Spectrophotometric determination of nickel with 1-(1,2,4-triazolyl-3-azo)-2-naphthol with application to steel

Nickel(II) reacts with 1-(1,2,4-triazolyl-3-azo)-2-naphthol (TRAN) in aqueous 40% ethanol at pH 5 to form a red 1:2 complex having an absorption peak at 523 nm. The system conforms to Beer's Law in the range 0.2–2.8 ppm Ni(II). The molar absorptivity is 3.7 × 10⁴ l mol^-1 cm^-1. Various interferences can be avoided by extraction of the Ni(II)—TRAN complex into chloroform, which allows determinations of nickel in steels.     

Syntheses and spectrophotometric studies of 2-(2-thiazolylazo)- and 2-(2-benzothiazolylazo)-5-dimethylaminobenzoic acids as analytical reagents: Determination of nickel

2-(2-ThiazolyIazo)-5-dimethylaminobenzoic acid (TAMB) and 2-(2-benzothiazolylazo)-5-dimethylaminobenzoic acid (BTAMB) have been synthesized, and their potential for determinations of metals has been studied spectrophotometrically. Both are extremely sensitive chromogenic reagents for the determination of nickel. Molar absorptivities in aqueous methanol are 0.95 × 10⁵ (TAMB) and 1.2 × 10⁵ (BTAMB). In aqueous methanol, at apparent pH 5–9.5, the system conforms to Beer's law for 0.05–0.5 ppm nickel; Cu, Cr, Co, Pd and Fe interfere, but they can easily be masked.     

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.     

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.     

Reversed-phase ion-pair partition liquid chromatography of chelates with 2-(3,5-dibromo-2-pyridylazo)-5-[N-ethyl-N-(3-sulphopropyl) amino] phenol and analogues

The ion-pair reversed-phase chromatography of some transition metal chelates with 2-(3,5-dibromo-2-pyridylazo)-5-[N-ethyl-N-(3-sulphopropyl)amino]phenol (3,5-diBr-PAESPAP) was studied. 3,5-DiBr-PAESPAP and its V(V), Cr(III), Fe(II), Co(III) and Ni(II) chelates were retained on and the copper (II), zinc(II) and cadmium(II) chelates dissociated in an ODS column using acetonitrile/water (37+63, v/v) (pH 7.0) containing 0.01 M acetate, 0.01 M 3-(N-morpholino)propanesulphonate buffer (pH 7.0) and 0.05 M Na⁺ as mobile phase. The chromatograms of 3,5-diBr-PAESPAP chelates were compared with those of the chelates with 2-(3,5-dibromo- 2-pyridylazo)-5-[N-(3-sulphopropyl)amino]phenol (3,5-diBr-PASPAP),2-(5-bromo-2- pyridylazo)-5-[N-(3-sulphopropyl)amino]phenol and 2-(5-bromo-2-pyridylazo)-5-[N-propyl-N- (3-sulphopropyl)amino] phenol. With 3,5-diBr-PAESPAP the Fe(II) and Ni(II) chelates were not resolved, but resolution was achieved with 3,5-diBr-PASPAP. The calibration graphs were linear over the ranges 2.0–10.0 ng (10-μl injection) of Fe, Ni and Co and for 20–100 ng (10-μl injection) for V with 3,5-diBr-PAESPAP and 3,5-diBr-PASPAP.     

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.     

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.     

Selective spectrophotometric determination of vanadium in silicates with a new pyridylazophenol in the presence of hydrogen peroxide

The synthesis of a new heterocyclic azo compound, 2-(3,5-dibromo-4-methyl-2-pyridylazo)-5-diethylaminophcnol (3,5-Br-MEPADAP is described. The dye forms an intensely coloured (ε=4.11·10⁴ 1 mole^-1 cm^-1 at 615 nm) unstable chelate with vanadium(V) in weakly acidic medium. However, vanadium(V) reacts with 3,5-Br-MEPADAP and hydrogen peroxide in 0.5 M sulphuric acid to form a stable 1:1:1 ternary complex which is extractable in several solvents. In the presence of fluoride, the reaction is highly selective for vanadium(V); only large amounts of halides, oxidizing and reducing agents interfere. The effective molar absorptivity is 5.43 ·10⁴ 1 mole^-1 cm^-1 at 615 nm in chloroform. The reagent system was applied for the direct spectrophotometric determination of vanadium in a wide range of silicates; the average relative standard deviation was 0.45 %. The accuracy of the vanadium values obtained for ten international standard rocks compares well with the currently accepted most probable values.     

Sulfonated 1-(2-pyridylazo)-2-naphthols and 2-(2-pyridylazo)-1-naphthols as spectrophotometric reagents: Determination of nickel

Three sulfonated 1-(2-pyridylazo)-2-naphthols and six sulfonated 2-(2-pyridylazo)-1-naphthols were synthesized, and their application to the spectrophotometric determination of metals was studied. The acidity constants of the reagents and the stability constants of the nickel chelates are reported, and the relationship between their properties and the position of the sulfonic acid group is discussed. 1-(2-Pyridylazo)-2-naphthol-6-sulfonic acid (PAN-6S) and 1-(2-pyridylazo)-2-naphthol-7-sulfonic acid (PAN-7S) are sensitive and selective reagents for nickel. The determination of nickel in the presence of cobalt with PAN-6S is described. Extraction of the chelate as the ion-pair with tetraphenylarsonium ions into chloroform is suitable for the determination of 1–10 μg Ni at 570 nm; the molar absorptivity is 56 000 l mol^-1 cm^-1, and interferences are easily avoided.     

Spectrophotometric determination of nickel(II), palladium(II) and copper(II) in presence of each other and other ions with 1-(o-carboxyphenyl)-3-hydroxy-3-phenyltriazene

Summary 1-(o-Carboxyphenyl)-3-hydroxy-3-phenyltriazene was found to be an excellent spectrophotometric reagent for the determination of nickel(II), palladium(II) and copper(II). At pH 6.8–8.3, 2.4–3.5 and 2.2–3.8, nickel, palladium and copper form greenish yellow, yellowish orange and light green complexes with maximum absorption at 410, 410, 400 nm, respectively. The systems obey Beer's law with optimum ranges from 0.25 to 2.0 ppm for Ni(II), 0.5–4.0 for Pd(II) and 0.5–4.0 for Cu(II); the elements form 11 complexes with the instability constants 2.1×10^–5, 1.5×10^–5 and 2.0×10^–5, resepctively. Effects of other anions and cations on the colour systems have been studied and procedures for the determination of Ni(II), Pd(II) and Cu(II) in presence of each other are described.

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Spektrophotometrische Bestimmung von Nickel(II), Palladium(II) und Kupfer(II) nebeneinander und in Gegenwart anderer Ionen mit Hilfe von 1-(o-Carboxyphenyl)-3-hydroxy-3-phenyltriazen

Zusammenfassung Ni, Pd und Cu bilden mit dem Reagens bei pH 6,8–8,3, 2,4–3,5 bzw. 2,2–3,8 grünlich-gelbe, gelblich-orange bzw. hellgrüne Komplexe mit Absorptionsmaxima bei 410, 410 bzw. 400 nm. Das Beersche Gesetz wird in den Bereichen 0,25–2,0, 0,5–4,0 bzw. 0,5–4,0 ppm befolgt. Die Elemente bilden 11-Komplexe mit den Instabilitätskonstanten 2,1 · 10^–5, 1,5 · 10^–5 bzw. 2,0 · 10^–5. Der Einfluß anderer Kationen und Anionen wurde untersucht und Arbeitsvorschriften werden angegeben.

     

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.     

Extraction equilibria for the 4-(2-Pyridylazo)-Resorcinol-Nickel(II)-Quaternary-Ammonium salt system

The extraction equilibria of nickel(II)-PAR complexes with tetradecyldimethylbenzylammonium chloride(Q⁺Cl^?) are investigated. Two kinds of nickel complex are extracted by chloroform: Ni(HR)₂,nQ⁺Cl^?₍₀₎(?⁵⁰⁰ = 3.73·10⁴l mol^?1cm^?1) at about pH 5 and 2Q⁺ NiR^2-_2(o)(?⁵⁰⁰ = 8.08·10⁴ l mol^?1 cm^?1) at above pH 8.5. The extraction constant for 2Q⁺ NiR^2-_2(o) was evaluated as [2Q⁺ NiR^2-₂]₀/[NiR^2-₂] [Q⁺]² = 10^11.16 at μ = 0.1 (Na₂SO₄. Synergic extraction studies of the Ni(HR)₂ species under slightly acidic conditions show that the species is Ni(HR)₂(H₂O)₂in auqeous solution and is extracted into chloroform as the adduct Ni(HR)₂(TBP)₂ (?⁵³⁵ = 3.57·10⁴ l mol^?1 cm^?1. Based on the extraction behavior of these complexes, the structures of the Ni²⁺—PAR complexes are discussed.     

Simultaneous spectrophotometric determination of binary mixtures of nickel,cobalt and vanadium with 3-(picolydene)benzenesulphonic acid 2-hydroxybenzoylhydrazone

The synthesis and characterization of a water-soluble reagent, 3-(picolydene)benzenesulphonic acid 2-hydroxybenzoylhydrazone, is described. The reagent is stable in aqueous media. The colour reations with nickel(II), cobalt(III) and vanadium(V) ions in slightly acidic solutions have molar absorptivities in the range 1.4–3.6 × 10⁴ l mol^?1 cm^?1. Simultaneous determinations of Ni, Co and V in binary mixtures are possible. Interference data are reported.     

2-[2-(6-Methylbenzothiazolyl)azo]-5-Diethylaminobenzoic acid as a new analytical reagent for the spectrophotometric determination of nickel

A new thiazolylazo chromogenic reagent, 2-[2-(6-methylbenzo-thiazoly)azo]-5-diethylaminobenzoic acid (6-Me-BTAEB), has been synthesized. Its chromogenic reaction with microamounts of nickel in the presence of sodium dodecylsulfate (SDS) has been thoroughly studied. 6-Me-BTAEB reacts with nickel(II) in weak acid medium containing appropriate amounts of SDS to form a blue-violet complex with high sensitivity, good selectivity and high stability. The composition is found to be 1:2 (nickel to 6-Me-BTAEB) and its absorption maximum is at 650 nm with an apparent molar absorptivity of 1.67 × 10⁵l mole^–1 cm^–1. Beer's law is obeyed over the range 0-0.4 g of nickel per ml. The proposed method has been applied to the direct determination of nickel in aluminium alloys, pure magnesium and low alloy steels at the 0.2–0.3% (w:w) level with satisfactory results.     

Spectrophotometric Determination of Palladium(II) with n-Hydroxy-N,N-Diphenylbenzamidine and 1 -(2-Pyridylazo)-2-Naphthol

A spectrophotometric method to determine palladium(II) at trace levels is based on the extraction of palladium(II) as a binary complex with N-hydroxy-N,N′-diphenylbenzamidine (HDPBA) in chloroform at pH 5.0 ± 0.2. The complex shows maximum absorbance at 400 nm with molar absorptivity 6.4 × 10³ L mol^?1 cm^?1. The sensitivity of the Pd(II)-HDPBA complex was enhanced by the addition of l-(2-pyridylazo)-2-naphthol (PAN). The green coloured complex shows maximum absorbance at 620 nm with molar absorptivity 1.58 × 10⁴ L mol^?1 cm^?1. Sandell's sensitivity and the detection limit of the method are 0.0067 μg cm^?2and 0.1 μg Pd(II) mL^?1, respectively. Most common metal ions associated with palladium metal do not interfere. The effects of various analytical parameters on the extraction of the metal are discussed.     

Study of the solid phase extraction and spectrophotometric determination of nickel using 5-(4′-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione in environmental samples

A rapid, sensitive and selective method for the determination of nickel based on the rapid reaction of nickel(II) with 5-(4′-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (CPAHPD) and the solid phase extraction of the Ni(II)–CPAHPD complex with C18 membrane disks has been developed. In the presence of pH 6.8 buffer solution and cetylpyridinium bromide (CPB) medium, CPAHPD reacts with nickel to form a red complex of a molar ratio of 1:1 (nickel to CPAHPD). This complex was enriched by solid phase extraction (SPE) with C18 membrane disks. An enrichment factor of 100 was obtained by elution of the complex from the disks with the minimal amount of isopentyl alcohol. The molar absorptivity and Sandell sensitivity of the complex was 3.11 × 10⁵ L mol^?1 cm^?1 and 0.0189 ng cm^?2, respectively at 549 nm in the measured solution. Beer's law was obeyed in the range of 0.01–0.37 μg mL^?1, while that obtained by Ringbom plot was in the range of 0.025–0.35 μg mL^?1. The detection and quantification limits were calculated and found to be 0.003 and 0.01 μg mL^?1. The proposed method was applied to the determination of nickel in water, food, biological and soil samples with good results.     

Sensitive spectrophotometric determination of La(III) with 1-(2-pyridylazo)-2-naphthol

A simple and sensitive method for spectrophotometric determination of lanthanum has been developed. At pH 9.6, in presence of 50% ethanol, lanthanum reacts with 1-(-2-pyridylazo)-2-naphthol (PAN) to form a red complex which has two absorption maxima, at 545 and 510 nm. The molar absorptivity at 545 nm is 0.55 × 10⁴ liters · mol^?1 cm^?1. On the other hand, lanthanum reacts with PAN in pure ethanol to form a red complex at 530 nm, with high molar absorptivity (8 × 10⁴ liters · mol^?1 cm^?1).     

Pre-column chelation liquid chromatographic separation and determination of trace V,Cu, Co,Pd, Fe and Ni

Conditions for the separation by reversed-phase liquid chromatography (LC) of V(V), Cu(II), Co(III), Pd(II), Fe(III) and Ni(II) chelates with 2-(5-bromopyridylazo)-5-diethylaminophenol (5-Br-PADAP) were studied. Six species of metal chelates were separated successfully with methanol-acetonitrile-water (72:12:16, v/v/v) containing 0.13 M NaCl and 0.29 mM cetyltrimethylammonium bromide (pH 5.0) as the mobile phase on a Nucleosil C₁₈ (5 μm) column (250 × 4 mm i.d.).The conditions of the determination of these metal chelates are discussed. A simple and rapid method for the determination of trace amounts of V(V), Cu(II), Co(III), Pd(II) and Ni(II) simultaneously by reversed-phase LC has been developed. The detection limits are 5 × 10^?12, 1 × 10^?10, 3 × 10^?11, 5.3 × 10^?9 and 2 × 10^?10 g, respectively. The method is applied to the determination of these metals in natural waters and mineral samples.     

Ternary Complex Nickel(II)/3-(4′,5′-Dimethyl-2′-Thiazolylazo)-2,6-Dihydroxybenzoic Acid/Cyanide. Spectrophotometric Determination of Nickel

Abstract

A spectrophotometric method for nickel has been developed based on the formation of a ternary complex in the system Ni(II)/3-(4′,5′-dimethyl-2′-thiazolylazo)-2,6-dihydroxybenzoic acid/cyanide at pH 9.2 (borate buffer), which allows the determination of 0.05–0.47ppm of nickel (ε = 3.53×10⁴ 1.mol^?1. cm^?1) at 538nm. Interferences have been studied and the method applied to the determination of nickel in low alloy steels.     

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.