Improved spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol in the presence of benzyldimethylstearyltrimethylammonium chloride

An improved spectrophotometric determination of uranium(VI) is proposed using 4-(2-pyridylazo)resorcinol(PAR) in the presence of benzyldimethylstearyltrimethylammonium chloride(BSTAC) as a cationic surfactant. The calibration graph is linear in the range of 0.3–60 g/10 ml uranium(VI), measuring the absorbance at 550 nm. The reproducibility for 19.0 g/10 ml uranium(VI) is 0.57%. The third-derivative method using the third-derivative distance (d³A/d³) among ₁ 530 nm, ₃ 594 nm and ₂ 565 nm was also investigated.     

Improved spectrophotometric determination of osmium(VIII) with 4-(2-pyridylazo) resorcinol in mixed surfactants

The colour development between 4-(2-pyridylazo)-resorcinol(PAR) and osmium(VIII) in the presence of cationic and nonionic surfactants in a weakly acidic medium was more stable and reproducible than in the absence of surfactant (PAR-alone method). An improved spectrophotometric determination of osmium(VIII) with PAR was investigated in the presence of mixed surfactants of N-hexadecyltrimethylammonium chloride (HTAC) and Brij 58 [poly(oxyethylene)lauryl ether] as cationic and nonionic surfactants at pH 6.0-7.2. The calibration graph was linear in the range 0-110 microg/10 ml osmium(VIII), and the apparent molar absorptivity was 2.4 x 10(4) l.mole(-1).cm(-1) with a Sandell sensitivity of 0.0079 microg/cm(2) osmium(VIII).     

Extraction and spectrophotometric determination of gallium with 4-(2-pyridylazo)resorcinol

A sensitive and selective spectrophotometric determination of gallium is described. It is based on extraction of gallium from 3 M hydrochloric acid solution as a chloro-complex into 1,2-dichlorobenzene and exchange of the chloro ligand with 4-(2-pyridylazo)resorcinol (PAR); the final association complex of Ga—PAR with tetraphenylarsonium ions is measured in the organic phase. The absorption maximum occurs at 510 nm and the effective molar absorptivity is (8.2 ±0.3) ·1O⁴ l mol^-1cm^-1. Beer's law is obeyed over the range 0.2–2 p.p.m. of gallium. Few ions interfere.     

Characterization of complexes involved in the spectrophotometric determination of cobalt with 4-(2-pyridylazo)resorcinol

Complex species involved in the spectrophotometric determination of cobalt with 4-(2-pyridylazo)resorcinol (PAR = H₂R) were studied in solution and in the solid state. An anionic [Co(III)R₂]^- species was extracted from aqueous solution in chloroform by tetraphenylarsonium or tetraphenylphosphonium chloride. Stable tetraphenylarsonium and tetraphenylphosphonium salts of di-4-(2-pyridylazo)resorcinolo cobaltate(III) with the formula [(C₆H₅)₄X][Co(III)R₂] where X=As.P; and R=C₁₁H₇N₃O₂^2-, were isolated from the chloroform phase. The complexes were characterized by elemental analyses, visible, i.r., p.m.r., e.s.r. spectra, x-ray powder photographs, magnetic susceptibility and conductivity measurements. The spectral evidence and magnetic properties indicate a tridentate coordination of two 4-(2-pyridylazo) resorcinol dibasic anions, bonded to cobalt(III) in a symmetric arrangement with both azo groups coordinated to the cobalt atom through a single nitrogen lone pair.     

Spectrophotometric determination of thallium with 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol

Thallium(III) gives sensitive reactions with PAR and TAR (epsilon = 2 x 10(4) at 520 nm), forming 1:1 complexes at pH approximately 1-2, and a mixture of 1:1 and 1:2 complexes at higher pH values; hydrolysis sets in above pH approximately 3. The stability constants are evaluated.     

Spectrophotometric determination of palladium with 4-(2-pyridylazo)resorcinol

Summary A simple photometric method for the determination of palladium has been worked out, employing pyridylazo-resorcinol (PAR) as a complexing ligand for the metal ion. The coloured species is extractable into chloroform in the presence of diethylamine, the absorbance of which is measured at 535 nm. The method is free from the interference of a large number of elements particularly the other platinum metals. It obeys Beer's law in the range of 0–3 g Pd/ml with Sandell's sensitivity of 0.0034 g Pd cm^–2. The ratio of metal to ligand in the complex is found to be 1:1. Analysis of various samples has been carried out with satisfactory and reproducible results (standard deviation ±0.002).     

An extraction-spectrophotometric determination of palladium with 4-(2-pyridylazo)resorcinol in the presence of diphenylguanidine

A new, sensitive spectrophotometric determination of palladium has been developed, based on the extraction of the red Pd(II) chelate with 4-(2-pyridylazo)resorcinol in the presence of N,N′-diphenylguanidine into n-butanol; the sensitivity of the method according to Sandell is S = 1.12 μg cm^?2, ?₅₃₀ = 9.4 × 10⁴ liters mol^?1 cm^?1, and palladium can be determined at concentrations from 0.21 to 1.91 μg ml^?1.     

Spectrophotometric determination of niobium in zirconium with 4-(2-pyridylazo)resorcinol

The direct spectrophotometric determination of niobium in zirconium alloys with 4-(2-pyridylazo)resorcinol is described. Samples are dissolved in hydrofluoricsulphuric acid mixture and the colour developed without the removal of fluoride. In the presence of EDTA only Co²⁺, Ta⁵⁺ and V⁵⁺ cause serious interference. The molar absorptivity is 3.67 .10⁴ in the presence of 1 /smg of zirconium, and Beer's law is obeyed up to 1.0μg Nb/ml. The method can be applied to zirconium alloys containing as little as 0.005% niobium.     

Multiwavelength spectrophotometric determination of protolytic constants of 4-(2-pyridylazo) resorcinol (PAR) in binary DMF-water mixtures

A multiwavelength spectrophotometric titration method was applied to study the protolytic constants of 4-(2-pyridylazo) resorcinol(PAR), in binary DMF + water mixtures. UV-vis absorption spectra of PAR solution were recorded in the course of pH-metric titration of acidic solutions of PAR with standard base solution. The protolytic equilibrium constants, spectral profiles, concentration diagrams and also the number of components have been calculated from the fitting of the pH-spectral titration data with appropriate mass balance equations by a home written program according to an established target factor analysis. To precise determination of number of absorptive components a recently developed statistical indicator function (IND function) was used. A glass electrode calibration procedure based on a four-parameter equation pH=α+SpcH+JH⁺[H⁺]+JOH⁻Kw/[H⁺] based on the Gran's plots was used to obtain pH readings in the concentration scale (p_cH). It has been observed that there is an inverse relationship between second and third protolytic constants and mole fraction of DMF. The effect of the solvent on the protolytic constants was discussed.     

Spectrophotometric determination of uranium(VI) with 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol in the presence of anionic surfactant

A highly sensitive method for spectrophotometric determination of uranium has been devised. The method is based on formation of a red-violet 1:2 (metal:ligand) complex from the reaction of uranium(VI) with 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol (3,5-diBr-PADAP) in the presence of an anionic surfactant, sodium lauryl sulphate. Its molar absorptivity is found to be 9.1 x 10(4)l.mole(-1).cm(-1). The absorbance is constant in the range pH 8.4-9.9 Beer's law is obeyed for 0-1.4 mug/ml concentrations of uranium. In the presence of DCTA the method is selective for uranium, and can be used for the determination of trace amounts of uranium in water samples.     

A study of the direct spectrophotometric determination of uranium(VI) in trialkylamine extracts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

A straightforward spectrophotometric method is described for the determination of uranium(VI) in trialkylamine sulphate extracts in kerosene diluent; 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) is used for colour formation without resort to backextraction into an aqueous phase. The method provides good tolerance to sulphate ion and rapid colour development and appears to be free from interference when applied to extracts from uranium sulphate leach liquors.     

Liquid-liquid extraction and cloud point extraction for spectrophotometric determination of vanadium using 4-(2-pyridylazo)resorcinol

Liquid-liquid extraction (LLE) and cloud point extraction (CPE) of vanadium(V) ternary complexes with 4-(2-pyridylazo)resorcinol (PAR) and 2,3,5-triphenyl-2H-tetrazolum chloride (TTC) were investigated. The optimal conditions for vanadium extraction and spectrophotometric determination were identified. The composition (V: PAR: TTC) of the extracted species was 1:2:3 (optimal conditions; LLE), 2:2:2 (low reagents concentrations; LLE), 1:1:1 (short heating time;CPE), and 1: 1: 1 + 1: 1: 0 (optimal extraction conditions; CPE). LLE, performed in the presence of 1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid and NH₄F as masking agents, afforded the sensitive, selective, precise, and inexpensive spectrophotometric determination of vanadium. The absorption maximum, molar absorptivity, limit of detection, and linear working range were 559 nm, 1.95 × 10⁵ dm³ mol^?1 cm^?1,0.7 ng cm^?3, and 2.2–510 ng cm^?3, respectively. The procedure thus developed was applied to the analysis of drinking waters and steels. The relative standard deviations for V(V) determination were below 9.4 % (4–6 × 10^?7 mass %; water samples) and 2.12 % (1–3 mass %; steel samples).     

Extraction—spectrophotometric determination of copper(II) with 4-(2-pyridylazo)resorcinol and a long-chain quaternary ammonium salt

A simple and highly sensitive extraction—spectrophotometric determination of copper (II) is described. The ion-associate formed between the copper(II)—4-(2-pyridylazo)-resorcinol (PAR) anion and tetradecyldimethylbenzylammonium chloride (TDBA) is extracted with chloroform at pH 9.7. The absorption maximum of the extracted species occurs at 510 nm, the molar absorptivity being 8.05 (± 0.07) × 10⁴ l mol^-1 cm^-1. Beer's Law is obeyed in the concentration range 0.1–0.5 μg Cu ml^-1. The composition of the ion-associate is estimated to be [Cu(PAR)₂(TDBA)₂]. The conditional extraction constant is log K'_ex ≈ 8. The interference of some cations and anions is studied. The method is suitable for analysis of waters.     

Solid-phase spectrophotometric determination of trace amounts of vanadium at sub-ng/ml level with 4-(2-pyridylazo)resorcinol

Solid-phase spectrophotometry has been applied to analysis for trace amounts of vanadium. Vanadium was sorbed in a styrene-divinylbenzene-type anion-exchanger Dowex 1-X8 as a vanadium-4-(2-pyridylazo)resorcinol complex. Resin phase absorbances at 562 and 800 nm were measured directly which allowed the determination of vanadium in the range of 0.1-2.4 ng/ml with a RSD of 1.5%. The method has been applied to the determination of vanadium in different samples, namely toadstool tissue, mussel tissue, petroleum crudes and swamp water.     

Application of experimental design for investigating the differential spectrophotometric determination of large amounts of niobium with 4-(2-pyridylazo)resorcinol

Differential spectrophotometry is used to determine large amounts of niobium in the alkali metal/niobium/fluoride mixes involved in the electrolytic separation of pure niobium. In tartrate medium, niobium forms a purple mixed-ligand complex with 4- (2-pyridylazo) resorcinol (PAR). The pH range for constant absorbance found, for two tartrate concentrations, is 6.1 ± 0.05; outside this pH range, the absorbance is strongly affected by small changes of pH. The optimum concentrations of tartrate and PAR for the differential method were found by means of experimental design. A quadratic polynomial model was applied; the results obtained were also used to calculate the stability constants of the coloured complexes. Comparison of the variation of these constants with changes in the absorption spectra of the solutions and with changes in the empirical response surfaces provided an explanation of the inadequacy of the calculated polynomial; several tartrate complexes and mixed ligand complexes of niobium appeared in some parts of the investigated factor space. The differential spectrophotometric procedure developed allows determination of 10–30% niobium with a relative standard deviation of 0.0025; its accuracy is proved by the determination of niobium in the stoichiometric compound K₂NbF₇.     

Extraction—spectrophotometric determination of traces of cadmium with 4-(2-pyridylazo)resorcinol and a long-chain quaternary ammonium salt

A simple and highly sensitive extraction—spectrophotometric determination of cadmium is described. The ion-associate formed between the cadmium-PAR anionic chelate and cetyldimethylbenzylammonium chloride (CDBA) is extracted with chloroform at pH 10. The absorption maximum of the extracted species occurs at 505 nm, the molar absorptivity being (9.82 ± 0.30) × 10⁴ l mol^-1 cm^-1. The optimal concentration range for measurements is 0.2–1.0 μg Cd ml^-1; Beer's law is obeyed. The composition of the ion-associate is estimated to be CdPAR₂-2CDBA. The conditional extraction constant is log K'_ex ≈ 8. The stability constant of the cadmium—PAR chelate in aqueous solution is log β₂ = 17.5 ± 0.3. Extraction with N-benzoyl-N-phenylhydroxylamine is used to avoid several interferences. Moderate amounts of zinc are masked with sodium hydroxide.     

A study of the spectrophotometric method for the determination of uranium(VI) in trialkylamine/kerosene extracts using 1-(2-pyridylazo)-2-naphthol

Summary The Spectrophotometric method for the determination of uranium(VI) in trialkylamine extracts using 1-(2-pyridylazo)-2-naphthol (PAN) as a colorimetric reagent has been examined. The Job and Mole Ratio methods suggest that the coloured product is a 11 complex of uranium and PAN. The method can be applied to cover the concentration range 0 to 5 g uranium per litre of extract. Sulphate interference is eliminated in the method by removal with calcium ions before colour development. Interferences from other ions likely to be present in the aqueous liquor appear to arise largely from inhibition of the uranium partition into the amine phase.

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Untersuchung der spektralphotometrischen Uran(VI)-Bestimmung in Trialkylamin/Kerosin-Extrakten mit Hilfe von 1-(2-Pyridylazo)-2-naphthol

Zusammenfassung Das Verfahren, bei dem ein Uran-PAN-Komplex der Zusammensetzung 11 gebildet wird, kann für einen Konzentrationsbereich von 0 bis 5 g U pro l Extrakt eingesetzt werden. Eine Störung durch Sulfat wird durch dessen Entfernung mit Calciumionen vor der Farbentwicklung verhindert. Störungen durch andere Ionen werden hauptsächlich durch Beeinflussung der Uranextraktion hervorgerufen.