Volumetric determination of small amounts of uranium : Chromous chloride as reducing agent

A volumetric method is proposed for the rapid determination of small amounts of uranium. The hexavalent uranium is reduced to the quadrivalent state by chromous chloride, the excess of which is destroyed by air oxidation. A low potential redox indicator is used to follow the reduction and air oxidation. Ferric sulphate is added to the solution and the resulting ferrous ion titrated with dichromate solution.     

99mTc-labelled compounds prepared with tungsten(III) as the reducing agent

The application of K₃W₂Cl₉ as reducing agent in preparation of^99mTc-labelled compounds is described. Pertechnetate reduction was carried out in solutions of pH 2 and also of pH 5.5. DTPA, citrate, gluconate, HEDSPA and MDP were successfully labelled. Two types of labelled gluconate complexes were obtained. Complex I exhibited in rats an increased^99mTc affinity to kidneys (21%). Complex II exhibited an increased^99mTc affinity to bone (8.7%). Two types of labelled HEDSPA preparations were obtained: one yielded 29%^99mTc activity in bone, the other type exhibited only 13.4%. The results indicated the absence of mixed complexes.     

Oxidimetric determination of indigo with iron(III) and hexacyanoferrate(III)

The use of iron(III) in sulphuric acid medium and of potassium hexacyanoferrate(III) in hydrochloric acid medium has been investigated for the oxidimetric determination of indigo and indigo sulphonic acid. Conditions have been established for the assay of the dye with iron(III) sulphate at 100 degrees and with potassium hexacyanoferrate(III) at room temperature.     

Photometric determination of iron (III)

A sensitive colored reaction of tiron with iron (III) is described. It is based on a complex formation between tiron and iron (III) in basic medium. The method is suitable to determine 0.4–10 ppm of iron (III) with a relative standard deviation of 0.45–1.4% depending on the concentration level, molar absorptivity of 5.7 × 10³ liter mol⁻¹ cm⁻¹, and Sandell sensitivity index of 0.0098 μg/cm².Because of being simple and rapid, this method can certainly be used in routine analysis.     

Diformylhydrazine as analytical reagent for spectrophotometric determination of iron(II) and iron(III)

The bidentate ligand diformylhydrazine (OHC-HN-NH-CHO), DFH, combines with iron(II) and iron(III) in alkaline media in the pH range 7.3-9.3 to form an intensely colored red-purple iron(III) complex with an absorption maximum at 470 nm. Beer's law is obeyed for iron concentrations from 0.25 to 13 microg mL(-1). The molar absorptivity was in the range 0.3258x10(4)-0.3351x10(4) L mol(-1) cm(-1) and Sandell's sensitivity was found to be 0.0168 microg cm(-2). The method has been applied to the determination of iron in industrial waste, ground water, and pharmaceutical samples.     

Polarographic determination of iron(II) and iron(III) complexes with edta

The iron(II) and iron(III) complexes with EDTA can be determined separately and in mixtures in acetate-buffered medium at pH 4.0. The E_{$\text{1}\text{2}$}values are in the range ?0.105 to ?0.112 V vs. SCE. Linear calibration plots are obtained over the range 0–1.0 mM for each oxidation state. A sample-handling procedure for avoiding oxidation of iron(II) species is described. It is shown that the acetate buffer system does not affect the stability of the iron-EDTA complexes.     

Spectrophotometric determination of iron(III) with EDTA tetrahydrazide

The tetrahydrazide of ethylenediamine tetraacetic acid (NH₂NH)₄-EDTA was synthesized from the EDTA ester and hydrazine hydrate in ethanolic solution, the resulting (NH₂NH)₄-EDTA being recrystallized in 60% ethanol. When the spectrophotometric study of the iron(III) (NH₂NH)₄-EDTA complex in aqueous solution was made two absorption maxima at 530 and 450 nm at pH 4.5 and 11.0, respectively, were found. Beer's law is obeyed in the range 1.0–20.0 μg Fe(III) ml^?1 at 530 nm and pH 4.5 and 0.5–12.0 μg Fe(III) ml^?1 at 450 nm and pH 11.0, the molar absorptivities being 1.95 × 10³ 1 mol^?1 cm^?1 at 530 nm and 3.35 × 10³ 1 mol^?1 cm^?1 at 450 nm, respectively. The Ringbom optimal interval falls between about 3 and 18 μg Fe(III) ml^?1 at 530 nm and about 2–14 μg Fe(III) ml^?1 at 450 nm. The reaction between the metal and the ligand was also investigated. The method has been successfully applied to the determination of iron in talcs.     

Volumetric titration of iron (III)-salts with disodium EDTA, using FeII-cacotheline as indicator

Summary A volumetric method has been developed for the determination of iron (III) with disodium EDTA, using a mixture of cacotheline and iron(II) as indicator. The titration of the iron (III) salt is carried out in a buffered solution ofph 4–5 in carbon dioxide atmosphere with magnetic stirring, until a pink color appears. The pink color is due to the reduction of cacotheline by ferrous-EDTA. The reduction occurs only when all the iron (III) is complexed by EDTA. The end point is sharp and the method has been found to give results accurate to±0.3 to±0.5 percent.     

Colorimetric determination of iron (III) with 1,10-phenanthroline

Summary A new procedure has been developed for the colorimetric determination of iron(III). It consists in the reduction of iron (III) in dilute sulphuric acid medium (0.1 to 1.0 N) with an excess of hypophosphite (1100) at room temperature using one or two drops of 0.1% PdCl₂ solution as catalyst, and then complexing the reduced iron with 1.10-phenanthroline.Iron (III) can also be reduced with phosphite using the PdCl₂ catalyst and boiling for 5 to 10 min on a hot plate. The molar concentration of phosphite is preferably kept 500 times that of ferric ion.

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Zusammenfassung Es wurde ein neues Verfahren zur colorimetrischen Bestimmung von Eisen(III) ausgearbeitet. Dabei wird das Eisen in verd. Schwefelsäure (0,1–1,0 n) mit einem Überschuß von Hypophosphit (1100) bei Zimmertemperatur unter Verwendung von ein oder zwei Tropfen 0,1%iger PdCl₂-Lösung als Katalysator reduziert und anschließend das zweiwertige Eisen mit 1,10-Phenanthrolin umgesetzt.Eisen(III) kann auch mit Phosphit reduziert werden, wenn man ebenfalls PdCl₂ als Katalysator verwendet und 5–10 min erhitzt. Die molare Konzentration des Phosphits soll dabei das 500fache von der des Eisens betragen.

     

Selective spectrophotometric determination of iron(III) with EDTA

A spectrophotometric determination of iron as its iron (III)-EDTA-H₂O₂-NH₃ complex is described; up to 10-fold amounts of metals that form EDTA complexes absorbing at the same wavelength do not interfere because hydrogen peroxide reacts with thciron(IIl)-EDTA complex but does not affect the EDTA complexes of coppcr(II), nickel(II), cobalt(ltl) and chromium(Ilt).     

Spectrophotometric determination of iron(III) with 3-thianaphthenoyltrifluoroacetone

Summary 3-Thianaphthenoyltrifluoroacetone has been proposed for the spectrophotometric determination of iron(III). The 31 complex is very stable and can be extracted from acid solution into chloroform. Beer's law is obeyed and the molar extinction coefficient is 5.0·10³ at 516 nm. Relatively large amounts of cobalt, nickel and copper are tolerated. The method is simple, convenient and reproducible.

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Zusammenfassung 3-Thianaphthenoyltrifluoraceton wurde für die spektrophotometrische Eisen(III)-bestimmung vorgeschlagen. Der 31-Komplex ist sehr beständig und läßt sich aus saurer Lösung mit Chloroform extrahieren. Die Farbe entspricht dem Beerschen Gesetz, die molare Extinktion beträgt 5,0·10³ bei 516 nm. Relativ große Mengen Kobalt, Nickel und Kupfer stören nicht.

     

Volumetric determination of uranium in a mixture of uranium and plutonium employing Fe(III) as titrant

Summary A method for the determination of U in the presence of Pu based on the reduction of U to U(IV) and Pu to Pu(III) by zinc amalgam followed by oxidimetry of U(IV) has been developed. Fe(III) perchlorate was chosen as the most suitable titrant for the selective oxidation of U(IV) as conventional oxidising titrants fail in the presence of Pu(III). The potentiometric titration of U(IV) with Fe(III) is known to be slow. This problem, however, has been overcome by selecting a suitable buffer medium and complexing agent to alter the potentials of the Fe(III)/Fe(II) and U(VI)/U(IV) systems in the favourable direction. Results of the titration of U(IV) with Fe(III) at pH 2 in the presence of ferrozine as complexing agent for Fe(II) are summarized. R.S.D. obtained for twenty determinations of 3–5 mg of U was 0.3 % in the presence of 1–4 mg of Pu.

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Volumetrische Bestimmung von Uran in einem U/Pu-Gemisch mit Hilfe von Fe(III)

Zusammenfassung Das Verfahren beruht auf der Reduktion von U zu U(IV) und Pu zu Pu(III) mit Hilfe von Zinkamalgam und anschließender Titration mit Fe(III)-perchlorat. Dieses Reagens hat sich für die selektive Oxidation des U(IV) am besten bewährt, da andere Oxidationsmittel in Gegenwart von Pu(III) versagen. Die Endpunktsindikation erfolgt potentiometrisch, wobei die an sich langsame Einstellung des Endpunktes dadurch beschleunigt wird, daß durch Zusatz eines geeigneten Puffers und eines Komplexierungsmittels (Ferrozin) für Fe(II) die Redoxpotentiale von Fe(III)/Fe(II) und U(VI)/U(IV) entsprechend verschoben werden. Die relative Standardabweichung für die Bestimmung von 3–5 mg U in Gegenwart von 1–4 mg Pu liegt bei 0,3%.

     

Spectrophotometric determination of trace amounts of iron(III) with norfloxacin as complexing reagent

The complexation of iron(III) with norfloxacin in acidic solution at 25 degrees C, at an ionic strength of about 0.3 M and a pH of 3.0 has been studied. The water-soluble complex formed, which exhibits an absorption maximum at 377 nm, was used for the spectrophotometric determination of trace amounts of iron(III). The molar absorptivity was 9.05 x 10(3) I mol-1 cm-1 and the Sandell sensitivity 6.2 ng cm-2 of iron(III) per 0.001 A. The formation constant (Kf) was determined spectrophotometrically and was found to be 4.0 x 10(8) at 25 degrees C. The calibration graph was rectilinear over the range 0.25-12.0 p.p.m. of iron(III) and the regression line equation was A = 0.163c - 0.00042 with a correlation coefficient of 0.9998 (n = 9). Common cations, except cerium (IV), did not interfere with the determination. The results obtained for the determination of iron(III) using the described procedure and the thiocyanate method were compared statistically by means of the Student t-test and no significant difference was found.     

Flow injection spectrophotometric determination of formaldehyde based on its condensation with hydroxylamine and subsequent redox reaction with iron(III)-ferrozine complex

A flow injection (FI) spectrophotometric method is proposed for the determination of low concentration of formaldehyde (HCHO) in liquid media. It is based on the condensation of HCHO with hydroxylamine sulfate, followed by the reduction reaction of iron(III)-ferrozine complex with the residual hydroxylamine to form a purple iron(II)-ferrozine complex (λ_max = 562 nm). In the first reaction, hydroxylamine decreases proportionally to the concentration of HCHO, and therefore the produced purple iron(II)-ferrozine complex decreases with increasing HCHO (a negative FI peak is obtained). The detection limit (S/N = 3) was 1.6 μg L⁻¹. The method can be applied to the determination of HCHO in industrial wastewater.     

Fluorimetric determination of iron(III) by a kinetic method

A sensitive and relatively interference-free method for the kinetic determination of iron(III) is described. The method is based on the catalytic action of this ion on the autoxidation process of 4,8-diamino-1,5-dihydroxyanthraquinone-2,6-disulfonate (disodium salt), to produce a strong pink fluorescence that increases with time. The reaction is monitored at 585 nm, when excited at 525 nm, and the initial rate method is applied to perform the analytical procedure. The influence of reaction variables and the effect of foreign ions are discussed. Iron(III) contents between 0.1 and 1 μg ml^?1 can be determined with R.S.D. of ± 3.7%.     

Flow-injection determination of iron(II), iron(III) and total iron with chemiluminescence detection

Iron(II) (1.0 × 10^?9–1.0 × 10^?6 M) is determined by the production of chemiluminescence in a luminol system in the absence of added oxidant. Iron(III) (2.0 × 10.8^?8–2.0 × 10^?6 M) is determined after reduction to iron(II) in a silver reductor mini-column in the flow system. Cobalt, chromium, copper and manganese interfere.