Synergetic extraction and spectrophotometric determination of gold(III)

Summary A method is described for the synergetic extraction and subsequent spectrophotometric determination of gold(III). The gold--furil dioxime-pyridine complex extracted into chloroform has a characteristic yellow colour with an absorption maximum at 330 nm. Beer's law is obeyed in the concentration range [Au(III)]45g/ 10 ml organic phase. A scheme to separate gold from interfering elements by extraction with 4-methyl-2-pentanol in benzene has been proposed.

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Zusammenfassung Ein Verfahren zur synergetischen Extraktion und nachfolgenden spektrophotometrischen Bestimmung von Gold(III) wurde beschrieben. Die Komplexverbindung des Goldes mit-Furildioxim und Pyridin ist in chloroformischer Lösung gelb gefärbt. Ihr Absorptionsmaximum liegt bei 330 nm. Bis 45g Au(III)/10 ml organischer Phase wird das Beersche Gesetz befolgt. Die Trennung des Goldes von störenden Elementen durch Extraktion mit 4-Methyl-2-pentanol in Benzol wurde vorgeschlagen.

     

Spectrophotometric and derivative spectrophotometric determination of iron by extraction of the iron(II)-TPYZ-picrate ion-association complex

A solvent extraction-spectrophotometric determination of microamounts of iron has been developed, based on the formation of an ion-association complex of iron(II) with 2,4,6-tris(2'-pyridyl)-1,3,5-triazine as primary ligand and picrate as counter-ion, which is extracted into 1,2-dichloroethane. The complex is formed at pH 4.0-7.0 and the iron concentration can be determined by measuring the absorbance directly in the organic phase. The apparent molar absorptivity is 2.2 x 10(5) l.mole(-1).cm(-1). As the method is practically free from interferences it was applied to the determination of iron in different biological and inorganic samples. Although the proposed method is very sensitive it can be further sensitized by employing the derivative spectrophotometric technique.     

Solvent extraction and spectrophotometric determination of iron(II) with 2,2′-dipyridyl-2-quinolylhydrazone

2,2′-Dipyridyl-2-quinolylhydrazone (DPQH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) reacts with DPQH at pH 3.4–4.5 to form a water-insoluble 1:2 complex, which can be extracted with many kinds of organic solvent. The extracted species with benzene has absorption maxima at 473, 504, and 644 nm and obeyed Beer's law over the range 0–14 μg of iron at 504 nm and 0–33 μg at 644 nm. The molar absorptivities at 504 and 644 nm are 3.14 × 10⁴ and 1.30 × 10⁴M^?1 cm^?1, respectively. DPQH is one of the most sensitive reagents for iron(II) and trace amount of iron(II) can be determined in the presence of fairly large amounts of other ions. Possible equilibria involved in the extraction process were also studied.     

Solvent extraction and spectrophotometric determination of iron(II) with 2,2′-dipyridyl-2-furancarbothiohydrazone

2,2′-Dipyridyl-2-furancarbothiohydrazone (DPFTH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) can be quantitatively extracted with DPFTH in benzene from aqueous solution buffered to 3.0–8.0. The extracted species has absorption maxima at 440, 477, and 738 nm and obeyed Beer's law over the range 0–40 μg of iron in 10 ml at 738 nm. The molar absorptivity at this wave length is 1.17 × 10⁴ liters mole^?1 cm^?1. The proposed method is relatively selective for iron(II) and is satisfactorily applied to the determination of the total iron in natural waters. The proton dissociation constants of the ligand determined spectrophotometrically were pK_a1 = 2.88 and pK_a1 = 6.70 at 25 °C and μ = 0.1.     

Kinetic spectrophotometric determination of traces of iron(II)

A simple method for the selective and sensitive kinetic spectrophotometric determination of iron (II) is described. The method is based on the oxidation reaction of reduced phenolphthalein by periodate in alkaline media. The change in absorbance was measured using the fixed time method. The effect of different variables on the reaction was investigated and optimum conditions were obtained. The calibration curve was linear in the range 50–3000 ng/mL, and a detection limit of 17 ng/mL was obtained. The relative standard deviation of ten replicate determinations of 200 ng/mL of Fe(II) was 1.2%. The determination of Fe(II) in the presence of a 50-fold amount of Fe(III) could be carried out. This article was submitted by the authors in English.     

Rapid extraction and direct spectrophotometric determination of iron(III) with thiothenoyltrifluoroacetone

To obtain NH₄F-HF etching agents with constant etching behaviour the concentration of NH₄OH in commercially available 40% NH₄F solutions has to be measured. By application of pH-indicators of the phenol type very small pH-deviations (0.007 pH) from the specified value (0% NH₄OH) can be measured. The specified value is simulated by the stable McIlvaine buffer. By determining the differences in optical absorption 0.01% NH₄OH can be measured in NH₄F solutions. Values found in practice are between 0.1– 0.3%.     

Indirect spectrophotometric determination of chloride by solvent extraction as tris(1,10-phenanthroline)iron(II) thiocyanate

An indirect spectrophotometric method for the determination of small amounts of chloride in fresh waters is described. Chloride ions react with mercury(II) thiocyanate to liberate thiocyanate ions, which can be selectively extracted into nitrobenzene with tris(1,10-phenanthroline)iron(II) chelate cations. The red color (516 nm) of the organic phase measured against a reagent blank is proportional to the initial concentration of chloride ions in the aqueous phase. At least an equimolar amount of tris(1,10-phenanthroline)iron(II) chelate and a 3-fold amount of mercury(II) thiocyanate are needed; the optimal pH range is 1.5–3.5. Beer's law is obeyed over the concentration range of 0.8–5.6 10^-5 M of chloride. The color stability and the apparent sensitivity are better than those of the mercury(II) thiocyanate-iron(III) method. Large amounts of sulphate, phosphate, fluoride, carbonate, acetate, potassium, sodium, and ammonium ions had negligible or no effect ; bromide, iodide, cyanide, sulphide, and thiocyanate interfere.     

Simultaneous extraction and spectrophotometric determination of cobalt(II) with thiothenoyltrifluoroacetone

Summary Thiothenoyltrifluoroacetone (1,1,1-trifluoro 4-(2-thienyl) 4-mer-captoput-en-3-2-one) is used for the simultaneous extraction and spectrophotometric determination ofg amounts of cobalt(II). 10 ml of 0.001M STTA in carbon tetrachloride quantitatively extracts, at pH 6.5, 20g of cobalt(II) as red orange colored complex which can be measured photometrically at 490 nm. The system conforms to Beer's law in the concentration range of 0.5–6.0g/ml of Cobalt(II). Studies on the effect of varying volume and concentration of the reagent, stability of the complex, and the period of equilibration were also reported. It is possible to extract and determine cobalt(II) quantitatively in the presence of large number of cations and anions. The method can be made selective by making use of appropriate masking agents.

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Zusammenfassung Thiothenoyltrifluoraceton [1,1,1-Trifluor-4 (2-thienyl)-4-mercaptobuten-3-2-on] (STTA) wurde für die gleichzeitige Extraktion und spektrophotometrische Bestimmung von Mikrogrammengen Kobalt(II) verwendet. 10 ml einer 0,001-m STTA-Lösung in Tetrachlorkohlenstoff extrahieren bei pH6,5 quantitativ 20g Co(II) als rotorangen Komplex, der bei 490 nm photometrisch gemessen werden kann. Zwischen 0,5 und 6,0g Co/ml ist das Beer'sche Gesetz erfüllt. Der Einfluß von Volumen und Konzentration des Reagens, die Stabilität der Komplexverbindung und die Extraktionsdauer wurden untersucht. Kobalt läßt sich so in Gegenwart vieler Kationen und Anionen quantitativ extrahieren und bestimmen. Bei Anwendung geeigneter Markierungsmittel ist die Methode selektiv.

     

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.     

Micro-fusion and spectrophotometric determination of iron(II) and iron(III) in chrome spinels and other refractories

Spectrophotometric determination of FeO in milligram samples of chrome spinels and related refractory minerals after high-frequency micro-fusion with lithium tetraborate in an inert atmosphere is described. Anomalous responses (apparent reduction or oxidation of FeO depending on the ferroïn-type reagent)_rendered the procedure highly unreliable. All the fluxes containing structural oxygen, as well as phosphoric acid, acted as oxidants even when atmospheric oxidation was rigorously excluded. However, the method is suitable for micro-determination of total iron in spinels. Spectrophotometric measurements gave an average relative standard deviation of 0.73%.     

Sequential flow-injection spectrophotometric determination of iron(II) and iron(III) by copper(II)-catalyzed reaction with Tiron

A flow injection method for the sequential determination of iron(II) and iron(III) was developed. It is based on the differential reaction kinetics of iron(II) and iron(III) with Tiron in a double-injection FI system. The proposed method employs the accelerating action of copper(II) for the oxidation of iron(II) in the presence of Tiron. A linear calibration graph is obtained for iron (II) and iron(III) in the concentration range 1.8 × 10^–5– 1.8 × 10^–4 mol/L; the throughput of samples is 30 injections/h. Received: 22 October 1996 / Revised: 4 December 1996 / Accepted: 10 December 1996     

Sequential flow-injection spectrophotometric determination of iron(II) and iron(III) by copper(II)-catalyzed reaction with Tiron

A flow injection method for the sequential determination of iron(II) and iron(III) was developed. It is based on the differential reaction kinetics of iron(II) and iron(III) with Tiron in a double-injection FI system. The proposed method employs the accelerating action of copper(II) for the oxidation of iron(II) in the presence of Tiron. A linear calibration graph is obtained for iron (II) and iron(III) in the concentration range 1.8 × 10^–5– 1.8 × 10^–4 mol/L; the throughput of samples is 30 injections/h.     

Simultaneous derivative spectrophotometric determination of cobalt(II) and nickel(II) by dithizone without extraction

Dithizone (Dz), a common extractive-photometric ligand for Co(II) and Ni(II), has been dissolved in the water-miscible solvent tetrahydrofurane (THF) so as to constitute a reagent for both metals in aqueous phase without extraction. Complex formation was complete for both metals at pH 12.0 (adjusted by aqueous NH(3)) within 30 min, and the complexes were stable for at least 2 h. First-derivative spectra of the metal dithizonates (singly or as binary mixtures) were preferred to ordinary spectra, because working wavelength determination was more precise and spectral overlap was less. Two wavelengths at which the spectral overlap was minimum were selected as analytical wavelengths, i.e. 620 nm for Co and 740 nm for Ni, and the calibration curves drawn with zero-to-peak values as a function of concentration were linear for these wavelengths. Thus, the total (1)D values at 620 and 740 nm of the mixtures were used to determine Co and Ni concentrations. The relative standard deviation (R.S.D.) for the analysis of Co (3.0 mg l(-1)) individually was 3.5%, and for its admixture with Ni (3.5 mg l(-1)) was 2.5%. The R.S.D. for the analysis of Ni (5.9 mg l(-1)) individually and for its admixture with Co (1.8 mg l(-1)) were 5.5 and 5.8%, respectively. The linear range in (1)D evaluation was between 5.0x10(-6) and 1.0x10(-4) M for Co and 2.0x10(-5)-2.0x10(-4) M for Ni. Interference analysis was performed for individual metal (Co or Ni) determinations. Finally, the method has been applied to a Ni-Cr-based dental alloy (Wiron 99) successfully.     

The spectrophotometric determination of cobalt by extraction of triphenylsulphonium tetrathiocyanatocobaltate(II)

Cobalt (0–130 μg) can be determined spectrophotometrically at 625 nm after its extraction as triphenylsulphonium tetrathiocyanatocobaltate(II) into 1:4 acetone/1,2-dichloroethane at pH 7. The effects of pH, diverse ions and masking studies are reported. The method is applied to the determination of cobalt (0.2–10.05) in high-speed tool steels without prior separation of iron, and in vitamin B12.     

Sequential determination of iron(II) and iron(III) in pharmaceutical by flow-injection analysis with spectrophotometric detection.

A flow injection procedure for the sequential spectrophotometric determination of iron(II) and iron(III) in pharmaceutical products is described. The method is based on the catalytic effect of iron(II) on the oxidation of iodide by bromate at pH = 4.0. The reaction was monitored spectrophotometrically by measuring the absorbance of produced triiodide ion at 352 nm. The activating effect for the catalysis of iron(II) was extremely exhibited in the presence of oxalate ions, while oxalate acted as a masking agent for iron(III). The iron(III) in a sample solution could be determined by passing through a Cd-Hg reductor column introduced in the FIA system to reduce iron(III) to iron(II), which allows total iron determination. Under the optimum conditions, iron(II) and iron(III) could be determined over the range of 0.05 - 5.0 and 0.10 - 5.0 microg ml(-1), respectively with a sampling rate of 17 +/- 5 h(-1). The experimental limits of detection were 0.03 and 0.04 microg ml(-1) for iron(II) and iron(III), respectively. The proposed method was successfully applied to the speciation of iron in pharmaceutical products.     

Liquid-liquid extraction and spectrophotometric determination of palladium(II) and ruthenium (III) with isonitrosoethylbenzoylacetate

Summary A method is described for the extractive spectrophotometric determination of palladium or ruthenium (III) using isonitrosoethylbenzoylacetate as the reagent. The yellow Pd-INEBA complex extracted into chloroform absorbs at 410 nm and conforms to Beer's law in the range of 10–110g of Pd per 10 ml of organic phase. The purple Ru-INEBA complex extracted into MIBK absorbs at 500 nm and conforms to Beer's law in the range of 25–125g of Ru per 10 ml of organic phase. The method affords the determination of both Pd and Ru in the presence of large number of cations and anions.

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Flüssig-flüssig-Extraktion und spektrophotometriscbe Bestimmung von Palladium(II) und Ruthenium(III) mit Isonitrosoäthylbenzoylacetat (IÄBA)

Zusammenfassung Eine Methode für die Extraktion und spektrophotometrische Bestimmung von Pd oder Ru mit IÄBA wurde beschrieben. Der gelbe Pd-Komplex absorbiert in chloroformischer Lösung bei 410 nm und entspricht dem Beerschen Gesetz für 10–110g Pd/10 ml organische Phase. Der rote Ru-Komplex absorbiert in MIBK bei 500 nm und entspricht dem Beerschen Gesetz für 25–125g Ru/10 ml. Das Verfahren eignet sich für die Bestimmung der beiden Metalle in Gegenwart zahlreicher Kationen und Anionen.

     

The spectrophotometric and fluorimetric determination of cobalt by extraction as protriptylinium tetrathiocyanatocobaltate(II)

Cobalt can be determined by spectrophotometric or fluorimetric measurements after its extraction as protriptylnium tetrathiocyanatocobaltate(II) into 1 : 1 acetone—chloroform. The effects of pH and diverse ions are reported and the system is applied to the determination of 0.002–0.2% cobalt in mild steels without prior separation of the iron.