Spectrophotometric determination of vanadium in steel and alloys with 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol

Using spectrophotometric methods, the protopysis constant of the 5.ClDMPAP reagent (pK_a1 = −0.19; pK_a2 = 1.97; pK_a3 = 11.98) and the stability constant of its vanadic complex (6.0 ± 0.11) × 10¹⁴ were determined. A high-sensitivity spectrophotometric method was developed to determine V(V) using 0.1–1.2 ppm and pH = 3.8. ε₅₈₆ = 55,300 ± 400 liters · mol⁻¹ · cm⁻¹. A study on the most important interferences and the way to eliminate them was carried out. The method can be applied to the determination of the element in steels and ferrovanadiums.     

Complexometric titration of Ti(IV) with 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol as indicator

A method for determination of titanium by a reverse titration with EDTA in the presence of hydrogen peroxide, with 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol as indicator, is presented; use of the method for analysis of titanium paints is also described.     

Sensitive spectrophotometric determination of vanadium with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol after extraction with N-benzoyl-N-phenylhydroxylamine

A selective and precise spectrophotometric determination of vanadium(V) is performed after preceding extraction with N-benzoyl-N-phenylhydroxylamine (BPHA). The color is developed in a water-ethanol solution with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol (5-Cl-DMPAP). The molar absorptivity at 588 nm is (6.57 ± 0.05) × 10⁴ L mol^–1 cm^–1 at pH 2.1. The method permits the determination of vanadium (V) at trace levels in the presence of large amounts of other ions. It is applied to the determination of vanadium in aluminium (analytical reagent grade) and in human hair. High accuracy and precision is obtained. Received: 18 April 1997 / Revised: 20 June 1997 / Accepted: 25 June 1997     

Sensitive spectrophotometric determination of vanadium with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol after extraction with N-benzoyl-N-phenylhydroxylamine

A selective and precise spectrophotometric determination of vanadium(V) is performed after preceding extraction with N-benzoyl-N-phenylhydroxylamine (BPHA). The color is developed in a water-ethanol solution with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol (5-Cl-DMPAP). The molar absorptivity at 588 nm is (6.57 ± 0.05) × 10⁴ L mol^–1 cm^–1 at pH 2.1. The method permits the determination of vanadium (V) at trace levels in the presence of large amounts of other ions. It is applied to the determination of vanadium in aluminium (analytical reagent grade) and in human hair. High accuracy and precision is obtained.     

Extraction and sensitive spectrophotometric determination of ytterbium with 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminophenol

The operating conditions for the absorptiometric determination of Yb(III) with the reagent 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminophenol (3,5-diClDMPAP) by a liquid—liquid extraction technique are presented. The complex yields a molar absorptivity of 1.54 × 10⁵l.mole⁻¹.cm⁻¹ (λ_max = 588 nm) and an optimum concentration range of 0.025–1.360n mg/l., at pH = 10. The method developed has been applied to the determination of Yb(III) in synthetic and concrete mixtures.     

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.     

5-(5-氯-2-吡啶偶氮)-2,4-二氨基甲苯分光光度法测定微量钌(Ⅲ)

研究了 5- ( 5-氯 - 2 -吡啶偶氮 ) - 2 .4-二氨基甲苯 ( 5- Cl- PADAT)与钌 ( )的显色反应。在 p H4.0～ 6.5HAc- Na Ac缓冲溶液中 ,在加热的条件下 ,5- Cl-PADAT与 Ru( )形成稳定的配合物 ,加入无机酸 ( HCl,HCl O4 ,H2 SO4 ,H3 PO4 )酸化后 ,其最大吸收波长位于 50 5nm处 ,表观摩尔吸光系数为 8.5×1 0 4 L· mol-1· cm-1,钌浓度在 0～ 6μg/ 1 0 m L范围内服从比耳定律 ,Ru( )与 5- Cl- PADAT配合物的摩尔比为 1∶ 2。以 EDTA为掩蔽剂 ,方法具有良好的选择性 ,已应用于合成样中钌的测定。     

Spectrophotometric determination of cadmium with 1-[(5-chloro-2-pyridyl)azo]-2-naphthol

Summary Cadmium(II) reacts with l-[(5-chloro-2-pyridyl)azo]-2-naphthol (5-C1--PAN) in aqueous solution; the complex can be extracted with chloroform at pH 9–11 to give a red solution with an absorption peak at 566 nm. The colour in chloroform is stable and the system conforms to Beer's law; optimal range in the chloroform layer for measurement at 1.00-cm cells is 0.1–1 ppm cadmium. Common cations and anions do not interfere. Large amounts of some cations can be masked by potassium cyanide, the cadmium cyanide complex being demasked by formaldehyde. The proposed method is one of the most sensitive procedure for the determination of cadmium. The molar absorptivity in the chloroform extract is 6.6· 10⁴ 1 mole^–1 cm^–2 at 566 nm.

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Zusammenfassung Cadmium reagiert mit 1-(5-Chlor-2-pyridyl) azo-2-naphthol, 5-C1--PAN, in wäßriger Lösung; der rote Komplex kann bei pH 9–11 mit Chloroform extrahiert werden und hat ein Absorptionsmaximum bei 566 nm. Die chloroformische Lösung ist stabil und entspricht dem Beerschen Gesetz; für die Messung in l-cm-Küvetten eignen sich am besten 0,1–1 ppm Cd. Übliche Ionen stören nicht. Große Mengen einiger Kationen können mit KCN maskiert werden, wahrend [Cd(CN)₄]^2– von Formaldehyd gespalten wird. Die vorgeschlagene Methode ist eine der empfindlichsten für die Bestimmung von Cd. Die molare Extinktion des chloroformischen Extraktes betragt bei 566 nm 6,6 · 10⁴ 1 · mol^–1 · cm^–2.

     

Synthesis of 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminophenol and its application to the spectrophotometric determination of cobalt

2-(3,5-Dichloro-2-pyridylazo)-5-dimethylaminophenol (3,5-diCl-DMPAP) has been synthesized and its analytical application investigated. It reacts with cobalt in aqueous solution at pH 2.2-6.0 and room temperature to form a water-soluble ML(2) complex with absorption maximum at 590 nm, and molar absorptivity 8.4 x 10(4) l.mole(-1).cm(-1). Interference from other transition metals can be eliminated by their solvent extraction with 8-hydroxyquinoline. The method has been successfully applied to determination of cobalt in mild steels.     

Synthesis and characterization of 2-(3,5-Dichloro-2-pyridylazo)-5-dimethylaminophenol as a reagent for determination of lanthanum

2-(3,5-Dichloro-2-pyridylazo)-5-dimethylaminophenol (3,5-diCIDMPAP) has been synthesized and its spectral properties, acid-base equilibria, physical constants, and solubility and stability are presented. This reagent is highly promising for the determination of lanthanides. The influence of Triton X-100 on the dissociation constant has been investigated and the association constant between the reagent and the surfactant determined. Analytical data for the 3,5-diCIDMPAP complexes with La(III), Eu(III), Gd(III), Er(III) and Yb(III) are given, La(III) in synthetic samples has been determined with 3,5-diCIDMPAP.     

Spectrophotometric determination of uranium with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol (PAN) rcacts with uranium to form a deep red precipitate in ammoniacal solutions, this can be extracted with chloroform if sodium chloride or sulfate is added and it has a maximum absorption at 560 mμ The color is stable and follows Beer's law. Trace amounts of uranium may be determined in the presence of many metals without prior separation if strong complexing agents, such) as EDTA or cyanide, are added     

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.     

Colorimetric determination of zirconium with 1-(2-pyridylazo)-2-naphthol

A method is described for the determination of as little as 50 ppm of zirconium in uranium-fission element alloys and zinc magnesium-uranium-fission element alloys. Zirconium is extracted from a nitric acid-aluminium nitrate medium with dibutyl phosphate in toluene. The uranium co-extracted with the zirconium is removed by scrubbing with hydrochloric acid-ammonium thiocyanate solution. A portion of the organic phase is mixed with pyridine-toluene solution of 1-(2-pyridylazo)-2-naphthol to develop the colour.     

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.     

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.     

Influence of salts on the extraction-spectrophotometric determination of zinc and cadmium with 1-(2-pyridylazo)-2-naphthol

Summary The influence of NaClO₄, Na₂SO₄, NaCl, KBr, KI and KSCN on the extraction-spectrophotometric determination of zinc and cadmium with PAN reagent has been investigated. In the concentration range below 0.3 mole/l all the examined salts caused an increase of absorbance of the chloroform Zn-PAN and Cd-PAN extracts. This effect is due to an increased percentage of extraction of both metals. Higher concentrations of the salts (above 0.3 mole/l) did not influence the zinc determination. In case of cadmium the salts with complexing ions (NaCl, KBr, KI and KSCN) caused a decrease of absorbance. An undesirable influence of ethanol on the extraction of Zn and Cd has also been noted.

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Einflu\ von Salzen auf die extraktions-spektralphotometrische Bestimmung von Zink und Cadmium mit 1-(2-Pyridylazo)-2-naphthol

Zusammenfassung Der Einflu\ von NaClO₄, Na₂SO₄, NaCl, KBr, KI und KSCN wurde untersucht. Im Konzentrationsbereich unter 0,3 Mol/l verursachen alle geprüften Salze eine Extinktionserhöhung der Chloroformextrakte von Zn-PAN und Cd-PAN, da beide Metalle verstÄrkt extrahiert werden. Durch höhere Salzkonzentration (> 0,3 Mol/l) wird die Zinkbestimmung nicht beeinflu\t. Bei Cadmium verursachen Salze mit komplexierenden Ionen (NaCl, KBr, KI, KSCN) eine Extinktionsabnahme. Ein nachteiliger Einflu\ von Ethanol auf die Extraktion von Cd und Zn wurde ebenfalls festgestellt.

     

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.