Adsorptive stripping voltammetric measurements of trace amounts of platinum(II) and ruthenium(III) in the presence of 1-(2-pyridylazo)-2-naphthol

An extremely sensitive stripping voltammetric procedure for low level measurements of platinum (II, IV) or ruthenium (III, IV) is reported. The method is based on the interfacial accumulation of the platinum (II) or ruthenium (III)-1-(2-pyridylazo)-2-naphthol complex on the surface of a hanging mercury drop electrode, followed by the reduction of the adsorbed complex during the cathodic scan. The peak potential was found to be –0.8 V vs. Ag/AgCl electrode and the reduction current of the adsorbed complex ions of platinum (II) or ruthenium (III) was measured by differential pulse cathodic stripping voltammetry. The optimum experimental conditions were: 1.5×10^–7 mol/l of 1-(2-pyridylazo)-2-naphthol solution of pH 9.3, preconcentration potential of –0.2 V, accumulation time of 3 min and pulse amplitude of 50 mV with 4 mV s^–1 scan rate in the presence of ethanol-water (30% v/v) — sodium sulphate (0.5 mol/l). Linear response up to 6.4 × 10^–8 and 5.1 × 10^–8 mol/l and a relative standard deviation (at 1.2×10^–8 mol/l) of 2.4 and 1.6% (n=5) for platinum (II) and ruthenium (III) respectively were obtained. The detection limits of platinum and ruthenium were 3.2×10^–10 and 4.1×10^–10 mol/l, respectively. The electronic spectra of the Pt(II) — PAN and Ru(III) — PAN complexes were measured at pH 9.3 and the stoichiometric ratios of the complexes formed were obtained by the molar ratio method. The effects of some interfering ions on the proposed procedure were critically investigated. The method was found suitable for the sub-microdetermination of ruthenium (IV) and platinum (IV) after their reduction to ruthenium (III) and platinum (II) with sulphur dioxide in acid media. The applicability of the method for the analysis of binary mixtures of ruthenium (III) and (IV) or platinum (II) and (IV) has also been carried out successfully. The method is simple, rapid, precise, and promising for the determination of the tested metal ions at micro-molar concentration level.     

Spectrophotometric determination of ruthenium after extraction of perruthenate with benzyltributylammonium chloride

A simple and convenient extractive spectrophotometric method for the determination of ruthenium has been developed. It is based on the oxidation of the different ruthenium (II, III or IV) species to perruthenate with potassium periodate at pH 7.8. The perruthenate is then extracted with benzyltributylammonium chloride in chloroform followed by direct spectrophotometric measurements at 342 and 380 nm. The optimum concentration range was found to be 0.1–5 mg l^–1, the standard deviation ±2.1%. The method has been successfully applied to the determination of ruthenium in organoruthenium compounds.     

Electrocatalytic Oxidation of Ethanol on Graphite Electrodes Coated with a Nafion Film with Incorporated Particles of Ruthenium or Its Complexes

The electrochemical behavior of ethanol on graphite electrodes with a Nafion film containing ruthenium as a crystalline metal deposit or a metal complex was compared. It was found that, in the oxidation of ethanol, aqua and phenanthroline complexes of ruthenium(III) incorporated in the Nafion film exhibit catalytic activity. A larger catalytic effect was observed at an electrode containing the Ru(phen) ₃ ³⁺ complex. A procedure is proposed for the voltammetric determination of ethanol at this electrode.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 603–609.Original Russian Text Copyright © 2005 by Shaidarova, Gedmina, Chelnokova, Budnikov.Presented at the VI All-Russian Conference (with International Participation) on Electrochemical Methods of Analysis (EMA-2004, Ufa, May 23–27, 2004).     

Sensitive spectrofluorimetric determination of ruthenium at nanotrace levels using 2-(α-pyridyl) thioquinaldinamide [PTQA]

A new spectrofluorimetric method for the determination of ruthenium with nonfluorescent 2-(α-pyridyl) thioquinaldinamide (PTQA) is described. The oxidative reaction of Ru(III) upon PTQA gives oxidised fluorescent product (λ_ex(max)=347 nm; λ_em(max)=486 nm). The sensitivity of the fluorescence reaction between ruthenium and PTQA is greatly increased in the presence of Fe (III). The reaction is carried out in the acidity range 0.01–0.075 M H₂SO₄. The influence of reaction variables is discussed. The range of linearity is 1–400 μg l⁻¹ Ru(III). The standard deviation and relative standard deviation of the developed method are ±1.210 μg l⁻¹ Ru (III) and 2.4%, respectively (for 11 replicate determinations of 50 μg l⁻¹ Ru (III)). The effect of interferences from other metal ions, anions and complexing agents was studied; the masking action is discussed. The developed method has been successfully tested over synthetic mixtures of various base metals and platinum group metals, synthetic mixtures corresponding to osmiridium, certified reference materials in spiked conditions and rock samples.     

The catalytic adsorptive stripping voltammetric determination of chromium with TTHA and nitrate

A sensitive voltammetric method is presented for the determination of trace amounts of total chromium (Cr(III) and Cr(VI)) in natural waters, employing the square wave mode. The method is based on the preconcentration of the Cr(III)-TTHA complex by adsorption at the HMDE at the potential of –1.0 V vs. Ag/AgCl. The adsorbed complex is then reduced producing a response with a peak potential of –1.29 V and the peak height of the Cr(III) reduction is measured. The catalytic action of the nitrate ions on the Cr(III)-TTHA reduction has been elucidated using cyclic voltammetry. The adsorption of chromium complexes at the HMDE was investigated using out-of-phase a.c. voltammetry and the potential range of adsorption was determined.Based on these investigations optimal conditions for the determination of the total chromium concentration in the range 155–2000 ng 1^–1 have been established. The determination limit is 15 ng 1^–1 and the RSD is 3.5% for chromium concentrations 200 ng 1^–1.The usefulness and wide scope of this method for reliable and highly sensitive chromium analysis down to the ultra trace levels existing in various types of natural waters is demonstrated by determinations of the total chromium content in lake, sea and rain water.     

Kinetic Spectrophotometric Method for the Determination of Rhodium by Its Catalytic Effect on the Oxidation of O-Toluidine Blue by Periodate in Micellar Media

A simple kinetic spectrophotometric method was developed for the determination of ultra trace amounts of Rh(III). The method is based on the catalytic effect of rhodium(III) on the oxidation of o-Toluidine blue by periodate in micellar media. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of o-Toluidine blue at 628 nm with a fixed-time method. The decrease in the absorbance of o-Toluidine blue is proportional to the concentration of Rh(III) in the concentration range 1.0–400.0 ng/mL, with a fixed time of 0.5–4.5 min from initiation of the reaction. The limit of detection is 0.2 ng/mL Rh(III). The relative standard deviation for the determination of 0.020 and 0.100 g/mL Rh(III) was 2.2 and 1.5%, respectively. The method was applied to the determination of rhodium in water.     

Indirect kinetic determination of As(III) based on its accelerating effect on the Os(VIII)-catalysed reaction between iodide and bromate in a micellar medium

Summary An indirect kinetic-photometric method for the determination of As(III) over the range 7–300 ng ml^–1 is proposed. It is based on the accelerating effect of this ion on the Os(VIII)-catalysed reaction between iodide and bromate, which is monitored via the triiodide formed. Arsenic(III) acts as an accelerator only in a very rapid initial step of the reaction and the rate processes occurring in the system after this step do not depend directly on the As(III) concentration. Therefore, the contribution of this ion to the reaction must be measured after its accelerating effect has cancelled. Dodecyltrimethyl-ammonium bromide (DTAB) micelles accelerate the reaction, and hence increase the sensitivity and selectivity of the determination of As(III) compared to reactions taking place in an aqueous medium. Some observations on the mechanism via which DTAB acts on the reaction are reported. The role of micellar media in catalytic kinetic methods is discussed.     

Kinetic ultramicrodetermination of chromium(III) and osmium(VIII) based on their accelerating effect on the periodate-arsenite reaction

Summary A spectrophotometric kinetic method is described for the ultramicrodetermination of chromium (III) and osmium (VIII) based on their promoting and catalytic effect respectively on the periodate — arsenite reaction. For chromium(III) determination the decrease in absorbance within a fixed period of time is related directly to the chromium concentration. For osmium (VIII) determination the time required for the reaction to consume a fixed amount of periodate is measured automatically and related directly to the osmium concentration. Ultramicroamounts of chromium(III) in the 10^–6–10^–5 M level and of osmium(VIII) in the 10^–8–10^–7 M level were determined with a mean error of about 2%. The method has been applied to the determination of chromium in chrome ores.

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Zusammenfassung Eine kinetische Methode zur Ultramikrobestimmung von Chrom(III) und Osmium(VIII) auf der Grundlage ihrer beschleunigenden bzw. katalytischen Wirkung auf die Perjodat-Arsenit-Reaktion wurde beschrieben. Für Chrom dient die Abnahme der Extinktion innerhalb einer bestimmten Zeitspanne als Maß der Konzentration. Bei der Bestimmung von Osmium(VIII) wird die Zeit für den Verbrauch einer bestimmten Menge Perjodat automatisch gemessen. Sie entspricht direkt der Osmiumkonzentration. Ultramikromengen Cr(III) in der Größenordnung 10^–6–10^–5 M und Os(VIII) in der Größenordnung 10^–8–10^–7 M sind mit einem Fehler von ungefähr 2% bestimmbar. Die Methode wurde zur Chrombestimmung in Erzen angewendet.

     

Highly sensitive catalytic spectrophotometric determination of ruthenium

A new and highly sensitive catalytic kinetic method (CKM) for the determination of ruthenium(III) has been established based on its catalytic effect on the oxidation of l-phenylalanine (l-Pheala) by KMnO(4) in highly alkaline medium. The reaction has been followed spectrophotometrically by measuring the decrease in the absorbance at 526nm. The proposed CKM is based on the fixed time procedure under optimum reaction conditions. It relies on the linear relationship where the change in the absorbance (DeltaA(t)) versus added Ru(III) amounts in the range of 0.101-2.526ngml(-1) is plotted. Under the optimum conditions, the sensitivity of the proposed method, i.e. the limit of detection corresponding to 5min is 0.08ngml(-1), and decreases with increased time of analysis. The method is featured with good accuracy and reproducibility for ruthenium(III) determination. The ruthenium(III) has also been determined in presence of several interfering and non-interfering cations, anions and polyaminocarboxylates. No foreign ions interfered in the determination ruthenium(III) up to 20-fold higher concentration of foreign ions. In addition to standard solutions analysis, this method was successfully applied for the quantitative determination of ruthenium(III) in drinking water samples. The method is highly sensitive, selective and very stable. A review of recently published catalytic spectrophotometric methods for the determination of ruthenium(III) has also been presented for comparison.     

The analysis of ruthenium catalysts by photon-induced X-ray fluorescence using a microcomputer for data acquisition and analysis

An improved method for the determination of ruthenium in catalytic materials based on a relative fluorescence ratio factor is presented. This method employs a thin-film technique and an internal standard technique to minimize absorption and enchancement effects. The samples and standards were fluorescent with a¹⁰⁹Cd (7 mCi) annular source for 200 seconds and the data were collected and analyzed with an Apple II+ micro computer. Precision (total variation) for typical ruthenium catalysts in the range of 1–5% ruthenium was about 2%. Finally, the concentration of ruthenium in six commercial catalysts was determined for both alumina and carbon supports.Parts of this work have been funded by an international program between CONICIT (Venezuela) and NSF (United States of America).     

Chemiluminescent stages of Belousov-Zhabotinskii reactions in systems with ruthenium complexes

The autooscillatory catalytic oxidation of malonic acid (MA) by bromate (the Belousov-Zhabotinskii reaction) in the presence of the trisbipyridyl complexes of ruthenium Ru(II, III) is accompanied by bright chemiluminescence (CL) which appears during the reduction of the Ru(III) by the active intermediate products (organic radicals). It was shown that the chemiluminescence results from interaction of the Ru(III) not with MA radicals formed at the first stage of its oxidation but with stronger reducing agents, i.e., the radicals of hydroxymalonic acid and, probably, the OCOOH and HO₂ radicals. The main paths leading to the formation and consumption of these radicals are reactions involving the bromate. A simplified scheme is presented for the process leading to the appearance of chemiluminescence in the MABrO₃ ^–-Ce(III, III) and MA-BrO₃ ^–-Ce(III, IV)-Ru(II, III) systems. It confirms the experimental relatinships between the maximum intensity of the chemiluminescence and the concentrations of the reagents.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 5, pp. 566–573, September–October, 1990.     

Photometric determination of palladium with 3-nitroso-2,6-pyridinediol

Summary A highly sensitive and selective photometric method has been developed for the determination of palladium. The method is based on the yellow complex (absorption maximum-430 run) formed when palladium and 3-nitroso-2,6-pyridinediol are heated together in 0.1M perchloric acid. The reaction ratio is 21 reagent to palladium. The molar absorptivity of the yellow complex is 2.6 · 10⁴ liter mole^–1 cm^–1. Only platinum (IV), ruthenium (III), and iron(III) seriously interfere among the common and platinum metals.

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Zusammenfassung Eine sehr empfindliche und selektive photometrische Methode zur Palladiumbestimmung wurde ausgearbeitet. Sie beruht auf dem gelben Komplex (Absorptionsmaximum bei 430 nm), der sich beim Erwärmen aus Palladium und 3-Nitroso-2,6-pyridindiol in 0,1-n Perchlorsäure bildet. Reagens und Metallion reagieren im Verhältnis 21. Die molare Absorption beträgt 2,6 · 10⁴ 1 mol^–1 cm^–1. Nur Platin(IV), Ruthenium(III) und Eisen(III) stören die Bestimmung.

     

Catalytic kinetic determination of ultratrace amounts of ruthenium(III) based on the oxidation of benzylamine by alkaline hexacyanoferrate(III)

A kinetic method is proposed for the determination of ruthenium(III) by means of its catalytic effect on the oxidation of benzylamine by hexacyanoferrate(III) in alkaline medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance of hexacyanoferrate(III) at 420 nm. Under the optimum experimental conditions ruthenium(III) can be determined in the range 10-121 ng/ml with an average error of 1.7% and maximum relative standard deviation of 1.3%. The influence of many potential interferents has been examined and the method has been tested for determination of ruthenium(III) in synthetic mixtures. The method is convenient, reliable and rapid.     

Spectrophotometric determination of iron in aluminium metal and some non-ferrous alloys

A new, sensitive and selective spectrophotometric method is suggested for the determination of traces of iron(III) based on complex formation with hematoxylin in presence of cetyltrimethylammonium bromide (CTAB). Addition of CTAB shifted the absorption maximum of the iron-hematoxylin complex from 630 to 640 nm and increased its molar absorptivity from 9.88 × 10⁴ to 1.16 × 10⁵ 1·mol^–1·cm^–1. The method adhered to Beer's law up to 0.4 and 0.2 g/ml of iron in presence and absence of CTAB, respectively. The corresponding values of Sandell's sensitivity were 0.5 and 0.6 ng·cm^–2. The effect of reagent and surfactant concentrations, pH and standing time were investigated. EDTA, tartrate and sodium fluoride were used as masking agents for most of the interfering ions. The method was successfully used for the determination of iron in aluminium metal and some non-ferrous alloys.     

Simultaneous determination of uranium(IV) and iron(II) with a stopped-flow inductive kinetic spectrophotometric method

A kinetic method for simultaneous determination of multielements is proposed, and a procedure for simultaneous determination of uranium(VI) and iron(II) is established based on their inductive effect on the chromium(VI)-iodide redox reaction in weak acidic medium. The reaction was monitored with the stopped-flow spectrophotometric technique by using I ₃ ^– -starch complex as indicator. The calibration graphs are linear for 0–3.6 g.cm^–3 U(IV), and 0–2.5 g.cm^–3 Fe(II), respectively. Most foreign ions, except for V(IV), Sb(III), do not interfere with the determination.     

The catalytic adsorptive stripping voltammetric determination of chromium with DTPA and nitrate

Summary The catalytic adsorptive stripping voltammetric determination of chromium using diethylenetriaminepentaacetic acid (DTPA) is only possible when chromium(III) is preliminarily oxidized to chromium(VI) which can be accomplished by UV-irradiation of the oxygen saturated solution at pH 6.0–7.0. A chromium(III)-chromium(VI) speciation can be performed in the range 10^–10 mol/l upto 10^–6 mol/l employing the coprecipitation of chromium(III) with Al(OH)₃. The interference of other metal ions was also studied.     

Kinetic–Spectrophotometric Determination of Trace Silver(I) Using Its Catalytic Effect on the Oxidation Reaction of Fuchsin by Peroxodisulfate in the Presence of 1,10-Phenanthroline As an Activator

A kinetic spectrophotometric method for the determination of trace amounts of Ag(I) in the range of 2–20 ng mL^–1 is reported. The method is based on the catalytic effect of Ag(I) on the oxidation reaction of fuschin by potassium peroxodisulfate in the presence of 1,10-phenanthroline as an activator at pH = 5. The reaction is followed spectrophotometrically by measuring the change in absorbance (A) at 544 nm using a fixed time method (6 min). The reaction variables were optimized in order to achieve the highest sensitivity. The 3s criterion detection limit was 0.7 ng mL^–1, and the relative standard deviation for ten replicate measurements of 16 ng mL^–1 of Ag(I) was 0.95% (n = 10). The method was successfully applied to the determination of silver in expired black and white photographic films and results showed good agreements with those obtained by atomic absorption spectrometry.     

Flow injection catalytic determination of ruthenium with spectrophotometric detection

A new flow injection catalytic method was described for the determination of ruthenium(III) based on its catalytic effect on the oxidation of brilliant cresyl blue (BCB) by periodate in acidic media. The reaction was followed spectrophotometrically by measuring the absorbance of the dye at 635 nm. Under optimum conditions, ruthenium can be determined in the range of 1.0-100.0 ng ml(-1) with a relative standard deviation of 1.1% and with a limit of detection of 0.70 ng ml(-1). The influence of reagent and manifold variables were studied and optimized. The method was tested for the determination of ruthenium(III) in some synthetic mixtures.     

Catalytic Determination of Trace Amounts of Iridium As Chloride Complexes

A procedure was developed for the determination of iridium as chloride complexes by its catalytic action on the oxidation reaction of Sulfarsazene with potassium periodate at pH 5.6. The analytical range was 1 × 10^–5–1 × 10^–3 g/mL iridium. The accuracy of the procedure developed was confirmed in the determination of iridium in model solutions by the standard addition method. The relative standard deviation did not exceed 6%.     

Application ofo-Hydroxyphenylfluorone as a Fluorogenic Indicator to the Determination of Hydrogen Peroxide and Oxidase Substrates Based on the Catalytic Effect of Hemin

A highly sensitive fluorescence quenching method has been developed for selective determination of hydrogen peroxide based on the catalytic effect of hemin on theo-hydroxyphenylfluorone (a new fluorogenic substrate) and hydrogen peroxide system. Under optimum conditions, the calibration graph was linear over the range 0–1.0 × 10⁻⁶mol/liter hydrogen peroxide, with a limit of detection of 8.0 × 10⁻⁹mol/liter in a 10-min reaction period. It can easily be incorporated into the determination of biochemical substances that produce hydrogen peroxide under catalytic oxidation by their oxidase. This possibility has been tested for the determination of glucose in human sera as an example.