The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Antonio Molinadiaz - One of the best experts on this subject based on the ideXlab platform.
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indirect spectrophotometric determination of ascorbic acid with Ferrozine by flow injection analysis
Talanta, 1998Co-Authors: Antonio Molinadiaz, I Ortegacarmona, M I PascualregueraAbstract:Abstract A FIA indirect spectrophotometric determination of ascorbic acid was developed using its reducing action on Fe(III) in acidic medium and following the spectrophotometric determination of the reduced iron by using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4′,4″-disulphonate (Ferrozine) as chromogenic reagent in buffered medium (pH 5.5) and monitoring the absorbance signal at 562 nm. A three-line manifold with two reaction coils was used: in the first reaction coil, ascorbic acid reduces Fe(III) to Fe(II); and in the second one, the complexation reaction is developed. The linear range of the method was 0.5–10 μg ml−1 of ascorbic acid, the detection limit being 0.028 μg ml−1. The proposed method was sensitive, rapid (sampling rate of 90 samples h−1) and reproducible (RSD 0.19%, n=10). Satisfactory results were obtained in the determination of ascorbic acid in pharmaceutical preparations, fruit juices and urine testifying the applicability of the method to real samples.
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spectrophotometric determination of iron with Ferrozine by flow injection analysis
Talanta, 1997Co-Authors: M I Pascualreguera, I Ortegacarmona, Antonio MolinadiazAbstract:Abstract Two methods for the determination of iron by normal FIA and reversed FIA were developed using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4′,4″-disulphonate (Ferrozine). The reagent formed a chelate with Fe(II) in hexamethylentetramine buffered medium at pH 5.5. In one previous reaction coil Fe(III) was reduced to Fe(II) by ascorbic acid and in the other reaction coil the complexation reaction was developed. The linear range of the determination was 0.5–6 and 0.1–5 μg ml −1 of iron for normal FIA and reversed FIA respectively. The proposed method was sensitive (detection limit 0.012 and 0.010 μg ml −1 ), rapid and reproducible (RSD 0.3 and 0.28%). The method was satisfactorily applied to the determination of iron in waste water, toadstool tissue, potato leaves, human hair and bauxites at a sampling rate of 90 and 50 samples h −1 for normal FIA and reversed FIA respectively.
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solid phase spectrophotometric microdetermination of iron with ascorbic acid and Ferrozine
Fresenius Journal of Analytical Chemistry, 1997Co-Authors: M Fernandezde L Cordova, A Ruizmedina, Antonio MolinadiazAbstract:A very sensitive and selective method for the determination of trace amounts of iron has been developed, based on the reduction of Fe(III) to Fe(II) by ascorbic acid, followed by chromogenic chelation of Fe(II) with Ferrozine. The complex Fe(II)-Ferrozine is easily sorbed on a dextran-type anion-exchange gel packed in a 1 mm cell, and the absorbance of the gel is measured directly at 569 and 800 nm. The extended linear range of the determination is 0.5–10 ng ml-1 of iron (apparent molar absorptivity=4.4×107 l mol-1 cm-1) and the precision (RSD) 1.3% for a concentration of 5 ng ml-1 of iron (n=10). The detection limit for a sample volume of 1000 ml, using 0.040 g of anion-exchanger, corresponds to 0.12 ng ml-1. The method has been successfully applied to the determination of iron in natural and waste waters, wine, soil extract and previously digested vegetal tissues, drugs and human hair.
M I Pascualreguera - One of the best experts on this subject based on the ideXlab platform.
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indirect spectrophotometric determination of ascorbic acid with Ferrozine by flow injection analysis
Talanta, 1998Co-Authors: Antonio Molinadiaz, I Ortegacarmona, M I PascualregueraAbstract:Abstract A FIA indirect spectrophotometric determination of ascorbic acid was developed using its reducing action on Fe(III) in acidic medium and following the spectrophotometric determination of the reduced iron by using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4′,4″-disulphonate (Ferrozine) as chromogenic reagent in buffered medium (pH 5.5) and monitoring the absorbance signal at 562 nm. A three-line manifold with two reaction coils was used: in the first reaction coil, ascorbic acid reduces Fe(III) to Fe(II); and in the second one, the complexation reaction is developed. The linear range of the method was 0.5–10 μg ml−1 of ascorbic acid, the detection limit being 0.028 μg ml−1. The proposed method was sensitive, rapid (sampling rate of 90 samples h−1) and reproducible (RSD 0.19%, n=10). Satisfactory results were obtained in the determination of ascorbic acid in pharmaceutical preparations, fruit juices and urine testifying the applicability of the method to real samples.
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spectrophotometric determination of iron with Ferrozine by flow injection analysis
Talanta, 1997Co-Authors: M I Pascualreguera, I Ortegacarmona, Antonio MolinadiazAbstract:Abstract Two methods for the determination of iron by normal FIA and reversed FIA were developed using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4′,4″-disulphonate (Ferrozine). The reagent formed a chelate with Fe(II) in hexamethylentetramine buffered medium at pH 5.5. In one previous reaction coil Fe(III) was reduced to Fe(II) by ascorbic acid and in the other reaction coil the complexation reaction was developed. The linear range of the determination was 0.5–6 and 0.1–5 μg ml −1 of iron for normal FIA and reversed FIA respectively. The proposed method was sensitive (detection limit 0.012 and 0.010 μg ml −1 ), rapid and reproducible (RSD 0.3 and 0.28%). The method was satisfactorily applied to the determination of iron in waste water, toadstool tissue, potato leaves, human hair and bauxites at a sampling rate of 90 and 50 samples h −1 for normal FIA and reversed FIA respectively.
Boon P Chock - One of the best experts on this subject based on the ideXlab platform.
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application of the continuous variation method to cooperative interactions mechanism of fe ii Ferrozine chelation and conditions leading to anomalous binding ratios
Biophysical Chemistry, 2002Co-Authors: Charles Y Huang, Rixin Zhou, David C H Yang, Boon P ChockAbstract:Abstract The method of continuous variation, often known as the Job plot, has long been used for determining the stoichiometry of two interacting components. The correct binding ratio, n, is generally obtained when the total concentration of the reactants, Co, is much greater than the dissociation constants involved. For non-cooperative binding systems, the stoichiometry varies between one and n as Co increases; whereas for positive cooperative systems, values larger than n may be observed at low Co. In this report, we present examples to illustrate how the changing apparent stoichiometries as a function of Co can provide clues for differentiating various binding mechanisms. To test these concepts, we examined the chelation of Fe(II) with Ferrozine in the range of Co=7 to 210 μM with Fe(II) expressed in molar concentration or in terms of its binding equivalents (three in this case). The results were analyzed according to several models and found to be most consistent with the mechanism of one-step complex formation or infinite cooperativity with a Kd of 8 μM.
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antioxidant activity of Ferrozine iron amino acid complexes
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Barbara S Berlett, Mordechai Chevion, Rodney L Levine, Boon P Chock, Earl R. StadtmanAbstract:Abstract Amino acid–Fe(II)–chelator complexes exhibit strong antioxidant activity. Taking advantage of the unique spectral characteristics of the complexes formed when Ferrozine (Fz) is used as the chelator, we now show that the primary blue complex (ɛmax at 632 nm) decomposes by two independent pathways: (i) a nonoxidative pathway involving dissociation of the amino acid component and formation of a purple complex (ɛmax at 562 nm) and (ii) an oxidative pathway leading to Fe(III) and colorless products. Quantitative conversion of the blue to purple complex yields an isosbestic point (i.p.) at 601 nm, whereas no i.p. is formed during quantitative oxidation of the blue complex. However, under some experimental conditions, decomposition of the blue product occurs by both pathways, leading to occurrence of a clean i.p. at wavelengths varying from 601 to 574 nm. Results of simulation experiments, confirmed by direct analysis, demonstrate that shifts in the i.p. reflect differences in the fractions of blue compound that decompose by the oxidative and nonoxidative pathways. Indeed, the fraction of blue that is converted to the purple complex is readily deduced from the wavelength of the i.p. These results suggest that identification of a physiological chelator that can replace Ferrozine in amino acid–iron complexes might have important physiological and pharmacological applications.
Masami Fukushima - One of the best experts on this subject based on the ideXlab platform.
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Determination of Labile Fe(II) Species Complexed with Seawater Extractable Organic Matter in a Seawater Environment
Functions of Natural Organic Matter in Changing Environment, 2012Co-Authors: Hisanori Iwai, Masami Fukushima, Mitsuo YamamotoAbstract:A fertilizer composed of a mixture of steel slag and compost was used to restore seaweed beds in barren coastal areas. Complex species of Fe(II) from steel slag are supplying Fe(II) to coastal areas and stimulating seaweed growth. Seawater extractable organic matter (SWEOM) from a compost can serve as a chelator of Fe(II) in the fertilizer. Among the Fe (II)-SWEOM complexes, readily indissociable and undissociable complex species are defined as “labile” and “inert,” respectively. The bioavailability of Fe(II)-SWEOM complexes is higher in the labile species. In the present study, a novel method for analyzing labile species of Fe(II)-SWEOM complexes under conditions of seawater (pH 8.0, I = 0.7) was developed. The method is based on a ligand-exchange reaction between SWEOM and Ferrozine, in which the Ferrozine-exchangeable Fe(II) in the Fe(II)-SWEOM complex corresponds to the labile Fe(II) species. Fe(II) is readily oxidized to Fe(III) in seawater. Thus, to avoid the oxidation of ferrous ions, ascorbic acid was added as an antioxidant, a situation that had no effect on the ligand-exchange reaction between SWEOM and Ferrozine. A comparison of the kinetic curve for the formation of the Fe(II)-Ferrozine complex in the absence and presence of SWEOM permitted the free [Fe(II)] and labile [Fe(II)-SWEOM] to be determined. In a variety of total Fe(II) concentrations, conditional binding constants for labile Fe(II)-SWEOM complexes and binding capacities of labile sites in SWEOM to Fe (II) were evaluated.
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evaluation of the binding of iron ii to humic substances derived from a compost sample by a colorimetric method using Ferrozine
Bioresource Technology, 2010Co-Authors: Mitsuo Yamamoto, Atsushi Nishida, Keishi Otsuka, Takeshi Komai, Masami FukushimaAbstract:Abstract In evaluating the quality of composts that include humic substances (HSs), the binding of iron(II) (conditional binding constants and binding capacities) are an important criteria. To determine the binding ability, it is necessary to determine the concentrations of free Fe2+ and Fe(II)–HS complex species present. In the present study, we describe a colorimetric method for determining free Fe2+ species using Ferrozine in an aqueous solution of Fe2+ and HS. It was found that the colored species in the Fe2+ and HS mixture represented only free Fe2+ species. Two water soluble fractions of HS, humic (HA) and fulvic (FA) acids, were isolated from a compost sample, and the conditional binding constants and binding capacities were estimated by colorimetric titration. Differences in the binding of Fe(II) to HA and FA are discussed, based on their structural features, which were characterized by acidic functional group analysis, elemental analysis and solid-state CP-MAS 13C NMR spectral data.
W I Stephen - One of the best experts on this subject based on the ideXlab platform.
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evaluation of some as triazines and re evaluation of pdt and Ferrozine as reagents for spectrophotometric determination of ruthenium
Talanta, 1992Co-Authors: M A Islam, W I StephenAbstract:Abstract A sensitive method for the spectrophotometric determination of ruthenium with the ferroinyielding as-triazines has been developed. This method has several advantages; complete reduction of ruthenium species to ruthenium(II) can be achieved by the recommended procedure, which shortens the colour development time, saves the unnecessary use of several-fold excess of the reagent and the molar absorptivity is increased significantly. A few of the new as-triazines together with the commercially available Ferene® have been evaluated as ruthenium(II) chromogens. 3-(2-Pyridyl)-5,6-diphenyl-as-triazine (PDT) and Ferrozine, a sulphonated derivative of PDT, have been re-evaluated by the new method. It has been observed that the as-triazine acting as a bidentate ligand forms a tris-complex with ruthenium(II) similar to its reaction with iron(II).