1-[(5-Chloro-2-Pyridyl)Azo]-2-Naphthol as a new extraction- photometric reagent for metals

The heterocyclic azo compound, 1-[(5-chloro-2-pyridyl)azo]-2-naphthol (5-Cl-β-PAN), forms various coloured metal chelates, which can be extracted with different organic solvents. Chelate stability is greatly affected by pH. The molar absorptivities are usually considerably greater than those of the β-PAN chelate. Although the bathochromic shifts produced on chelation are no greater than those with 5-Br-β-PAN, the selectivity is increased. The reactivity of tri- and tetravalent metal ions is decreased appreciably by introduction of the chlorine. A correct choice of pH, solvent and masking reagent allows 5-C1-β-PAN to be made reasonably selective.     

Liquid–liquid extraction of copper(II) with substituted salicylideneanilines from sulfate media

The liquid–liquid extraction of copper(II) with Schiff bases in chloroform from sulfate media is studied for pH and concentration of the extractant. Stoichiometry coefficients of the extracted species are determined by the slope analysis method. With salicylideneaniline, the copper(II) is extracted as a mixed chelate complex, CuL₂HL. In the presence of substituent, the copper is extracted as simple chelates, CuL₂. The trends in the values of extraction constants were explained in terms of the nature of the substituents.     

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.

     

Extraction-spectrophotometric determination of trace iron (II) in sea water with 2-[2-(3,5-dibromopyridyl)azo]-5-diethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of iron(II) with 2-[2-(3,5-dibromopyridyl)azo]-5-diethyl-aminobenzoic acid. The reagent forms a stable and blue 12 iron/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the iron(II) complex is 1.09 × 10⁵ 1 mol^–1 cm^–1 at 624 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper, nickel and vanadium can be removed by using dimethylglyoxime and EDTA. The method is applied to the determination of iron (II) in sea water and aluminium alloys with good precision and accuracy.     

Extraction and spectrophotometric determination of lead(II) with pyridine-2-acetaldehyde salicyloylhydrazone

Lead(II) reacts with pyridine-2-acetaldehyde salicyloylhydrazone (PASH) in the pH range 8.6-9.3 to form a yellow-green, 1:2 chelate which can be extracted into chloroform. Beer's law is obeyed in the concentration range 1.5-6.2 mug ml(-1) of lead(II). The molar absorptivity of the extracted species is 1.93 x 10(4) l mol(-1) cm(-1) at 380 nm. The proposed method is sensitive, simple, rapid, accurate and has been satisfactorily applied for the determination of lead in synthetic mixtures, alloys, water and soil samples.     

Extraction and spectrophotometric determination of zinc in coal fly ash and pond sediments with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of zinc with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid. The reagent forms a stable, blue 1:2 zinc/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the zinc(II) complex is 1.26 × 10⁵ l mol^?1 cm^?1 at 610 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper and nickel can be masked with dimethylglyoxime and aluminium and iron with a mixture of sodium fluoride and triethanolamine. The method is applied to the determination of zinc in coal fly ash and pond sediments with good precision and accuracy.     

Spectrophotometric determination of uranium with 1-[(5-Methyl-2-pyridyl)azo]-2-naphthol

Summary Uranium(VI) reacts with 1-[(5-methyl-2-pyridyl)azo]-2-naphthol (5-Me--PAN) in aqueous solution. The complex can be extracted with chloroform at pH 7.0–11.5 to give a red solution with an absorbance peak at 560 nm. The color is stable and the system conforms to Beer's law at the range of 1.5–8 ppm uranium in chloroform layer. Common anions and cations do not interfere. Large amounts of interfering cations can be masked by potassium cyanide, EDTA or triethanolamine. The proposed method is a selective procedure for the determination of uranium. The molar absorptivity in the chloroform extract is 2.1×10⁴ l mole^–1 cm^–1 at 560 nm.

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Zusammenfassung Uran(VI) reagiert mit 1-[(5-Methyl-2-pyridyl)azo]-2-naphthol(5-Me--PAN) in wäßriger Lösung unter Bildung einer mit Chloroform bei pH 7,0–11,5 extrahierbaren, roten Komplexverbindung mit einem Absorptionsmaximum bei 560 nm. Die Färbung ist beständig und folgt dem Beerschen Gesetz zwischen 1,5 und 8 ppm Uran. Die üblichen Ionen stören nicht. Große Mengen störender Kationen können mit Kaliumcyanid, ÄDTA oder Triäthanolamin maskiert werden. Die vorgeschlagene Methode ist für die Uranbestimmung selektiv. Die molare Extinktion des Chloroformextraktes beträgt 2,1×10⁴ l·Mol·^–1 cm^–1 bei 560 nm.

     

A new tetrahedrally distorted copper(II) complex derived from disulphide coupled N-(2-ethanethiol)salicylideneimine

Copper(II) acetate reacts with N-(2-ethanethiol)salicylideneimine forming an ONNO chelate of α,α′-(diethylenedisulphide)-N,N′-disalicylideneimine with an uncoordinated disulphide. This copper(II) complex can also be obtained in higher yield if the thiol is first oxidized to disulphide with iodine. The geometry about copper(II) is distorted from planar to a flattened tetrahedron.     

2-(8-quinolylazo)-4,5-diphenylimidazole — a sensitive extraction spectrophotometric reagent for mercury

Mercury(II) reacts with 2-(8-quinolylazo)-4,5-diphenylimidazole in aqueous solution; the complex can be extracted with chloroform or 1,2-dichloroethane at pH 4.5–9.5 to give a stable reddish-purple solution. The system conforms to Beer's law; the optimal range in chloroform is 0.05–2 ppm mercury (1-cm cells). Of 25 metal ions investigated, only copper and vanadium interfere seriously. The proposed method is exceptionally sensitive; the molar absorptivity in the chloroform extract is 7.3 × 10⁴ l mol^?1 cm^?1 at 580 nm; the Sandell sensitivity is 0.0027μg Hg cm^?2.     

Preconcentration of copper by cloud point extraction with 1-(2-pyridylazo)-2-naphthol and determination by neutron activation

A method for the preconcentration of Cu(II) by cloud point extraction (CPE) followed by its determination using neutron activation analysis (NAA) was developed. The method involves the use of a nonionic surfactant, namely PONPE-7.5, and a chelating agent 1-(2-pyridylazo)-2-naphthol (PAN). The phase diagram of the surfactant was constructed and the effects of different additives on the cloud point were investigated. Factors, such as the solution pH, ionic strength, temperature, and concentrations of chelating agent and surfactant, which can influence the extraction efficiency of the metal, were optimized. The copper(II) chelate was extracted into a surfactant-rich phase of small volume with a recovery of nearly 100% and a preconcentration factor of 60. The small volume of the surfactant-rich phase obtained complies with the green chemistry concept, allowing the design of extraction procedures having lower toxicity than those using organic solvents. The method was applied to tap water samples.     

Synthesis and spectrophotometric study of 2-[2-(3,5-dibromopyridyl,)azo] -5-dimethylaminobenzoic acid as an analytical reagent: Determination of nickel

2-[2-(3,5-Dibrornopyridyl)azo]-5-dimethyIam;nobenzoic acid (3,5-diBr-PAMB) has been synthesized and its potential for the spectrophotometric determination of metals studied. It reacts sensitively with nickel, cobalt, iron and copper, and is particularly useful for nickel. The apparent molar absorptivity in chloroform is 1.50 × 10⁵ l mol^-1 cm^-1 and the Sandell sensitivity is 0.4 ng Ni cm^-2. Nickel reacts with 3.5-diBr-PAMB at pH 4–10; at pH 4–7 the complex can be extracted into chloroform to give a stable purple solution. The optimal calibration range is 0.04–0.4 ppm Ni. Only Cu, Co, Fe, Pd and V interfere seriously but Pd, Cu and V can be masked by thiourea.     

Solvent extraction of copper(II) from sulfate medium with N -(2-hydroxybenzylidene)aniline

Solvent extraction of copper(II) from sulfate medium with N-(2-hydroxybenzylidene)aniline is studied with the following parameters: pH, concentration of the extractant, nature of diluent, and temperature. The extraction of copper(II) proceeds by a cation exchange mechanism and the extracted species are CuL₂ in cyclohexane and toluene and CuL₂ with some CuL₂HL in chloroform. The equilibrium constants have been calculated as well as thermodynamic parameters ΔH°, ΔS°, and ΔG°. The temperature effect on the solvent extraction of copper(II) with N-(2-hydroxybenzylidene)aniline in cyclohexane is discussed.     

Spectrophotometric determination of palladium with glyoxime and chloroform extraction

Palladium(II) reacts with glyoxime in a 1:2 mole ratio to form a yellow water-insoluble chelate, which is soluble in chloroform; the solution has an absorption maximum at 397 mμ. Absorbance measurements at 397 mμ allow determination of the palladium glyoximate in solution. The maximum amount of palladium is extracted at pH 1.0. Platinum(II), iridium(III), gold(III), and phosphate cause some positive interference, and iron(II, III) causes negative interference; the interferences can be eliminated by masking with EDTA. The species extracted has been shown to be identical with that used to prepare the original palladium glyoximate chloroform solution. With EDTA and multiple extractions, the method is satisfactory for the determination of palladium in the presence of other platinum-group elements and many other cations.     

2-[2-(5-Bromopyridyl)azo]-5-dimethylaminophenol; a new sensitive reagent for cadmium

Cadmium(II) reacts with 2-[2-(5-bromopyridyl)azo]-5-dimethyl-aminophenol (5-Br-DMPAP) in aqueous solution; the complex can be extracted with organic solvents such as chloroform, 3-methyl-l-butanol and methyl isobutyl ketone at pH 8–10.5 to give a red solution which absorbs at 525–555 nm. The absorbance in organic solvents is stable and the system conforms to Beer's law; the optimal range in 3-methyl-1-butanol for measurement in 1.00-cm cells is 0.01–l p.p.m. cadmium. Moderate amounts of many cations and anions do not interfere, and interfering cations such as zinc, copper, manganese and nickel can be separated by extraction with dithizone. The 5-Br-DMPAP method is one of the most sensitive procedures available for the determination of cadmium; the molar absorptivity in a 3-methyl-1-butanol extract is 1.41·10⁵ 1 mol^?1 cm^?1 at 555 nm.     

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.     

Effects of auxiliary complex-forming agents on the rate of metallochromic indicator colour change--II: mechanism of the colour change of pan in copper-EDTA titrations

The rate of the ligand substitution reaction of copper (II)-PAN (CuR) with EDTA (Y) has been determined spectrophotometrically in 5% v/v dioxan over the pH range 5.0-6.3 at mu = 0.1 (NaClO(4)) and at 25 degrees . In the absence of 1,10-phenanthroline the rate law is expressed as -d[CuR(+)]/dt = 10(3.2) [CuR(+) [Y'], and the release of PAN from the reaction intermediate CuRY is the rate-determining step. In the presence of 1,10-phenanthroline (X), however, copper forms a stable mixed-ligand complex (CuRX(+)), and the rate of substitution with EDTA is expressed as -d[CuRX(+)]/dt = (10(6.2)[H(+)] + 10(4.8)[X]) [CuRX(+). The release of PAN from the mixed-ligand complex by H(+) and X is possibly the rate-determining step, with the copper-phenanthroline complexes produced undergoing fast exchange with EDTA. The stability constant of CuRX(+) has been determined spectrophotometrically in 5% v/v dioxan at mu = 0.1, and at 25 degrees as [CuRX(+)]/[Cu(2+)] [R(-)] [X] = 10(21.2). The acceleration of the rate of substitution of copper (II)-PAN chelate may be explained by the fact that the Cu-PAN bond in the distorted octahedral mixed-ligand complex CuRX is weaker than in the reaction intermediate CuRY.     

Extraction of copper(II) with the APCD/DIBK system from concentrated hydrochloric and nitric acid media: estimation of true limit of acidity for the extraction

The extraction of copper(II) from strongly acidic solution (0.01-8M hydrochloric and 0.01-5M nitric acid) with ammonium 1-pyrrolidinecarbodithioate in di-isobutyl ketone has been studied. Compared with the hydrochloric acid system, a considerably larger amount of the reagent is needed for complete extraction of copper chelate from nitric acid solution as the extract is more unstable in the nitric acid system. The decomposition of copper chelates extracted from nitric acid is based on the oxidation of the reagent and the chelate; the spectral change of the extract from nitric acid suggests that the copper(II) chelate is initially oxidized to copper(II) and then decomposes. The upper limit of the acidity of both acids from which the copper chelate can be quantitatively extracted strongly depends on the reagent concentration; the limit with 8 x 10(-2)M APCD (500-fold reagent: metal molar ratio) was taken as 8 and 4M for hydrochloric and nitric acid, respectively.     

Rapid extraction of copper(II) with 2-thenoyltrifluoroacetone direct colorimetric determination in the organic phase

Summary The chelating agent, 2-thenoyltrifluoroacetone has been employed for rapid extraction and colorimetric determination of milligram amounts of copper(II) in one operation. At pH 2.4–6.0 copper(II) is extracted quantitatively from an aqueous solution by TTA-benzene in a single extraction. The green-coloured copper(II)-TTA chelate solution in benzene obeysBeer's law at 430 m over the range of 16–180g copper per millilitre. The coloured system is stable for 143 hours. It can tolerate silver, mercury(II), bismuth (<5 mg) and small amounts (<100 mg) of citrate and tartrate, whereas cobalt(II), nickel(II), iron(III), aluminium(III), cerium(IV), thorium and zirconium seriously interfere. The proposed method is reproducible to within ±1.4%.     

A spectrophotometric method for the determination of anionic surfactants at μg l-1 levels

The anionic surfactant is extracted into chloroform as a neutral complex with the bis(ethylenediamine)copper(II) cation, and copper(II) is determined spectrophotometrically after addition of 1-(2-pyridylazo)-2-naphthol and diethylamine. With a 200-ml water sample, the limit of detection is 5 μg l^-1 (as linear alkyl sulphonic acids). The method is simple and is directly applicable to fresh, estuarine and marine waters.     

Spectrophotometric determination of yttrium in aluminium base alloys with 1-[(5-Methyl-2-pyridyl)azo]-2-naphthol

Summary A highly sensitive and selective Spectrophotometric method has been developed for the determination of yttrium in aluminium base alloys. The method is based on the red water-insoluble complex formed when yttrium and 1-[(5-methyl-2-pyridyl)azo]-2-naphthol (5-Me--PAN) react in a pH 9.5–11.2 solution. This complex could be extracted into ether (absorption maximum, 530 nm). Beer's law is obeyed up to 1 p. p. m. of yttrium and the molar absorptivity is 6.4 · 10⁴ l · mole^–1 · cm^–1 at 530 nm.

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Zusammenfassung Eine hochempfindliche und selektive spektrophotometrische Methode zur Bestimmung von Yttrium in Aluminiumlegierungen wurde ausgearbeitet. Sie beruht auf der Bildung der roten, wasserlöslichen Komplexverbindung des Yttriums mit 1-[(5-Methyl-2-pyridyl)azo]-2-naphthol(5-Me--PAN) bei pH 9,5–11,2. Diese Verbindung läßt sich mit Äther extrahieren und hat ein Absorptionsmaximum bei 530 nm. Das Beersche Gesetz ist bis zu 1 ppm Yttrium erfüllt. Die molare Extinktion beträgt 6,4 · 10⁴ 1 · Mol^–1 cm^–1 bei 530 nm.