Mohamed M. Seleim

Spectrophotometric study of the complexation equilibria of zirconium(IV) with 1-amino-4-hydroxyanthraquinone and the determination of zirconium

The spectral absorption and acid-base characteristics of 1-amino-4-hydroxyanthraquinone (AMHA) were studied in water-ethanol media. The composition, molar absorptivities, equilibrium constants and stability constants of the chelates of this reagent with zirconium(IV) have been determined spectrophotometrically in 40%V/V ethanol at 20 °C and an ionic strength of 0.1 M(NaClO4). Graphical logarithmic analysis of the absorbance graphs was used to demonstrate and characterise the complexation equilibria in solution. A simple, rapid, selective and sensitive method for the spectrophotometric determination of trace amounts of zirconium is proposed based on the formation of the Zr(AMHA)2 complex at pH 3.5 (λmax.= 600 nm, Iµ= 1.621 × 104 l mol–1 cm–1). Interference caused by a number of ions was masked by the addition of cyanide ions.

Solution equilibria and stability of the complexes of pyridinecarboxylic acids: Complexation reaction of mercury(II) with 2-hydroxynicotinic acid

SummaryThe solution equilibria of 2-hydroxynicotinic acid (hyna) complexes with mercury(II) have been studied spectrophotometrically in 50% (v/v) ethanol at 20°C and an ionic strength of 0.1mol dm−3 (NaClO4). Three mercuric complexes are formed in solution in dependence on the acidity of the medium. The basic characteristics of the different complexes are determined and the analytical aspects of the complexation reaction are demonstrated. A critical investigation has also been presented of the solution equilibria and stability of the mixed complex of mercury(II) withhyna and thiosalicylic acid (tsa). The various complex transitions leading to the formation of the 1 : 1 : 1 Hg(tsa)(hyna) ternary complex in solution are investigated. The non-charged mono-ligand complex Hg(hyna) is used for UV-spectrophotometric determination of mercury atpH 4.5–5 (λmax=325nm, ɛ=0.8·104lmol−1cm−1). The system obeyed Beers law up to 36.1 µg ml−1 of Hg(II). The optimum concentration range (Ringbom) is between 6 and 28.5µg ml−1. Interference caused by a number of ions was masked by the addition of fluoride ions.ZusammenfassungDie Lösungsgleichgewichte von 2-Hydroxynikotinsäure (hyna) mit Hg(II) wurde spektrophotometrisch in 50% (v/v) Ethanol bei 20°C und einer Ionenstärke von 0.1 mol dm−3 (NaClO4) untersucht. In Abhängigkeit von der Acidität des Mediums werden drei Quecksilberkomplexe gebildet. Die grundlegenden Charakteristika der Komplexe wurden bestimmt und die analytischen Aspekte aufgezeigt. Die gemischten Komplexe von Hg(II) mithyna und Thiosalicylsäure (tsa), insbesondere die verschiedenen Komplexübergänge zum ternären 1 : 1 : 1 Hg(tsa)(hyna)-Komplex, wurden ebenfalls untersucht. Der ungeladene Monoligandenkomplex Hg(hyna) kann beipH 4.5–5 zur UV-spektroskopischen Quecksilberbestimmung eingesetzt werden (λmax=325nm, ɛ=0.8·104lmol−1cm−1). Das System gehorcht bis zu einer Hg(II)-Konzentration von 36.1µgml−1 dem Beerschen Gesetz. Der optimale Konzentrationsbereich (Ringbom) liegt zwischen 6 und 28.5µgml−1. Interferenzen mit einer Reihe anderer Ionen konnten durch Maskierung mit Fluoridionen umgangen werden.

Reaction of mercury(II)-thiosalicylate complex with picolinic acid and ultraviolet spectrophotometric determination of mercury(II)

The monothiosalicylate complex of mercury(II) reacts with picolinic acid (PIC) to form a ternary complex which has an absorption maximum at 295 nm in 50%V/V ethanol-water in the pH range 6.3–7.5. Beers law is obeyed up to a 20.15 µg ml–1 concentration of HgII. The molar absorptivity of the ternary complex is 0.86 m2 mol–1 at 295 nm and the sensitivity for the HgII ion is 5.2 × 10–3µg cm–2 per 0.001 absorbance unit. The composition of the ternary complex is estimated to be Hg(TSA)(PIC). A number of ions which interfere with the determination could be masked by the addition of EDTA or fluoride ions as masking agents. Further information on the complex-forming equilibria and stability of the HgII ternary complex was obtained by potentiometric titrations at 20 ± 0.1 °C and 0.1 M(NaClO4) ionic strength.

Solution equilibria of pyridinecarboxylic acids : complexation reaction of 2-mercaptonicotinic acid-copper(II) complex with thiosalicylic acid

The reaction of 2-mercaptonicotinic-copper (II) complex (Cu2+-MENA, 1 3n 1) with thiosalicylic acid (TSA) has been investigated spectrophotometrically in ethanol-water solution (50%, v/v) at I=O.IM (NaClO4) and 25°C. Under the acidic conditions encountered in this study, there are competing equilibria between protonation of the Cu2+-MENA binary chelate, the formation of the Cu(MENA)(TSA) ternary complex and protonation of the second ligand (TSA). The equilibrium constants for the complexation reactions and the stability of the mixed-ligand complex are determined. The optimum conditions for the predominance of the ternary complex are established and the enhancement of this complex over binary complex formation is evaluated. Complex-forming equilibria have also been examined by potentiometric-pH titrations and the experimental data are discussed in relation to various equilibria existing in solution. Structural and bonding features of the mixed-ligand complex are illustrated from considerations of the IR spectral data.

Ternary complexes in solution: mixed-ligand complexes of thorium(IV) with alizarin maroon and secondary ligands containing oxygen or nitrogen as donor atoms

The stability constants of the Th(IV) complexes containing Alizarin Maroon (AZM) and as a secondary ligand (L) salicylic acid (SA), 5-sulphosalicylic acid (SSA), 5-nitrosalicylic acid (NSA), 2,2′-bipyridyl (bipy) or 1,10-phenanthroline (phen) were determined potentiometrically at 25 °C with an ionic strength (l) of 0.1 M(NaCIO4), and in a 20%V/V aqueous ethanol medium.All of these mixed-ligand complexes are more stable than one would expect. The stability of the ternary complexes is discussed in relation to the natures of the secondary ligands involved. The solution spectrum of the complex is characterised by an absorption band with λmax. at 580 nm within the pH range 4.6–5.5. The ternary system obeys Beers law between 2.3 and 22.5 µg ml–1 of thorium with a molar absorptivity of 1.1 × 104 l mol–1 cm–1. Finally, a sensitive method has been developed for the micro-determination of thorium based on the formation of the Th-AZM-SSA ternary complex.

Use of Quinizarin as a Spectrophotometric Reagent for MgO Content Analysis of Portland Cement and Cement Clinker

Summary. A new direct spectrophotometric method for the determination of magnesium oxide in Portland cement and cement clinker is proposed. The method is based on a reaction with quinizarin (QUIN, 1,4-dihydroxyanthraquinone) in ethanol-water (50% v/v) solution at pH=9.5–10.3. Under optimum conditions, the determination of 0.5–3.9 μgċml−1 of magnesium is possible. The method is rapid and selective and possesses good accuracy and precision. The analysis of cement materials of variable magnesium content is feasible over the concentration range of 0.85–3.2 μgċml−1 Mg; the detection limit is 25.3 ngċml−1 Mg. Under the given conditions, no constituents normally present in Portland cement materials interfer. The procedure was tested by analyzing several standard reference materials and real samples of Portland cement and has been found to give satisfactory results. It has been satisfactorily applied to the determination of magnesium in clay and raw meal.Zusammenfassung. Eine neue Methode zur direkten spektrophotometrischen Bestimmung von Magnesiumoxid in Portlandzement und Zementklinker wird vorgestellt. Sie beruht auf einer Reaktion mit Chinizarin (QUIN, 1,4-Dihydroxyanthrachinon) in einem Ethanol-Wasser-Gemisch (50% v/v) bei einem pH-Wert von 9.5–10.3. Unter optimalen Bedingungen können 0.5–3.9 μg Mg pro ml bestimmt werden. Die Methode ist rasch und selektiv und zeichnet sich durch hohe Genauigkeit und Präzision aus. Die Analyse von Zementen mit unterschiedlichem Magnesiumgehalt ist über einen Konzentrationsbereich von 0.85–3.2 μgċml−1 Mg möglich. Die Nachweisgrenze liegt bei 25.3 ngċml−1 Mg. Unter den gegebenen Bedingungen treten bei gängigen Verunreinigungen im Zement keine Störungen auf. Die Methode wurde an verschiedenen Standards und an reellen Proben getestet und mit zufriedenstellenden Ergebnissen zur Bestimmung von Magnesium in Lehm und Rohmahlgut eingesetzt.

New spectrophotometric method for the determination of trace amounts of palladium

SummaryA simple, rapid, selective, and sensitive method for the spectrophotometric determination of palladium is developed based on the reaction of Pd(II) with 1-amino-4-hydroxyanthraquinone (AMHA). The reaction is carried out atpH 3.8 in 50% (v/v) ethanol-water medium. The molar absorptivity of the complexed ligand is 1.1 · 104 l mol−1 cm−1 at 620 nm. Calibration plots are linear up to 17 µg Pd cm−3. The optimum concentration range (Ringbom plot) is between 3–14.5 µg cm−3. The spectral study of the reaction in solutions containing equimolar concentrations or an excess of one component, in thepH range ∼ 0.3–6.5, indicate the possible complex transitions that occur in solution. Complete graphical and logarithmic analysis of the absorbance-pH graphs was performed to demonstrate and characterize the complexation equilibria in solution. Under the optimum conditions, palladium can be determined as the noncharged complex Pd(AMHA)2 in the presence of a large number of foreign ions. Interferences caused by zirconium(IV) could be masked with fluoride ions.ZusammenfassungEine einfache, schnelle und empfindliche Methode für die spektrophotometrische Bestimmung von Palladium wurde auf der Basis der Reaktion von Pd(II) mit 1-Amino-4-hydroxyanthrachinon (AMHA) entwickelt. Die Reaktion wird in 50% (v/v) Ethanol/Wasser beipH 3.8 ausgeführt. Die molare Absorption des komplexierten Liganden beträgt 1.1 · 104 l mol−1 cm−1 bei 620 nm. Kalibrierungskurven verlaufen bis zu 17 µg Pd cm−3 linear. Der optimale Konzentrationsbereich (Ringbom-Plot) liegt zwischen 3 und 14.5 µg cm−3. Spektroskopische Untersuchungen der Reaktion in Lösungen, entweder mit equimolaren Konzentrationen oder mit einem Überschuß an einer Komponente impH-Bereich ∼ 0.3–6.5, lassen Rückschlüsse auf mögliche Komplex-Übergänge in Lösung zu. Es wurde eine vollständige graphische, logarithmische Analyse der Absorptions-pH-Graphen durchgeführt, um die Komplexgleichgewichte in Lösung aufzuklären und zu charakterisieren. Unter den Optimalbedingungen kann Palladium als nichtgeladener Komplex Pd(AMHA)2 in Gegenwart einer großen Anzahl an Fremd-Ionen bestimmt werden. Schwierigkeiten mit Zirkonium(IV) konnte durch Maskierung mit Fluorid-Ionen umgangen werden.

Physico-chemical study of mixed-ligand selenium(IV) complexes: ternary complex of selenium(IV) with alizarin maroon and eosin

The reaction of selenium(IV) with alizarin maroon (AZM) as a primary ligand and eosin as a secondary ligand was examined spectrophotometrically and potentiometrically at 20 ± 0.1 °C and an ionic strength of 0.1 M(perchloric acid). The solution spectra of the mixed-ligand complex formed is characterised by an absorption band with λmax. at 560 nm within the pH range 6.5–7.2. The pink selenium-(AZM)2-(eosin)2 association complex conformed to Beers law over the concentration range 0.16–2.0 µg ml–1 of selenium with a molar absorptivity of 2.5 × 104 l mol–1 cm–1.

Spectral properties and analytical application of the ternary complex of lanthanum(III) with 1,10-phenanthroline and eosin

Abstract The pink lanthanum—(1,10-phenanthroline)2—(eosin)2 complex is used to determine 0.5–10 × 10-5 M lanthanum, either in aqueous solution or chloroform. In the presence of EDTA, only aluminium and cyanide interfere.

Die Reaktion von Ce(III), Th(IV) und U(VI) mit Chinizaringrün und seinem nichtsulfonierten Grundkörper

The reaction of 1,4-(2′-sulpho-4′-methylanilino)anthraquinone (quinizarin green,QG) and its non-sulphonated derivative (NSQG) with Ce(III), Th(IV), and U(VI) was investigated. Spectrophotometric and conductometric studies were carried out to investigate the stoichiometry of the complexes formed. The studies revealed the formation of 1∶1 and 1∶2 (M∶L) complexes. The apparent stability constants of the different complexes were determined. The structure of the ligand in the solid chelates was studied by IR spectrophotometry which showed that the chelate formation takes place through the oxygen of the C=O group and the α-imino nitrogen.