Sensitive spectrofluorimetric determination of aluminium(III) with Eriochrome Red B

A spectrofluorimetric method is reported for the determination of Al(III), based on the formation of a fluorescent Al(III)-Eriochrome Red B complex in the presence of hexamethylenetetramine at 60°C. Fluorescence measurements were made at 2°C and all variables that affect the development of the complex are reported. The method is very selective and the detection limit is 0.1 ng ml^?1. It was applied to the determination of Al(III) in tap water.     

Reverse flow injection spectrophotometric determination of iron(III) using norfloxacin

A reversed flow injection colorimetric procedure for determining iron(III) at the μg level was proposed. It is based on the reaction between iron(III) with norfloxacin (NRF) in 0.07 mol l⁻¹ ammonium sulfate solution, resulting in an intense yellow complex with a suitable absorption at 435 nm. Optimum conditions for determining iron(III) were investigated by univariate method. The method involved injection of a 150 μl of 0.04% w/v colorimetric reagent solution into a merged streams of sample and/or standard solution containing iron(III) and 0.07 mol l⁻¹ ammonium sulfate in sulfuric acid (pH 3.5) solution which was then passed through a single bead string reactor. Subsequently the absorbance as peak height was monitored at 435 nm. Beer's law obeyed over the range of 0.2–1.4 μg ml⁻¹ iron(III). The method has been applied to the determination of total iron in water samples digested with HNO₃–H₂O₂ (1:9 v/v). Detection limit (3σ) was 0.01 μg ml⁻¹ the sample through of 86 h⁻¹ and the coefficient of variation of 1.77% (n=12) for 1 μg ml⁻¹ Fe(III) were achieved with the recovery of the spiked Fe(III) of 92.6–99.8%.     

The reaction between oxalatotetraammine-cobalt(III) ion and hydroxide ion in aqueous solution

The rate of the reaction between sodium hydroxide and oxalatotetraamminecobalt(III) ion was measured for a variety of hydroxide ion concentrations and at four temperatures. The rate law below 333 K is given by k_obs = k₀ + k₂[OH⁻]² and above 333 K is shown to be k_obs = k₀ + k₁[OH⁻]. The reaction proceeds with a single rate controlling step, which is interpreted as oxalate ring opening. This is followed by a rapid oxalate loss step.     

Reaction of aluminium chloride with poly(divinyl benzene) particles--a reaction kinetic study using infrared spectroscopy

Porous poly(para-divinylbenzene) and poly(meta-divinylbenzene) particles were synthesised from para-divinylbenzene and meta-divinylbenzene monomers with toluene and 2-ethylhexanoic acid as porogens. The residual vinyl groups in the particles were thereafter reacted using aluminium chloride with dichlorobenzene as a catalyst. The conversion of vinyl groups was followed by analysing polymer particles taken from the reaction mixture at different time intervals. Infrared spectroscopy both in the mid and near infrared region was used as the analytical technique. The intensity changes in the overtone absorption at 1628 nm due to the vinyl bonds were used as the basis for the quantification of the vinyl group consumption. Infrared spectra of the particles in the mid IR were also measured to understand changes taking place in the polymer matrix during the reaction. The results indicated that residual vinyl groups in these polymer particles were consumed during the reaction with aluminium chloride. The reaction of aluminium chloride with the polymer matrix was explained by proposing mechanisms for the formation of different products during the reaction. The complex formed between aluminium chloride and the residual vinyl groups seemed to induce addition of HCl to the vinyl group or leads to crosslinking and/or cyclisation in the case poly(para-DVB) particles. The reaction of aluminium chloride with poly(meta-DVB) takes place to a lesser extent.     

Reverse flow injection spectrophotometric for determination of aluminium(III)

A reverse flow injection analysis (rFIA) spectrophotometric method has been developed for the determination of aluminium(III). The method was based on the reaction of Al(III), quercetin and cetyltrimethylammonium bromide (CTAB), yielding a yellow colored complex in an acetate buffer medium (pH 5.5) with absorption maximum at 428 nm. The rFIA parameters that influence the FIA peak height have been optimized in order to obtain the best sensitivity and minimum reagent consumption. A linear relationship between the relative peak height and Al(III) concentrations were obtained over the concentration range of 0.02-0.50 mg L⁻¹ with a correlation coefficient of 0.9998. The limit of detection (LOD, defined as 3σ) and limit of quantification (LOQ, defined as 10σ) were 0.007 and 0.024 mg L⁻¹, respectively. The repeatability was 1.10% (n = 11) for 0.2 mg L⁻¹ Al(III). The proposed method was applied to the determination of Al(III) in tap water samples with a sampling rate of 60 h⁻¹. Results obtained were in good agreement with those obtained by the official ICP-MS method at the 95% confidence level.     

Development of a new analytical method for online simultaneous qualitative determination of aluminium (free aluminium ion, aluminium-fluoride complexes) by HPLC-FAAS

The paper presents a novel method for simultaneous online examination of inorganic forms of aluminium: AlF₂⁺, AlF^2+, and Al³⁺ by means of the high performance liquid chromatography hyphenated with a detection by the atomic absorption spectrometry with flame atomization (HPLC-FAAS) without post-column reaction. The application of optimization procedure conditions of chromatographic separation of inorganic forms of aluminium was achieved by the analytical column IonPac CS5A (Dionex) with guard column IonPac CG5A (Dionex) and an aqueous ammonium chloride mobile phase, at pH about 3 with gradient elution. The separation of Al forms with nominal charge of 1+, 2+, 3+ required a run time of less than 8 min during a single analysis. The proposed method has been successfully used for the examination of aluminium forms formation AlF_n⁽³⁻ⁿ⁾⁺ in environmental samples.     

Determination of aluminium(III) in water samples in a microemulsion system by spectrofluorimetry

The sensitizing effect of cetyltrimetrylammonium bromide (CTAB) microemulsion media on the determination of aluminium(III) by spectrofluorimetry was developed. The main factors affecting the determination were investigated in detail. The results showed that 8-hydroxyquinoline (HQ) react with aluminium(III) forming a complex with fluorescence in the system of potassium acid phthalate-NaOH buffer solution at pH 6.0, the maximum excitation and emission wavelengths are at 380.0 and 502.6 nm, the sensitizing effect of CTAB microemulsion is higher than that of CTAB micelle. The proposed method has been applied to the determination of aluminium(III) in tap water and lake water samples with satisfactory results.     

Thermodynamic studies of sitting-atop complexation between free base meso-tetraarylporphyrins and antimony(III) chloride in chloroform

Interaction of para, meta and ortho-substituted meso-tetraarylporphyrins, (H₂t(X)pp, X: OMe, Me, H and Cl) with SbCl₃ in chloroform solution afforded 1 : 1 sitting-atop (SAT) complexes ([(SbCl₃)(H₂t(X)pp)]). The formation constants were calculated by KINFIT and found to decrease with increasing temperature. The thermodynamic parameters, ΔH°, ΔS° and ΔG°, were obtained. Formation constants of these complexes change with changing substituent (X) on the aryl rings of H₂t(X)pp in the following order: (SbCl₃)H₂t(4-OMe)pp >?(SbCl₃)H₂t(4-Me)pp >?(SbCl₃)H₂tpp >?(SbCl₃)H₂t(4-Cl)pp >?(SbCl₃)H₂t(3-OMe)pp >?(SbCl₃)H₂t(3-Me)pp> (SbCl₃)H₂t(2-OMe)pp >?(SbCl₃)H₂t(2-Me)pp.     

Kinetics and mechanism of the complexation between hydroxopentaaquochromium(III) and octacyanomolybdate(IV) ions in acidic medium

Summary The reaction between hydroxopentaaquochromium(III) and octacyanomolybdate(IV) was investigated spectrophotometrically and obeyed a 2:1 reactant stoichiometry with respect to formation of the [Cr(H₂O)₄OH]₂ Mo(CN)₈ complex. Kinetic studies reveal that the reaction is first order with respect to hydroxopentaaquochromium(III) in the presence of an excess of octacyanomolybdate(IV). The reaction rate increased with an increase in the ionic strength and temperature, and decreased with an increase in hydrogen ion concentration. A mechanism has been proposed based upon ion-pair formation. The results are best accounted for by the Eigen-Tamm mechanism. Anation of [Cr(H₂O)₅OH]²⁺ is discussed in terms of an associative interchange (I _a) where bond breaking and bond making are equally important. The activation parameters were calculated using Arrhenius's equation.     

Potentiometric studies on the complexation equilibria between some trivalent lanthanide metal ions and biologically active 2-hydroxy-1-naphthaldehyde thiosemicarbazone (HNATS)

Summary The chelation behaviour of some trivalent lanthanide and yttrium metal ion with biologically active 2-hydroxy-1-naphthaldehyde thiosemicarbazone (HNATS) has been investigated by potentiomotric measurements at 20±0.5°C in 75% (v/v) dioxane-water medium at various ionic strengths of sodium perchlorate. The method of Bjerrum and Calvin, as modified by Irving and Rossotti has been used to find out the values of (average number of ligand bound per metal ion) andpL (free ligand exponent). The formation constants of metal chelates have been computed on a PC-XT computer, using a program patterned after that of Sullivan et al. to give _n values using weighted least squares method. TheS _min values (S _min =²) have been calculated. The order of formation constants of chelates was found to be: La³⁺3+3+3+3+3+3+3+3+3+. The formation constants of the chelates formed have been correlated to size and ionization potentials of the metal ions.

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Potentiometrische Untersuchungen der Komplexierungsgleichgewichte zwischen einigen trivalenten Metallionen und biologisch aktivem 2-Hydroxy-1-naphthaldehyd-thiosemicarbazon (HNATS)

Zusammenfassung Es wurde das Chelierungsverhalten einiger trivalenter Lanthanidenionen mit biologisch aktivem 2-Hydroxy-1-naphthaldehyd-thiosemicarbazon (HNATS) mittels potentiometrischer Messungen bei 20±0.5°C in 75% (v/v) Dioxan-Wasser bei verschiedener Ionenstärke an Natriumperchlorat untersucht. Die Methode nach Bjerrum und Calvin in der Modifikation nach Irving und Rossotti wurde zur Ermittlung der Werte (mittlere Anzahl an Liganden pro Metallion) undpL (Exponent an freiem Liganden) verwendet. Die Komplexbildungskonstanten wurden in Anlehnung an Sullivan et al. an einem PC-XT Computer errechnet. DieS _min-Werte (S _min=²) wurden ebenfalls bestimmt. Die Reihung der Chelatbildungskonstanten war: La³⁺3+3+3+3+3+3+3+3+3+. Die Bildungskonstanten sind mit der Größe und dem Ionisierungspotential der Metallionen zu korrelieren.

     

High-performance liquid chromatography of 8-hydroxyquinoline chelates of aluminium and cobalt(III)

Summary The 8-hydroxyquinoline chelates of Co(III) and Al(III) may be separated by high-performance liquid chromatography using a silica column and 5% methanol in chloroform as mobile phase. Using detection at 254 nm, the method provided detection limits of 0.9 ng of Co(III) and 17 ng of Al(III) in a 10 mm³ injection.     

Potentiometric study of the protonation and binary complexation equilibria between the hydrogen ion,copper(II) ion and zinc(II) ion and the picolinate ion in dioxane-water mixtures

Protonation constants of picolinic acid and stability constants of Cu(II) and Zn(II) picolinate complexes were determined potentiometrically in 50% (v/v) dioxane-water solution at 25°C and 0.2 M KNO₃. The values obtained for the constants were: protonation constants for picolinate ion: logβ₁ = 5.36±0.01 and logβ₂ = 6.80±0.04; stability constants for copper(II) complexes: logβ_1.1 = 7.766±0.001 and logβ_1.2 = 16.826±0.007; stability constants for the Zn(II) complexes: logβ_1.1 = 6.10±0.05, logβ_1.2 = 11.47±0.03 and logβ_1.3 = 15.77±0.08. No protonated nor hydroxo-complex was detected in the metal ion-picolinate systems.     

Potentiometric and Multinuclear Magnetic Resonance Study of the Solution Equilibria Between Aluminium(III) Ion and L-Aspartic Acid

Summary. Solution equilibria between aluminium(III) ion and L-aspartic acid were studied by potentiometric, ²⁷Al, ¹³C, and ¹H NMR measurements. Glass electrode equilibrium potentiometric studies were performed on solutions with ligand to metal concentration ratios 1:1, 3:1, and 5:1 with the total metal concentration ranging from 0.5 to 5.0 mmol/dm³ in 0.1 mol/dm³ LiCl ionic medium, at 298 K. The pH of the solutions was varied from ca. 2.0 to 5.0. The non-linear least squares treatment of the data performed with the aid of the Hyperquad program, indicated the formation of the following complexes with the respective stability constants log β_p,q,r given in parenthesis (p, q, r are stoichiometric indices for metal, ligand, and proton, respectively): Al(HAsp)²⁺ (log β_1,1,1 = 11.90 ± 0.02); Al(Asp)⁺ (log β_1,1,0 = 7.90 ± 0.03); Al(OH)Asp⁰ (log β_1,1,−1 = 3.32 ± 0.04); Al(OH)₂Asp⁻ (log β_1,1−2 = −1.74 ± 0.08), and Al₂(OH) Asp³⁺ (log β_2,1,−1 = 6.30 ± 0.04). ²⁷Al NMR spectra of Al³⁺ + aspartic acid solutions (pH 3.85) indicate that sharp symmetric resonance at δ∼10 ppm can be assigned to (1, 1, 0) complex. This resonance increases in intensity and slightly broadens upon further increasing the pH. In Al(Asp)⁺ complex the aspartate is bound tridentately to aluminum. The ¹H and ¹³C NMR spectra of aluminium + aspartic acid solutions at pH 2.5 and 3.0 indicate that β-methylene group undergoes the most pronounced changes upon coordination of aluminum as well as α-carboxylate group in ¹³C NMR spectrum. Thus, in Al(HAsp)²⁺ which is the main complex in this pH interval the aspartic acid acts as a bidentate ligand with –COO⁻ and –NH₂ donors closing a five-membered ring.     

Zirconium ion selective electrode based on bis(diphenylphosphino) ferrocene incorporated in a poly(vinyl chloride) matrix

A novel potentiometric zirconium - PVC matrix membrane sensor incorporating bis(diphenylphosphino) ferrocene as an electroactive material and tris(2-ethylhexyl)phosphate as solvent mediator is described. In mixed acetate buffer solution of pH 4.8, the sensor displays a rapid and linear response for zirconium ion over the concentration range 1.0 × 10⁻¹ to 1.0 × 10⁻⁷ mol L⁻¹ with a good slope of 59.7 ± 0.3 mV per decade and detection limit 1.8 × 10⁻⁸ mol L⁻¹. The best performance was obtained with membrane composition 33% PVC, 65% TEHP, 1% NaTPB and 1% ionophore. The proposed electrode revealed excellent selectivity for zirconium ion over a wide variety of alkali, alkaline earth, transition and heavy metal ions and could be used in a pH range of 4.15-7.8. The electrode was applied for at least 1 month without any considerable divergence in the potential responses. The practical utility of the electrode has been demonstrated by its use as an indicator electrode in the potentiometric titration of zirconium ions with sodium fluoride and in determination of zirconium ion in some alloy, tape and waste water samples.     

Chromotropic acid,a fluorogenic chelating agent for aluminium(III)

Complexation of aluminium(III) with the fluorogenic ligand chromotropic acid (4,5-dihydroxynaphthalene-2,7-disulfonic acid) has been revisited with the aim of using enhancement of the fluorescence intensity as an analytical tool. Complexation at the optimum pH4 was shown to lead to a 1:1 complex with a stability constant log ₁₁₀=18.4±0.7. The fluorogenic effect was thoroughly investigated. Nearly selective excitation of the chelate rather than the ligand could be achieved at wavelengths longer than 360 nm. For analytical purposes the main interfering ion was Ga³⁺. The strongest competing ligand was shown to be citric acid. Competitive complexation by acetate or formate ions can also make their use in a buffer at the usual concentration, 0.2 mol L^–1, questionable, whereas a 10^–2 mol L^–1 formic acid buffer was shown to be a good alternative. The calibration plot showed that the dependence of response on Al(III) concentration was linear up to 500 g L^–1; the detection limit was 0.65 g L^–1 (3SD _blank, n=10, SD=±1.4% at 10 g L^–1 and ±0.8% at 100 g L^–1). The analytical procedure was successfully applied to several samples of tap water and the results were in good agreement with those from AAS determination.     

Redox equilibria in the In(III)-In(I)-In system in aqueous KBr solutions,I. Potentiometric and coulometric study

Summary The reproportionation of In(I) ions in acidic potassium bromide solutions was studied by means of the coulometric and potentiometric method. The formal potentials of the In(III)/In(I), In(III)/In and In(I)/In redox couples as well as the equilibrium constants of the reaction In(III)+2 In=3 In(I) were determined at a background electrolyte concentration ranging from 1 to 4 mol dm^–3. Based on the experimental results, a scheme of the reproportionation reaction was proposed with regard to the participation of bromide ions. In addition, the diffusion coefficient of In(I) ions was determined using the chronopotentiometric technique.

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Das Redox-Gleichgewicht im In(III)-In(I)-In-System in wäßrigen KBr-Lösungen, I. Potentiometrische und coulometrische Untersuchungen

Zusammenfassung Die Reproportionierung von In(I)-Ionen in sauren Kalium-bromid-Lösungen wurde mittels der coulometrischen und potentiometrischen Meßmethode untersucht. Die Formal-Standardpotentiale der In(III)/In(I)-, In(III)/In- und In(I)/In-Redoxpaare sowie die Gleichgewichts-konstanten der Reaktion In(III)+2 In=3 In(I) wurden im Konzentrationsbereich von 1–4 mol dm^–3 ermittelt. Mit der Steigerung der KBr-Konzentration verschiebt sich das untersuchte Gleichgewicht erheblich zugunsten Indium(I). Aufgrund der potentiometrischen Meßergebnisse wurde ein Schema der Reproportionierung-Reaktion unter Berücksichtigung der Teilnahme von Bromidionen aufgestellt. Zusätzlich wurde der Diffusionskoeffizient von In(I)-Ionen mit Hife chronopotentiometrischer Messungen bestimmt.

     

Characterization of an aluminium(III)–citrate species by means of ion chromatography with inductively coupled plasma-atomic emission spectrometry detection

The aluminium(III)–citrate complex (NH₄)₄[Al₂(C₆H₄O₇)(C₆H₅O₇)₂]·4H₂O was characterized using anion exchange chromatography on-line coupled with the element specific ICP-AES detector. Time-dependent monitoring of individual species in aqueous solution at different temperatures gave information about the species stability and the decomposition pathway. The aluminium–citrate complex (NH₄)₄[Al₂(C₆H₄O₇)(C₆H₅O₇)₂]·4H₂O disintegrated via an unknown intermediary Al(III)–citrate species from which the thermodynamically stable complex [Al₃(C₆H₄O₇)₃(OH)(H₂O)]⁴⁻ was formed. The activation energy for the decomposition reaction and the pre-exponential factor were determinated to be E_a = 81.95 kJ mol⁻¹ and A = 3.62 × 10¹³ s⁻¹.     

The kinetics and mechanism of reaction between ethylenediaminetetraacetomanganate(III) and cyanide ion

Summary The title reaction has been followed spectrophotometrically at 325 nm (_max of [Mn(CN)₆]^3–) under pseudo-first order conditions with cyanide in a large excess at pH=10.0, I=0.1M (NaClO₄) and 25°C. The reaction follows first-order kinetics in [MnEDTA(OH)]^2– and exhibits variable-order dependence in [CN^–] one at high cyanide concentration, and two at low cyanide concentration. The product of above reaction has been identified as [Mn(CN)₆]^3–.The kinetics of the reverse reaction,i.e., the reaction of [Mn(CN)₆]^3- with EDTA^4– have also been followed spectrophotometrically. This reactions is first-order with respect to both [Mn(CN) ₆ ^3– ] and [EDTA^4–] and exhibits an inverse first-order dependence on [CN^–]. A six-step mechanism has been proposed in which the penultimate step is rate-determining. The activation parameters have been obtained and support the postulated mechanism.