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.     

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.     

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.     

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.     

Simultaneous determination of gallium and indium with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in cationic micellar medium using derivative spectrophotometry.

A new derivative spectrophotometric method for rapid and selective trace analysis of Ga3+ and In3+ and for their simultaneous determination using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in a cationic micellar medium is reported. Molar absorptivity and Sandell's sensitivity of 1:1 Ga+ and In3+ complexes at their lambda(max) 553 nm and 558 nm are: 7.22 x 10(4) l mol(-1) cm(-1) and 5.85 x 10(4) l mol(-1) cm(-1), and 0.96 ng cm(-2) and 1.96 ng cm(-2), respectively. Linearity is observed in the concentration range 0.023-0.700 microg ml(-1) for gallium and 0.076-1.52 microg ml(-1) for indium; IUPAC detection limit is 0.012 and 0.035 ng ml(-1), respectively. These metal ions interfere with the determination of each other. However, 0.07-0.70 microg ml(-1) Ga3+ and 0.115-1.150 microg ml(-1) In3+ could be determined simultaneously when present together by the derivative method without any prior separation. The proposed procedures have been successfully applied for the individual and simultaneous determination of gallium and indium in synthetic binary mixtures, standard reference materials and environmental samples.     

Second derivative spectrophotometric method for simultaneous determination of cobalt, nickel and iron using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

A simple, sensitive and rapid derivative spectrophotometric method using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) has been developed for simultaneous determination of Co(II), Ni(II) and Fe(II) which have very similar chemical behavior and appear together in many real samples. The complexes of all these metal ions with 5-Br-PADAP were formed immediately at pH 7.0 ammonium acetate buffered solution and were stable for at least 24 h. Second derivative spectra were selected for evaluation, because working wavelength determination was more precise and spectral overlap was less than in the ordinary and first derivative spectra. Three wavelengths at which the complexes exhibit extremum ²D values for Co(II), Ni(II) and Fe(II) were selected as analytical wavelengths, i.e., 640, 600 and 740 nm, respectively. Calibration curves drawn with zero-to-peak values at mentioned wavelengths were linear between 80 and 2000 ng ml⁻¹ for each metal ion. Concentrations of Co(II) and Ni(II) were calculated from the total ²D values and the sum of the linear equations for these three cations at 640 and 600 nm, after Fe(II) assay by making use of the ²D value at 740 nm. Limits of detection (LOD) for Co(II), Ni(II) and Fe(II) were 2.7, 13.9 and 3.0 ng ml⁻¹, respectively. The method has been applied to tool steel and heater resistance wire samples successfully.     

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.     

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.     

Selective spectrophotometric determination of thorium(IV) with 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol

A spectrophotometric study of the Th(IV) complex of a new reagent 2-(5-Bromo-2- pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is presented. A reddish brown complex is formed at pH 4.86, and shows maximal absorbance at 580 nm with molar absorptivity of 1.66 × 10⁵ mol⁻¹ cm⁻¹ liter. Beer's law is obeyed over the range 0.0 to 15 μg of thorium. Rare earths ions like La³⁺, Ce³⁺, and Y³⁺ do not interfere because they form complexes with 5-Br-PADAP at higher pH's (>9.94) (1). A new method for determining trace amounts of thorium is proposed, which possesses the advantages of high sensitivity and selectivity.     

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.     

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

A sensitive spectrophotometric method for zinc has been established by reacting zinc with 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol (3,5-diBr-PADAP) in the presence of an anionic surfactant, sodium lauryl sulphate. The molar absorptivity is 1.3 x 10(5) l.mole(-1).cm(-1) at 570 nm. The molar ratio of zinc to 3,5-diBr-PADAP is 1:2. Beer's law is obeyed up to 0.7 ppm of zinc. With preseparation of zinc by extraction of its thiocyanate complex, the method has been applied to the determination of zinc in waste water.     

Sensitive spectrophotometric determination of ascorbic acid in fruit juices and pharmaceutical formulations using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP)

A simple and very sensitive method has been developed for the determination of ascorbic acid based on the oxidation of ascorbic acid to dehydroascorbic acid by iron(III), followed by a complexation of iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(Br-PADAP). The iron(II) complex is formed immediately, with absorption maxima at 560 and 748 nm and a molar absorptivity of 1.31 × 10⁵ l mole^–1cm^–1 and 5.69 × 10⁴ l mole^–1cm^–1, respectively. The ascorbic acid determination is possible with a linear range up to 2.4 μg ml^–1, a calibration sensitivity of 0.744 ml μg^–1 at 560 nm and 0.323 ml μg^–1 at 748 nm, and a detection limit of 15 ng ml^–1 and 44 ng ml^–1, respectively. The procedure was used for the ascorbic acid determination in several fruit juices and pharmaceutical formulations. The results demonstrated a good precision (R.S.D. < 1%) and are in agreement with those obtained with others methods. The Br-PADAP method proposed is six times more sensitive than the method using the iron(II)-1,10-phenanthroline system. Received: 7 May 1996 / Revised: 1 July 1996 / Accepted: 8 August 1996     

Sensitive spectrophotometric determination of ascorbic acid in fruit juices and pharmaceutical formulations using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP)

A simple and very sensitive method has been developed for the determination of ascorbic acid based on the oxidation of ascorbic acid to dehydroascorbic acid by iron(III), followed by a complexation of iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(Br-PADAP). The iron(II) complex is formed immediately, with absorption maxima at 560 and 748 nm and a molar absorptivity of 1.31 × 10⁵ l mole^–1cm^–1 and 5.69 × 10⁴ l mole^–1cm^–1, respectively. The ascorbic acid determination is possible with a linear range up to 2.4 μg ml^–1, a calibration sensitivity of 0.744 ml μg^–1 at 560 nm and 0.323 ml μg^–1 at 748 nm, and a detection limit of 15 ng ml^–1 and 44 ng ml^–1, respectively. The procedure was used for the ascorbic acid determination in several fruit juices and pharmaceutical formulations. The results demonstrated a good precision (R.S.D. < 1%) and are in agreement with those obtained with others methods. The Br-PADAP method proposed is six times more sensitive than the method using the iron(II)-1,10-phenanthroline system. Received: 7 May 1996 / Revised: 1 July 1996 / Accepted: 8 August 1996     

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.

     

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.     

Sensitive spectrophotometric determination of vanadium with 2-(5-bromo-2-pyridylazo)-5-diethyl-aminophenol (5-Br-PADAP)

A new sensitive and highly selective method is described for the spectrophotometric determination of microgram amounts of vanadium(V). First, vanadium is isolated by extraction withN-benzoyl-N-phenylhydroxylamine (BPHA) in chloroform from about 4M hydrochloric acid medium. Then, chloroform is evaporated and the residue mineralized with mixture of cone. perchloric and nitric acid. Finally, a colour reaction of vanadium(V) separated with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) in an acetate buffer (pH 4.5) gives a molar absorptivity of 5.48×10⁴l·mol^–1·cm^–1 at 585 nm. The proposed method was applied for the determination of traces of vanadium in aluminium samples. The results obtained show a good precision and accuracy of the method.     

Silaned glass beads for the preconcentration and spectrophotometric determination of cobalt with 2-(2-pyridylazo)-5-diethylaminophenol

Silaned glass beads are applied for the preconcentration and spectrophotometric determination of cobalt with 2-(2-pyridylazo)-5-diethylaminophenol (PADAP). Traces of cobalt are collected as the coloured PADAP complex on a column of the beads, and the complex is then eluted with a small volume of ethanol-hydrochloric acid mixture and the absorbance of the eluate is measured at 575 nm. The cobalt can easily be concentrated by a factor of 50-500 in this way, and 0.1-2 mug of cobalt in 100 ml of sample solution can be determined reproducibly. High concentrations of Fe(III), Cr(III), Pb, Zn, Cu(II), Mn(II), Cd, Al, Ca and Mg can be tolerated but Pd(II) interferes.     

Adsorption voltammetry of the copper(II) 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complex

The voltammetric determination of copper(II), based on adsorptive accumulation of the Cu(II)-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (S-Br-PADAP) complex on a hanging mercury drop electrode, is reported. The complex can be accumulated at the electrode at constant potential in 0.1M ammonium nitrate/ammonia buffer solution, and its reduction wave observed by scanning the potential in the negative direction, in the differential pulse mode. The calibration graph for copper is linear over the range 0.05-0.5muM, with accumulation for 5 min at -0.20 V. The adsorption of the complex is discussed and compared with that of copper complexes with several other pyridylazo derivatives.