Adsorption voltammetry of the vanadium-2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) system

The behaviour of the vanadium(V) complex with 5-Br-PADAP at a mercury electrode was investigated in HOAcNaOAc. The adsorption phenomena were observed by linear-sweep voltammetry. The mechanism of the electrode reaction was found to be the irreversible reduction of the V(V) in the complex adsorbed on the surface of the electrode to the V(IV) complex with 5-Br-PADAP. In 0.02 mol l^?1 HOAc-0.012 mol l^?1 NaOAc (pH 4.5) and 1 × 10^?6 mol l^?1 5-Br-PADAP, the detection limits of linear-sweep adsorption voltammetry and 1.5th-order derivative adsorption voltammetry are 5 × 10^?10 and 2.5 × 10^?11 mol l^?1 , respectively. The method was applied to samples of ore (Geological Deposit).     

Spectrophotometric determination of cadmium(II) using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

The complex of cadmium with the reagent 2-(-5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) has been studied. The composition, stability constant, and free energy change of formation of the complex have been determined. A sensitive spectrophotometric method for the determination of cadmium has been developed and applied for a range of concentration of 0.4–4.0 μg/ml cadmium using the complex Cd-5-Br-PADAP. The optimum conditions for maximum sensitivity of determination such as standing time, pH, wavelength, and order of addition have been determined. The effect of foreign ions on this method has been also studied.     

Sensitive spectrophotometric determination of nickel(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

A simple, selective and highly sensitive procedure for spectrophotometric determination of nickel has been developed. At pH 5.5, nickel reacts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in water-ethanol medium to form a red-violet complex which has two absorption maxima, at 520 and 56Onm. The molar absorptivity at 56Onm is 1.26 x 10(5) l.mole(-1).cm(-1). Beer's law is obeyed for 0-15 mug of nickel. Nickel in aluminium alloys and electroplating waste-water has been determined by this method.     

Rapid spectrophotometric determination of zirconium with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

Zirconium reacts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the pH range 3.8-5.8 to form a red chelate that is soluble in methanol-water mixtures. The absorbance of the 1:3 complex obeys Beer's law over the zirconium concentration range 0.02-0.44 mug/ml and has a molar absorptivity of 1.54 x 10(5) 1.mole(-1). cm(-1) at 585 nm. The formation constant is log beta(3) = 16.15. Of 59 species studied, only EDTA, Ga, In, Ti, Hf and V(V) interfere seriously.     

Extraction-spectrophotometric determination of traces of copper(II), zinc(II), cadmium(II) and mercury(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

Summary Sensitive extraction-spectrophotometric procedures are described for the complexes of Cu(II), Zn(II), Cd(II) and Hg(II) with 5-Br-PADAP using chloroform as solvent. Optimal conditions have been established for the quantitative extraction of the metal chelates and their composition and optical characteristics have been determined as well. The conditional extraction constants amount logK _ex=10, the molar absorptivities of the complexes being 10⁵ l·mole^–1·cm^–1. Job's method and equilibrium shift method indicate the molar ratios M5-Br-PADAP=12.

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Spektralphotometrische Bestimmung von Spuren Cu(II), Zn(II), Cd(II) und Hg(II) mit 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)

Zusammenfassung Einfache und empfindliche Methoden zur extraktionsspektralphotometrischen Bestimmung von Spuren Cu(II), Zn(II), Cd(II) und Hg(II) mit 5-Br-PADAP wurden beschrieben. Chloroform wurde als Extraktionsmittel verwendet. Die optimalen Bedingungen für die quantitative Extraktion der Metallchelate wurden ermittelt und deren Zusammensetzung bestimmt. Die Stabilitätskonstanten haben hohe Werte (logK _ex=10), die molare Absorption der Komplexe beträgt 10⁵1·mol^–1·cm^–1. Das Molarverhältnis der Komplexe beträgt M5-Br-PADAP=12.

     

1.5th- and 2.5th-order derivative adsorption voltammetry of the cobalt(II)—2-(5′-bromo-2′-pyridylazo)-diethylaminophenol system

On the basis of the adsorptive characteristics of the cobalt(II) complex with 2-(5′-bromo-2′-pyridylazo)diethylaminophenol at a hanging mercury drop electrode in NH₃NH₄Cl, a more sensitive method for the determination of cobalt based on 1.5th- and 2.5th-order derivative adsorption voltammetry has been developed. The detection limit is one order of magnitude lower than that of normal linear-sweep adsorption voltammetry. The equations of the 1.5th- and 2.5th-order derivative of current with respect to time, peak potential and distance from peak to peak are discussed.     

Sensitive spectrophotometric determination of bismuth(III) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

The complex of the reagent 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) with Bi(III) has been studied. The composition and stability of this complex have been determined. An analytical method for the spectrophotometric determination of Bi(III) using its complex with 5-Br-PADAP has been developed. Variables influencing the method such as pH, wavelength, and time have been studied. The limitations of this method and the effect of interfering ions have been investigated. Comparison of this method with other methods cited in the literature for the determination of Bi(III) is also included.     

Spectrophotometric determination of gadolinium(III) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)

Reaction between gadolinium(III) and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5- Br-PADAP) was studied for delineating optimal conditions for complexation. This reagent can be used for the spectrophotometric determination of Gd(III) in concentrations ranging from 0.04 to 1.2 ppm (a = 1.76(+/- 0.03) x 10(5) (1.(-1) mole(-1). cm). The reaction takes place at a pH between 9.2 and 11.6. In the presence of Triton X-100 this complex is soluble in water. In order to overcome difficulties caused by the presence of other lanthanides, an ion exchange chromatographic technique was used.     

Atmospheric pressure chemical ionization mass spectrometric and visible spectrophotometric studies of copper(I) and copper(II) complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol.

Complexes of copper(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) formed in aqueous methanol in a wide range of pH (from acidic to alkaline) as well as copper(I)-5-Br-PADAP species formed in methanolic solutions were investigated by spectrophotometry and mass spectrometry. Pseudomolecular and fragment ions created in the atmospheric pressure chemical ionization (APCI) source confirmed the molecular masses of the complexes existing in the solvents and their structures. The structure of the Cu(II) complex with 5-Br-PADAP formed in acidic medium was proposed as CuR(R - H) (where R is the undissociated molecule of the reagent). The binding sites of the two bound reagent molecules were different: in one of them the oxygen atom of the dissociated phenolic group and the nitrogen atom from the azo (-N=N-) group took part in complex formation, whereas in the other only nitrogen atoms from the pyridyl ring and azo group were involved. The complex was stable and could not be reduced to Cu(I) species by use of standard reducing agents (ascorbic acid, hydroxylamine). In alkaline solutions the complex tended to polymerize and precipitated in media containing less than 80% of methanol. The copper(I)-5-Br-PADAP complex was extremely unstable and could be obtained (as a mixture with Cu(II) species) in media free of water or oxygen. For this complex, CuR(2) was proposed as the most probable structure. According to this proposal copper(I) reacted exclusively with nitrogen-containing binding sites and the undissociated phenolic group was not engaged in complex formation. In this system Cu(I)/Cu(II) electron transfer is very rapid, accelerated by a polar environment, e.g. in the presence of water molecules or dissolved oxygen.     

A study of the spectrophotometric determination of traces of cadmium(II) and copper(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the presence of polyglycol octylphenyl ether

A spectrophotometric study of the Cd(II) and Cu(II) complex of a new reagent, 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol (5-Br-PADAP) in the presence of polyglycol octylphenyl ether (OP) is presented. A reddish binary complex is formed at pH 9 and shows maximal absorbance at 560 nm with molar absorptivity of 1.16 × 10⁵ · mol⁻¹ · cm⁻¹ liter (Cd), 1.5 × 10⁵ mol⁻¹ · cm⁻¹ · liter (Cu). Beer's law is followed over the range 0.0 to 20 μg cadmium(II) and 0.0–18 μg copper(II). The continuous variation method and molar ratio method showed that the metal ligand ratio is 1:2; ordinarily, most ions do not interfere with the determination and the method can be applied for direct spectrophotometric determination of cadmium(II) and copper(II) in actual samples and the results obtained are satisfactory.     

Spectrophotometric determination of uranium(VI) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in a flow-injection system

The direct determination of uranium(VI) by a flow-injection procedure is based on spectrophotometric measurement with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the present of fluoride. The interfering effects of many commonly occuring elements were studied. The calibration curve was linear over the range 0.5–20 mg 1^?1 uranium(VI). The relative standard deviation obtained on a leach liquor containing 10 mg 1^?1 uranium(VI) was 1.9%. The procedure is rapid and convenient, and up to 40 samples can be analysed per hour.     

Extraction-spectrophotometric determination of traces of palladium by reaction between zinc(II) dibenzyldithiocarbamate and palladium(II)/2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

The simple and highly sensitive determination of palladium is based on the reaction between Pd(II)/5-Br-PADAP and Zn(II) DBDTC complexes in 1,2-dichloroethane or toluene at pH 9.7. At 530 nm, the molar absorptivity is about 0.8 × 10⁵ l mol ^?1 cm ^?1. Beer's law is obeyed in the concentration range 0.1–1.2 μg ml ^?1 Pd. Relative standard deviations are 2–5%. Metal ions reacting with either of the organic reagents interfere.     

2-(5-溴-2-吡啶偶氮)-5-二乙氨基酚与铕(Ⅲ)络合平衡的双系列线性回归法研究

2- ( 5 -溴 - 2 -吡啶偶氮 ) - 5 -二乙氨基酚 ( 5 - Br- PADAP)是一种灵敏的光度试剂 ,该试剂与铕 ( )的络合比及其稳定常数的研究尚未见报道。本文用双系列线性回归法研究了铕 ( )与 5 - Br- PADAP的络合反应 ,测得铕 ( )与 5 - Br- PADAP形成 1∶ 3的络合物 ,条件稳定常数 ( 1 gβn)为 1 6.5 2 ,最大吸收波长为60 5 nm,摩尔吸光系数为 4.67× 1 0 4 L· mol- 1· cm- 1。     

Spectrophotometric determination of trace uranium(VI) as a mixed ligand complex with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and aromatic carboxylic acid

Spectrophotometric studies on a uranium(VI) ternary complex and its analytical application are described. Uranium(VI) reacts with 5-Br-PADAP to form an unstable chelate, which precipitates on standing in 48% ethanolic aqueous solution. The colour stability of uranium(VI) complex is greatly improved by the presence of aromatic carboxylic acids. For the present purpose, o-hydroxybenzoic acid and its derivatives are best suited. The calibration graph is linear up to 2.6 g·ml^–1 of uranium(VI) at 578 nm. The role of carboxylic acid as an auxiliary ligand is discussed.     

Spectrophotometric procedure for the determination of uranium with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol at a nuclear reprocessing facility

A simple method for the determination of uranium in process- and waste-stream samples at a nuclear fuel reprocessing facility that can be applied entirely in a remote environment is described. The method is both sensitive and selective enough to be applicable for almost any uranium determination. Uranium in aqueous samples is extracted as a nitrate complex into 4-methylpentan-2-one (hexone) from an acid-deficient aluminium nitrate salting solution. An aliquot of the hexone extract is then mixed with a solution containing methanol, pyridine and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP). The absorbance of the U(VI)-Br- PADAP complex is measured at 580 nm. The detection limit for uranium is 0.8 μg with the linear range extending to 80 μg. Interference studies, modifications for organic samples and solid-containing samples and process laboratory data are presented.     

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.     

Simultaneous determination of Mn(II), Cu(II) and Fe(III) as 2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol complexes by adsorptive cathodic stripping voltammetry at a carbon paste electrode

A simple and precise square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV) method has been described for simultaneous determination of Mn(II), Cu(II) and Fe(III) in water samples using a carbon paste electrode. In 0.1 mol L⁻¹ acetate buffer (pH 5) containing 50 μmol L⁻¹ of 2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol (5-Br-PADAP), Mn(II), Cu(II) and Fe(III) were simultaneously determined as metal-complexes with 5-Br-PADAP following preconcentration onto the carbon paste electrode by adsorptive accumulation at +1.0 V (vs. Ag/AgCl/3 M KCl). Insignificant interference from various cations (K⁺, Na⁺, Mg²⁺, Ca²⁺, Al³⁺, Bi³⁺, Sb³⁺, Se⁴⁺, Zn²⁺, Ni²⁺, Co²⁺, Cd²⁺, Pb²⁺, V⁵⁺, Ti⁴⁺ and NH₄⁺), anions (HCO₃⁻, Cl⁻, NO³⁻, SO₄²⁻ and PO₄³⁻) and ascorbic acid was noticed. Limits of detection of 0.066, 0.108 and 0.093 μg L⁻¹ and limits of quantitation of 0.22, 0.36 and 0.31 μg L⁻¹ Mn(II), Cu(II) and Fe(III), respectively, were achieved by the described method. The described stripping voltammetry method was successfully applied for simultaneous determination of Mn(II), Cu(II) and Fe(III) in ground, tap and bottled natural water samples.     

Structural isomers in a 2-(5-bromo-2-pyridylazo)-5diethylaminophenolatochloropalladium(II) crystal.

Crystal structure of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenolatochloropalladium(II) (PdLCl) has been determined by X-ray diffraction. A crystal of PdLCl was constructed by two structural isomers of PdLCl molecules, which were particularly different in the positions of the carbon atoms at the diethylamino group, having cis-like or trans-like conformation for the carbon atoms. The molecules of PdLCl in the crystal were warped by a steric hindrance of the diethylamino group.