Sequential determination of trace amounts of iron and copper in water samples by flow injection analysis with catalytic spectrophotometric detection.

A simple flow injection analysis (FIA) method is described for the sequential determination of iron and copper. The detection method for iron and copper is based on their catalytic activities in the oxidation reaction of N,N-dimethyl-p-phenylenediamine (DPD) with hydrogen peroxide. The sequential determination of iron and copper can be carried out by injecting two sample plugs into the FIA system, sequentially. One injection does not contain triethylenetetramine (TETA), and is used for the sum of iron and copper concentration; the other which contains TETA is used only for the iron concentration. For iron determination, TETA is used as a masking agent of copper. The difference in peak height can be used for the calculation of copper concentration. Under the optimal conditions, the detection limits (3sigma) of 0.01 and 0.07 microg L(-1) were obtained for iron and copper, respectively. The proposed method can be applied to the determination of iron and copper in tap water and bottled-drinking mineral water samples. Good recoveries of the method, 98-103% for iron and 98-106% for copper, were achieved.     

Separation of microgram quantities of aluminum and iron(III)

The separation of microgram quantities of ferric iron and aluminum can be effected by passage of an acidic thiocyanate solution through the anion exchange resin Amberlite IRA-400A. The anionic complex of iron and thiocyanate remains on the column whereas aluminum passes through with the eluate. This method has been utilized in the separation of up to 200 μg of iron from comparable amounts of aluminum thus permitting the spectrophotometric determination of the latter in caustic liquors and other alkali products.     

Spectrophotometric determination of iron and cobalt with Ferrozine and dithizone

Procedures are described whereby iron (1–50 μg) and cobalt (1–25 μg) are determined spectrophotometrically, iron as iron(II) with the disodium salt of 3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine (Ferrozine) and cobalt as the cobalt(III) dithizonate complex. The reduction to iron(II) prevents interference of iron(III) in the cobalt determination, and both metals can be determined in the same portion of sample solution. Removal of interference by other metal ions is described.     

Adsorptive passivation of iron by organic acid anions

Studies on the iron passivation by organic acid anions in aqueous solutions are briefly reviewed. It is shown that the passivation can be caused only by their adsorption, retarding both the iron dissolution and the formation of oxide films. Earlier, it had been believed that oxide films play a dominant role in the iron passivation in neutral solutions. The recent viewpoint is that such nonoxide iron passivation can occur in solutions of salts of not only aromatic amino acids (sodium phenylantranilate and its substitutes), but other carboxylic acids as well. An important role of chemisorption and hydrophobic properties of anions for the formation of adsorption passive films is emphasized. New possibilities for inhibitor protection of iron against corrosion, which is based on adsorptive passivation, are pointed out.Translated from Elektrokhimiya, Vol. 40, No. 12, 2004, pp. 1503–1507.Original Russian Text Copyright © 2004 by Kuznetsov.     

Period Doubling and Chaos of Spontaneous Oscillatory Phenomena on Iron

 A new self-oscillating system introducing spontaneous oscillatory phenomena on iron in a sulfuric acid solution of hydrogen peroxide is discussed. This phenomenon can be explained by a continuous oscillation between the active and passive state of iron. Unlike other published systems that only show one-peak oscillations, the potential of iron shows highly complex dynamics: depending on the concentration of hydrogen peroxide and sulfuric acid, a period doubling and non-periodic oscillations in a self-oscillating system were observed for the first time. The reactions were analyzed by methods based on chaos theory and could finally be identified as an example of deterministic chaos.     

Mössbauer investigation of iron-aluminium mixed oxides

Mixed hydroxides of iron and aluminium have been precipitated from solutions containing iron and aluminium salts. The ratio of iron and aluminium was changed from 1:1 to 1:9. The mixed oxides produced by heating the hydroxides have been investigated by the M?ssbauer effect. The M?ssbauer spectra were composed of two systems of lines: one is due to magnetic splitting produced by alpha-Fe(2)O(3), the other is due to quadrupole splitting (0.45 mm s ) which can be assigned to iron atoms in the lattice of alpha-Al(2)O(3). The role of the anion of the solvated salts has also been investigated.     

Period Doubling and Chaos of Spontaneous Oscillatory Phenomena on Iron

Summary.  A new self-oscillating system introducing spontaneous oscillatory phenomena on iron in a sulfuric acid solution of hydrogen peroxide is discussed. This phenomenon can be explained by a continuous oscillation between the active and passive state of iron. Unlike other published systems that only show one-peak oscillations, the potential of iron shows highly complex dynamics: depending on the concentration of hydrogen peroxide and sulfuric acid, a period doubling and non-periodic oscillations in a self-oscillating system were observed for the first time. The reactions were analyzed by methods based on chaos theory and could finally be identified as an example of deterministic chaos. Received April 24, 2001. Accepted May 7, 2001     

Flow-injection analysis with the iron-induced perbromate-iodide reaction: spectrophotometric determination of iron

Total iron is determined by a flow-injection spectrophotometric technique. The production of I(-)(3) from the iron(II)- or iron(III)-induced perbromate-iodide reaction is monitored at 353 nm. Calibration graphs are linear from 10 to 100 ng/ml with correlations up to 0.9998 and can be extended up to 10 microg/ml by appropriate adjustment of conditions. The average sampling rate is 30 samples/hr. Detection limits and relative standard deviations compare well with those of other FIA methods.     

Sequential potentiometric complexometric redox determination of iron(III) and cobalt(II) with application to alloys

A simple potentiometric method is presented for successive determination of iron(III) and cobalt(II) by complexometric titration of the iron(III) with EDTA at pH 2 and 40 degrees , followed by redox titration of the cobalt(II) complex with 1,10-phenanthroline or 2,2'-bipyridyl at pH 4-5 and 40 degrees , with gold(III). There is no interference in either determination from common metal ions other than copper(II), which severely affects the cobalt determination but can be removed by electrolysis. The method has been successfully applied to determination of iron and cobalt in Kovar and Alnico magnet alloys.     

Mechanisms of antioxidant action: Time-controlled stabilisation of polypropylene by transition metal dithiocarbamates

Combinations of iron and nickel dithiocarbamates approach the ‘ideal’ delayed action photo-activators for polypropylene. They give an induction period to photo-oxidation which can be controlled by the amount of the nickel complex and a rapid rate of photo-oxidation at the end of the induction period which is primarily determined by the iron concentration. Combinations of other photo-activators and uv stabilisers show a less ideal behaviour and do not permit such accurate time control.     

Simultaneous spectrophotometric determination of humic acid and iron in water

A simple and rapid method for the determination of humic acid and iron in solution is described. Two absorbance measurements are required, one on an untreated sample aliquot, and the other on an aliquot treated to enhance iron absorptivity. The method requires sample volumes of less than 15 ml and is sensitive enough for direct application to most natural waters. Limits of detection for each component vary with concentration of the other, but 0.01 mg 1^?1 for humic acid and 0.04 μM for iron can be achieved. For six natural waters, determinations based on independent calibration curves for each component gave results 6–40$ higher for iron, and 6–29% higher for humic acid, than results obtained by the proposed method. The interference of fulvic acid and the use of different humic acid standards are examined.     

Über die verteilung von metall-8-oxychinolin-verbindungen zwischen wasser und organischen lösungsmitteln : Mitt. photometrische bestimmung des magnesiums nach extraktion seines oxinates mit chloroform bei gegenwart von aminen

Under normal conditions, magnesium oxinate does not dissolve in non-polar organic solvents. In the presence of 2% butyl amine, however, magnesium can be extracted quantitatively in the pH range 10.5–13.6 by a 0.1% oxine-chloroform solution (concentration range 0.05–10γ Mg/ml), and can be determined photometrically by measurement of the extinction at 380 mμ. This reaction has been elaborated to a specific method of determination for small quantities of magnesium in the presence of the most important other elements. Furthermore, determination of magnesium can be combined quite simply with a photometric determination of slight iron content, also as the oxinate. The practical application of the method is demonstrated by determination of magnesium and iron in several calcium minerals, aluminium alloys and a zinc alloy.     

Ion-chromatographic analysis of mixtures of ferrous and ferric iron

Determinations of the aqueous iron species Fe(II) and Fe(III) are essential for a fully-informed understanding of redox processes involving iron. Most previous methods for speciation of iron have been based on the calorimetric determination of Fe(II) followed by reduction of Fe(III) and analysis for total iron. The indirect determination of Fe(III) and the consumption of relatively large sample volumes have limited the accuracy and utility of such methods. A method based on ion-chromatography has been developed for simultaneous direct determination of Fe(II) and Fe(III). Sample pretreatment involves only conventional filtration and acidification. No interferences with the iron(II) determination were found; in determination of iron(III) the only interference observed was an artifact peak (of unknown origin) that occurred only when iron(II) was present, and had an area that was a function of the iron(II) concentration and could hence be corrected for. Solutions of iron(II) free from iron(III) can be prepared by treatment with a mixture of hydrogen and nitrogen in the presence of palladium black as catalyst, to reduce the iron(III). Photoreduction of iron(III) in acidified samples increases the Fe(II)/Fe(III) ratio; no means of circumventing this effect is known, other than storing the samples in the dark and analysing them as soon as possible.     

Flow injection determination of iron by its catalytic effect on the oxidation of 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide

A flow injection-photometric method has been developed for the determination of iron(II+III). The method is based on the catalytic effect of iron(III) on the hydrogen peroxide oxidation of 3,3',5,5'-tetramethylbenzidine to form a blue compound (lambda(max)=650 nm). In this catalyzed reaction, 1,10-phenanthroline acted as an effective activator. Iron(II) is also determined, being oxidized by hydrogen peroxide. Calibration graphs for iron(II) and iron(III) obtained under the optimized conditions were identical with each other and linear in the range 0.2-200 ng ml(-1) with a detection limit of 0.05 ng ml(-1) iron. The reproducibility was satisfactory with a relative S.D. of 1.0% for ten determinations of 5 ng ml(-1) iron(III). The proposed method was successfully applied to the determination of iron in river and lake water samples and can be determined free iron species.     

Contributions to the basic problems of complexometry-XX Determination of calcium and magnesium

A new method for the determination of magnesium in the presence of calcium is described. Calcium is masked with EGTA whilst magnesium is titrated with DCTA with Methylthymol Blue as the indicator. Calcium can be determined in the same solution by back-titration of the excess EGTA with calcium chloride solution. The usual masking agents for iron, aluminium and other heavy metals can be used.     

Simultaneous determination of iron(III) and vanadium(V) with N-phenylcinnamohydroxamic acid and thiocyanate by extraction-spectrophotometry

N-Phenylcinnarnohydroxamic acid (PCHA) reacts with iron(III) and vanadium(V) in the presence of thiocyanate to form water-insoluble orange and green complexes, respectively. The iron(III)-PCHA and vanadium(V)-PCHA-thiocyanate complexes can be quantitatively extracted into toluene and other common organic solvents at pH 1.5–2.0. The absorption spectra and composition of both complexes are described. The effects of foreign ions and of experimental variables on the extraction and determination of the two metal ions are studied. A simple, selective method is described for the simultaneous determination of iron(III) and vanadium(V) by extraction-spectrophotometry; absorbances are measured at 440 and 580 nm. Mixtures can be determined over the range 10^?4–10^?5 M in each metal. The method was applied successfully to the analysis of standard steels for iron and vanadium.     

Photo‐oxidative Stress Impacts the Expression of Genes Encoding Iron Metabolism Components in Chlamydomonas†

Chlamydomonas, like other organisms, regulates iron assimilation very tightly through differential expression of iron assimilation components. Nevertheless, in the presence of excess iron, cells do overaccumulate iron but without an evident phenotype. As iron toxicity is attributed to reactive oxygen species, we tested the impact of photon flux density (PFD) on cells with increased iron content. We noted that growth at >500 μmol m^?2 s^?1 is inhibited as iron content of the medium is increased, suggesting that high light exacerbates the systems of iron toxicity and vice versa. Cells grown in high light selectively down‐regulate the abundance of iron assimilation components, ferroxidase and FEA1, and storage protein ferritin1. At the RNA level, the abundance of ferroxidase (FOX1), iron reductase (FRE1), iron assimilatory protein (FEA1) and ferritin (FER1) mRNAs is also decreased. The time course of the response to high light compared to the response to Rose Bengal and H₂O₂ treatments suggests that both singlet oxygen and H₂O₂ may be implicated in the high light response. This hypothesis is supported by the recapitulation of some but not all of the high light responses in the carotenoid‐deficient, high light–sensitive npq1lor1 strain. We conclude that responses to iron nutrition and PFD are connected, and the determination of an optimum for photosynthetic growth for each is dependent on the other. This work defines a fourth stage of iron nutrition in Chlamydomonas, the iron excess situation, which can be molecularly and physiologically distinguished from the iron‐limited, iron‐deficient and iron‐replete stages, described previously.     

Use of 1-(2-thiazolylazo) 2-naphthol in rapid determination of iron in geological matrices

The present work describes the use of 1-(2-thiazolylazo)-2-naphthol (TAN) as a spectrophotomeric reagent for iron determination. TAN reacts with iron(II) forming a brown complex with absorption maximum at 575 and 787 nm. The following parameters were studied: complex stability, pH effect, amount of the TAN, buffer selection, amount of acetate buffer, reductor effect, order of addition of reagents and adherence to Beer's Law. The results demonstrated that iron can be determined with TAN in a pH range of 4.0-6.2 with an apparent molar absorptivity of 1.83 x 10(4) 1 . mol(-1) . cm(-1) (at 787 nm) and 1.41 x 10(4) 1 . mol(-1) . cm(-1) (at 575 nm). Beer's Law is obeyed for at least 3.00 microg/ml. The TAN reacts with other cations, but at 787 nm only the iron(II)-TAN complex absorbs. So, iron can be determined selectively in the presence of several cations. A procedure based on the direct mixture of the sample and a chromogenic solution is proposed, where iron can be determined rapidly and easily. Such procedures were used for the determination of iron in several geological matrices. No significant differences were obtained for TAN method and certificate results.     

Straightforward synthesis of amino-3-hydroxypyridin-4-one iron chelators via BBr3-mediated tandem reduction of azides and deprotection of methyl ether

A novel and straightforward BBr₃-mediated tandem reduction of organic azide and demethylation of methyl ether were described. This method provides a new approach to prepare a series of new amino-3-hydroxypyridin-4-one iron chelators, which can be used in the treatment of iron also applicable to other substrates like benzyl azides and aryl azides.     

Analytical applications of condensed phosphoric acid-I Determination of ferrous and total iron in iron ores after decomposition with condensed phosphoric acid

A simple method is described for the determination of ferrous and total iron in iron ores. Iron ores are dissolved by condensed phosphoric acid (CPA) very rapidly without any tedious and time-consuming manipulations such as elimination of silica and filtration. Under the proposed conditions (amount of sample 100 mg, amount of CPA added 10 g, heating temperature 290 degrees , heating time 30 min), magnetite, limonite and hematite are completely dissolved. The iron content can be determined in the presence of condensed phosphoric acid by titration with dichromate solution, if a slight modification is made. The total iron in iron ores, determined by the present method, is in agreement with that found by the JIS method. The ferrous iron in iron ores can be determined by dissolving the samples with CPA in a nitrogen atmosphere and titrating with dichromate solution. Chelatometric titration of iron after solvent extraction with MIBK from solutions prepared by use of CPA is found to be accurate for samples such as pyrite cinder. The ability of CPA to dissolve various materials has been investigated.