotometric method (110.3+/-0.6 g 1(-1) Cr(VI) and 1.2+/-0.3 g 1(-1) Cr(III)) are compared with those found by FAAS and the obtained results (110.4+/-1.8 g 1(-1) Cr(VI) and 1.4+/-0.5 g 1(-1) Cr(III)) show good agreement. (C) 2003 Published by Elsevier Science B.V

The use of palmitoyl hydroxyquinoline-functionalized amberlite XAD-2 copolymer resin for the preconcentration and speciation analysis of gallium(III)

Gallium (Ga) is a valuable element in the electronics industry for manufacturing semiconductors and lasers. The processing of bauxite ores for the recovery of Ga, as well as high-level purification of the raw Ga product as required by electronic applications, necessitate effective speciation analysis of this element. For differentiating chemically important Ga(III) species, the Amberlite XAD-2 polystyrene-divinylbenzene copolymer was chloromethylated using AlCl3 as a catalyst, and later, 5-palmitoyl-8-hydroxyquinoline was covalently bound to this chloromethylated product via Friedel-Crafts reaction, resulting in the synthesis of a Ga-specific resin (Amberlite XAD-2-P.Ox)

Separation and preconcentration of iron(II) and iron(III) from natural water on a melamine-formaldehyde resin

A combined method for the preconcentration and selective spectrophotometric determination of both valencies of iron, i.e., Fe(II) and Fe(III), down to 0.4 mu g l(-1) has been developed. Iron(III) from synthetic and natural water samples has been concentrated on a melamine-formaldehyde resin at pH 5; iron(II) was not retained under identical conditions. The oxidized iron was concentrated on a second resin column. The iron in both columns was eluted with 1 M HCl solution and separately analyzed by the 1,10-phenanthroline-citrate spectrophotometric method. The effect of pH, adsorption and elution rates, and interferences on the developed procedure were investigated. Metal ions that can be retained by the resin at moderate concentrations, e.g., Al3+, do not cause interference in more dilute solutions encountered in natural water samples. At least 160-fold volume enrichment can be easily obtained using an adsorption flowrate of 50 ml min(-1). A hydrothermal water sample was analyzed by the recommended procedure and by a literature method, and the results were statistically compared by t- and F-tests. (C) 1997 Elsevier Science B.V

Concerted heavy-atom bond cleavage and proton and electron transfers illustrated by proton-assisted reductive cleavage of an O–O bond

Electron transfer may be concerted with proton transfer. It may also be concerted with the cleavage of a bond between heavy atoms. All three events may also be concerted. A model is presented to analyze the kinetics of these all-concerted reactions for homogeneous or electrochemical reduction or oxidation processes. It allows the estimation of the kinetic advantage that derives from the increase of the bond-breaking driving force resulting from the concerted proton transfer. Application of the model to the electrochemical reductive cleavage of the O–O bond of an organic peroxide in the presence of a proximal acid group illustrates the applicability of the model and provides an example demonstrating that electron transfer, heavy-atom bond breaking, and proton transfer may be all concerted. Such analyses are expected to be useful for the invention, analysis, and optimization of reactions involved in contemporary energy challenges as well as for the comprehension of major biochemical processes, a number of which involve electron and proton transfer together with cleavage of bonds between heavy atoms