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.

     

Voltammetric trace determination of ubiquinones at mercury electrodes

Summary Voltammetric methods were developed for the determination of ubiquinones on the basis of their adsorption and redox behaviour at mercury electrodes. Linear calibration plots were obtained in the concentration range between 10^–4 mol/l and 2.3·10^–5 mol/l from differential pulse voltammetric measurements under experimental conditions avoiding significant adsorption of the analyte. A remarkable decrease of the detection limit down to 10^–7 mol/l was achieved with the help of adsorptive accumulation of ubiquinone molecules at the mercury electrode followed by differential pulse detection. The resulting non-linear calibration plot was explained with a model, which takes into account both adsorption and diffusion of the analyte.     

Extraction-spectrophotometric determination of uranium(VI) with PAR and N-octylacetamide

A new and simple method for selective spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol (PAR) and N-octylacetamide into benzene over pH 7.0–9.0 is described. The molar absorptivity of the complex with 9 different amides is in the range of (0.40–3.2)·10⁴ 1·mol^–1·cm^–1 at the absorption maximum. Out of these, the most sensitive compound N-octylacetamide (OAA) was chosen for detailed studies in the present investigation. The detection limit of the method is 0.008 g U·ml^–1. The system obeys Beer's law in the range of 0–5 g U·ml^–1. The method is free from interferences of most of the common metal ions except vanadium(V) and copper(II), which are masked by proper masking agents. The composition of the complex is determined by curve-fitting method. The method has been applied for the recovery of the metal from rock samples and synthetic mixtures.     

A gas-jet system for the study of short-lived,light fission products

A selective method for the solvent extraction and spectrophotometric determination of uranium(VI) is described. Uranium can be extracted into chloroform at pH 6.0 with N-m-chlorophenyl-2-theno-hydroxamic acid (N-m-CPTHA) and determined by spectrophotometry using 1-(2-pyridylazo)-2-naphthol (PAN). The molar absorptivity is 1.50·10⁴ 1·mol^–1·cm^–1 at 560 nm. The system obeys Beer's law within the range 0.95–20.00 ppm of uranium. Alternatively, a back-extraction procedure was also developed in which uranium is back-extracted by nitric acid and estimated spectrophotometrically using Arsenazo III. The molar absorptivity is 2.0·10⁴ 1·mol^–1·cm^–1 at 665 nm. The parameters concerning the optimum conditions for the analytical method are discussed. The proposed method is applied precisely for the determination of uranium in rock and sea water samples.     

Kinetic Determination of Mercury(II) at Trace Level from Its Catalytic Effect on a Ligand Substitution Process

A catalytic kinetic method (CKM) is presented for the determination of mercury(II) based on its catalytic effect on the rate of substitution of N-methylpyrazinium ion (Mpz⁺) onto hexacyanoferrate(II). The progress of the reaction was monitored spectrophotometrically at 655 nm by registering the increase in absorbance of the product [Fe(CN)₅(Mpz]²⁻ under the reaction conditions: 5 × 10⁻³ mol L⁻¹ [Fe(CN)₆]⁴⁻), 5 × 10⁻⁵ mol L⁻¹ [Mpz⁺], T = 25.0 ± 0.1°C, pH 5.00 ± 0.02 and ionic strength, I = 0.1 mol L⁻¹ (KNO₃). Quantitative rate data at specified experimental conditions showed a linear dependence of the absorbance after fixed time A _t on the concentration of mercury(II) catalyst in the range 20.06–702.1 ng mL⁻¹. The maximum relative standard deviations and percentage errors for the determination of mercury(II) in the range of 20.06–200.6 ng mL⁻¹ were calculated to be 1.7 and 2.7% respectively. The detection limit was found to be 7.2 ng mL⁻¹ of mercury(II). Accuracy (expressed in terms of recoveries) was in the range of 98–103%. Figures of merit and interference due to many cations and anions was investigated and discussed. The applicability of the method was demonstrated by determining the mercury(II) in different synthetic samples and confirming the results using atomic absorption spectrophotometry. The proposed method allowed determination of mercury(II) in the range 20.06–702.1 ng mL⁻¹ with very good selectivity and an output of 30 samples h⁻¹.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 654–661.Original English Text Copyright © 2005 by Surendra Prasad.This article was submitted by the author in English.     

Determination of nanomolar levels of guanine by differential-pulse adsorptive cathodic stripping voltammetry of its copper(II) complex

Guanine is determined at the 5.0×10^–10 –2.0×10^–7 mol/l level by differential-pulse adsorptive stripping voltammetry at a hanging mercury drop electrode using the reduction peak of its copper (II) complex at –0.21 V vs. Ag-AgCl electrode. The optimum analytical conditions were found to be Britton-Robinson buffer solution (pH 4.8), an accumulation potential of 0.0 V and an accumulation time of 3 min. Under these conditions, the detection limit is 5.0×10^–10 mol/l and the relative standard deviation 2.6% for 1.0×10^–7 mol/l guanine. The method is compared with the previous voltammetric methods. The presence of some purine derivatives does not interfere.     

Rapid Determination of Mercury in Water by Stripping Voltammetry at a Gold-Modified Carbon Electrode

A procedure was developed for determining mercury in natural water by stripping voltammetry on a gold-modified carbon electrode. The concentration dependence of the anodic stripping current of mercury is linear in the range 0.02–5 g/L Hg(II). The interference of Fe(III), Cu(II), Cl^–, Br^–, I^–, and F^– ions with the determination of mercury was studied. Ozonation was used for rapid sample preparation. The detection limit for mercury was 0.02 g/L at an electrolysis time of 5 min.     

Spectrophotometric determination of mercury with thiocyanate and Rhodamine B

Summary Mercury(II) in the presence of a large excess of thiocyanate forms a violet colour with Rhodamine B. The complex formed can be stabilized by addition of poly(vinyl alcohol), and forms the basis for a spectrophotometric method for determination of trace amounts of mercury. The calibration graph for measurement at 610 nm is linear in the range 1–15g of mercury per 25 ml, with a molar absorptivity of 1.1×10⁵l· mole^–1·cm·. The effect of foreign ions has been studied and the method can be applied to the determination of mercury in air with reliable analytical results.

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Spektrophotometrische Bestimmung von Quecksilber mit Rhodanid und Rhodamin B

Zusammenfassung In Gegenwart eines großen Überschusses von Rhodanid bildet Hg(II) mit Rhodamin B eine violette Färbung. Durch Zusatz von Polyvinylalkohol kann dieser Komplex stabilisiert werden und bietet somit die Grundlage für die spektrophotometrische Bestimmung von Hg-Spuren. Die Eichkurve für die Messung bei 610 nm verläuft für 1–15g Hg/25 ml linear. Die molare Absorptivität beträgt 1,1×10⁵ l·mol^–1·cm^–1. Die Fremdionenwirkung wurde untersucht. Das Verfahren kann zur Hg-Bestimmung in Luft verwendet werden.

     

Polarographic study of a triazolobenzodiazepine: Estazolam

Summary The polarographic behaviour of 8-chloro-6-phenyl-4H-s-triazolo(4,3-a)-(1,4)-benzodiazepine (estazolam) was studied in the pH range 3–10. The reduction process is irreversible and the current is diffusion-controlled. The linear relationship between current and estazolam concentration permits its polarographic determination in the range 3.4·10^–7–1.0·10^–4 M. The detection limit was 1.7·10^–7 M. The reproducibility of the method in terms of its relative standard deviation was 1.00% and 1.14% using ten determinations at the 2.4·10^–5 M and 3.4·10^–6 M levels respectively.

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Polarographische Untersuchung des Triazolbenzodiazepins Estazolam

     

Electrochemical properties of a new cytostatic agent: 2-Formylpyridine thiosemicarbazone

Summary The electrochemical characteristics of 2-formylpyridine thiosemicarbazone (2-FPTS) have been studied by direct current, alternating current, and differential pulse polarography and cyclic voltammetry at a mercury electrode. This new cytostatic agent is reduced in a two-electron irreversible step at the nitrogen double bond of the side chain, in the pH range 0.2–12. A double anodic wave very close to the oxidation wave of mercury, corresponding to the formation of an organo-mercury compound, develops in neutral and alkaline media. These different electrochemical reactions are complicated by adsorption. In alkaline media, the carbon-nitrogen double bond reduction current decreases progressively with increasing pH due to formation of an electrochemically inactive species. Finally, a catalytic reduction wave of protons is developed in neutral solutions. Quantitative determination of the compound was possible in the range 1×10^–7 to 1×10^–3 M, using the diffusion controlled reduction wave at pH 7. The qualitative detection limit is 2×10^–8 M (4 ng/ml).

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Elektrochemische Eigenschaften einer neuen cytostatischen Substanz: 2-Formylpyridin-thiosemicarbazon

Zusammenfassung Die elektrochemischen Eigenschaften von 2-Formylpyridin-thiosemicarbazon wurden mit Hilfe der Gleichstrom-, Wechselstrom- und Differentialpuls-Polarographie sowie der cyclischen Voltammetrie an der Hg-Elektrode untersucht. Die neue cytostatische Substanz wird in einer irreversiblen Zweielektronen-Stufe an der Stickstoff-Kohlenstoff-Doppelbindung der Seitenkette reduziert (pH-Bereich 0,212). In neutralen und alkalischem Medium entwickelt sich eine anodische Doppelstufe dicht bei der Oxidationsstufe des Quecksilbers, entsprechend der Bildung einer quecksilberorganischen Verbindung. Diese elektrochemischen Reaktionen werden durch Adsorptionsvorgange verkompliziert. In alkalischem Medium nimmt der Reduktionsstrom der Kohlenstoff-Stickstoff-Doppelbindung mit zunehmendem pH ab, was der Bildung einer elektrochemisch inaktiven Substanz zugeschrieben wird. In neutraler Lösung wird eine katalytische protonische Reduktionsstufe gebildet. Die quantitative Bestimmung war im Bereich von 1·10^–7 bis 1·10^–3 M möglich, wobei die diffusionskontrollierte Reduktionsstufe bei pH 7 benutzt wurde. Die qualitative Nachweisgrenze liegt bei 2·10^–8 M (4 ng/ml).

     

Spectrophotometric determination of iron after separation of its 9,10-phenanthrenequinone monoximate on microcrystalline naphthalene

A sensitive and selective spectrophotometric method has been developed for the determination of iron as Fe(II) or Fe(III) using 9,10-phenanthrenequinone monoxime (PQM) as the complexing agent. Fe(II) and Fe(III) react with PQM to form coloured water insoluble complexes which can be adsorbed on microcrystalline naphthalene in the pH ranges 3.7–6.2 and 2.0–8.4, respectively. The solid mass consisting of the metal complex and naphthalene is dissolved in DMF and the metal determined spectrophotometrically by measuring the absorbances Fe(II) at 745 nm and Fe(III) at 425 nm. Beer's law is obeyed over the concentration range 0.5–20.0 g of iron(II) and 20–170.0 g of Fe(III) in 10 ml of DMF solution. The molar absorptivities are 1.333 × 10⁴ 1 · mole^–1 · cm^–1 for Fe(II) and 2.428 × 10³1· mole^–1 · cm^–1 for Fe(III). The precision of determination is better than 1%. The interference of various ions has been studied and the method has been employed for the determination of iron in various standard reference alloys, bears, wines, ferrous gluconate, human hair and environmental samples.     

One electron oxidation of Ni(II)-iminodiacetate by carbonate radical

Reactions of carbonate radical (CO₃ ^–), generated by photolysis or by radiolysis of a carbonate solution with nickel(II)-iminodiacetate (Ni(II)IDA) were studied at pH 10.5 and ionic strength (I)==0.2 mol·dm^–3. The stable product arising from the ligand degradation in the complex is mainly glyxalic acid. Time-resolved spectroscopy and transient kinetics were studied using flash photolysis. From the kinetic data it was suggested that the carbonate radical initially reacts with Ni(III)IDA with a rate constant (2.4±0.4)·10⁶ dm³·mol^–1·s^–1 to form a Ni(II)IDA species which, however, undergoes a first-order transformation (k=2.7·10²·s^–1) to give a radical intermediate of the type Ni(II)RNHCHCO ₂ ^– ) which rapidly forms an adduct containing a Ni–C bond. This adduct decays very slowly to give rise to glyoxalic acid. From a consideration of equilibrium between Ni(II)IDA and Ni(III)IDA, the one electron reduction potential for the Ni(III)IDA/Ni(II)IDA couple was determined to be 1.467 V.     

Photometric titrations of mercury(II) based on UV-absorption of mercury(II)-complexes

Summary A method is described for the complexometric determination of traces of mercury(II) with EDTA, EGTA and DTPA, with photometric endpoint indication. Titrations with EDTA and EGTA appeared to be possible only if acetylacetone was added. The wavelength used in that case was 275 nm. With DTPA a direct titration is possible at 260 nm. At p_H 2 determinations of 2·10^–5 M mercury(II) are possible with good accuracy.

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Zusammenfassung Eine komplexometrische Bestimmung von Spuren Quecksilber(II) mit ÄDTA, ÄGTA und DTPA wurde beschrieben. Die Endpunktanzeige erfolgte photometrisch. Titrationen mit ÄDTA und ÄGTA waren nur möglich in Anwesenheit von Acetylaceton. In diesem Fall war die verwendete Wellenlänge 275 nm. Mit DTPA sind auch direkte Titrationen möglich bei 260 nm. Bei p_H 2 sind Analysen von 2·10^–5-m Lösungen mit guter Genauigkeit durchführbar.

     

Interaction of pectin substances with copper,mercury, zinc,and cadmium salts

The interaction of the sage, mint, apple, and ginseng pectins, isolated from tissue culture wastes and purified with copper, mercury, zinc, and cadmium salts, has been studied by the amperometric method with two metal indicator electrodes. The optimum conditions of titration have been determined: pH 3.5–5.0; concentration of pectin substances 5·10^–5-1·10^–3 g/ml of solution. It has been established by graphical and mathematical methods that the interaction is accompanied by the formation of compounds with a ratio of the carboxy groups of pectins to the metal cation of two. The IR spectra of sage pectin and of copper and mercury pectinates are given.M. V. Frunze, Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 171–175, March–April, 1988.     

Comparison study between indirect photometric and direct conductivity detection for anion exchange chromatography using naphthalenesulfonate derivatives as mobile phases

Summary Indirect photometric and unsuppressed direct conductivity detection modes are examined using naphthalene mono-, di-, and tri-sulfonate as mobile phases for the separation of several anions such as F^–, Cl^–, NO₂ ^–, Br^–, NO₃ ^–, SO₄=,I^–, and SCN^– using a commercial anion exchange column. With all three mobile phases, conductivity detection shows better sensitivities and detection limits than indirect photometry. Conductivity detection is 5 to 16 times more sensitive than indirect photometry for all analytes. Detection limits achieved using these mobile phases are, for example, 0.04 ng and 0.1 ng for chloride ion with conductivity and indirect photometry, respectively. Both detection modes give wide linear ranges extending from at least 100 ppm to the detection limit of each anion which is generally about 0.02 ppm. Sulfur oxide anions such as dithionate and tetrathionate are separated using flow programming with naphthalenetrisulfonate as the mobile phase in less than 20 minutes. With both detection modes, desired chromatographic performance of these three eluents is achieved without pH adjustment of the mobile phase.     

Polarographic determination of uranium(VI) after salting-out extraction as 8-quinolinolate in acetonitrile

Summary Uranium(VI) can be extracted as its 8-quinolinolate into acetonitrile by means of salting-out with ammonium and sodium acetates, respectively; the metal oxinates extracted give a well-defined dc polarogram with E _1/2=–0.80V and a sharp square wave (sw) polarogram with E _p=–0.96V in the extract. The dc wave height and the sw peak current are directly proportional to the uranium(VI) concentration in the range of 6.0×10^–6 to 4.0×10^–4M at pH 6.7–10.0 and 8.0×10^–7 to 2.8×10^–5M at pH 10.5–11.0, respectively. A number of ions do not interfere in the presence of EDTA.

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Polarographische Bestimmung von Uran(VI) nach Aussalz-Extraktion als 8-Hydroxychinolat mit Acetonitril

Zusammenfassung Uran(VI) kann durch Aussalzen mit Ammonium- bzw. Natriumacetat als Oxinat mit Acetonitril extrahiert werden. Das extrahierte Oxinat ergibt ein gut ausgebildetes Gleichstrompolarogramm mit E _1/2=–0,80 V bzw. ein scharfes square-wave-Polarogramm mit E _p=–0,96 V. Die Gleichstrom-Stufenhöhe bzw. der square-wave-Peakstrom sind der U(VI)-Konzentration im Bereich 6,0·10^–6-4,0· 10^–4M (pH 6,7–10,0) bzw. 8,0·10^–7-2,8·10 ^–5M (pH 10,5–11,0) direkt proportional. Durch Zusatz von EDTA kann eine Reihe von Störungen ausgeschaltet werden.

     

Direct and Derivative Spectrophotometric Determination of Thorium with 2,4-dihydroxybenzaldehyde Isonicotinoyl Hydrazone

A simple and sensitive spectrophotometric method is developed for the determination of throium in aqueous medium. The metal ion forms yellow coloured complex with 2,4-dihydroxybenzaldehyde isonicotinoyl hydrazone (2,4-DHBINH) in the pH range 2.0–8.0. The complex shows an absorption maximum at 390 nm. The absorbance of the complex is maximum at pH 5.5 Beer's law is obeyed in the range 0.30–7.00 g/ml of thorium(IV). The molar absorptivity and the Sandell's sensitivity of the method are 2.20· 10⁴ l·mol^–1·cm^–1 and 0.0106 g/cm^–2, respectively. The interference of various ions was studied. The composition of the complex is 1:1 {Th(IV) : 2,4-DHBINH}. The first derivative spectrum of the complex shows a zero cross at 391.2 nm and maximum amplitude at 415 nm. Thus a sensitive derivative spectrophotometric method for the determination of Th(IV) is proposed.     

Comparison of Different Sorbents for Solid-Phase Extraction of Phenoxyalkanoic Acid Herbicides

An HPLC procedure for determination of phenoxyalkanoic acid herbicides in water samples is proposed. The analytical column Phenomenex C18(2) Luna 5 µm and UV detection at 225 nm were applied. Baseline resolution was achieved in isocratic mode with a mobile phase consisting of acetonitrile/acetic acid (40/60, v/v), adjusted to pH 2.5. SPE sorbents – C₁₈ BondElut, phenyl-silica, LiChrolut SAX and polymeric sorbents – were compared for isolation and preconcentration of 6 phenoxyalkanoic acid herbicides. Higher (above 95%) and more reproducible recoveries were obtained with polymeric and phenyl-silica sorbents using pure methanol for elution. The method was tested for river water samples with the limit of detection in the range of 2–3 µg L⁻¹ (for 50 mL sample) and a reproducibility of 5% RSD.     

Separation of fluoride ion by extraction with triphenyltin chloride. Application for NAA of fluorine by means of 14-MeV neutrons

The separation of fluoride by extraction with toluene solution of triphenyltin chloride has been studied. Quantitative isolation of fluoride from solutions with a wide acidity range (pH 4.0–11.5) has been established. It is suggested that interferences by Ca, Mg, Fe, and Al can be avoided by masking these elements using sulfate and hydroxyde ions. Interference by phosphate ions can be overcome in a similar fashion. The halogenated species can be masked by mercury nitrate. Detection limit for fluorine determination is about 3 g for a neutron generator flux of 2·11¹¹ n·cm^–1·s^–1. A method for fluorine assay in water using a neutron generator with a detection limit of 1 ppm has been developed.     

Voltammetric study of the interaction of lomefloxacin (LMF)–Mg(II) complex with DNA and its analytical application

The voltammetric behavior of the LMF-Mg(II) complex with DNA at a mercury electrode is reported for the first time. In NH₃–NH₄Cl buffer (pH=9.10), the adsorption phenomena of the LMF–Mg(II) complex were observed by linear sweep voltammetry. The mechanism of the electrode reaction was found to be a reduction of LMF in the complex, and the composition of the LMF–Mg(II) complex is 2:1. In the presence of calf thymus DNA (ctDNA), the peak current of LMF–Mg(II) complex decreased considerably, and a new well-defined adsorptive reduction peak appeared at −1.63 V (vs. SCE). The electrochemical kinetic parameters and the binding number of LMF–Mg(II) with ctDNA were also obtained. Moreover, the new peak currents of LMF–Mg(II)–DNA system increased linearly correlated to the concentration of DNA in the 4.00×10⁻⁷–2.60×10⁻⁶ g ml⁻¹ range when the concentrations of LMF–Mg(II) complex was fixed at 5.00×10⁻⁶ mol l⁻¹, with the detection limits of 2.33×10⁻⁷ g ml⁻¹. An electrostatic interaction was suggested by electrochemical method.