Kinetic-potentiometric determination of copper in real samples with a new antimony(V) ion-selective electrode

Summary A sensitive and selective kinetic method for the determination of copper is proposed. It is based on the catalytic effect of copper on the reaction between hexachloroantimonate(V) and hydroxylamine at pH 4.4 (acetic-acetate buffer). The rate of the reaction is potentiometrically monitored with a new antimony(V) ion-selective electrode using 1,2,4,6-tetraphenyl-pyridinium hexachloroantimonate(V) as electroactive material in a poly-(vinyl chloride) membrane. The proposed method allows the determination of copper(II) concentrations in the 5–510 ng ml^–1 range, with a variation coefficient of 3.5%. The method has satisfactorily been applied to a variety of real samples.     

Selective kinetic spectrophotometric determination of copper at nanograms per milliliter level

A sensitive and selective kinetic method is proposed for the determination of nanogram amounts of copper. The method is based on the catalytic effect of copper on the reduction of Ponceau S by sodium sulfide in an alkaline media. The rate of the reaction is monitored spectrophotometrically at 560 nm. The method allows determination of copper concentrations in the range 2-400 ng ml(-1) with a relative standard deviation of approximately 2%. The proposed method, which is highly selective to copper, has been applied satisfactory to its determination in real samples.     

Near-Infrared Fluorimetric Determination of Copper(Ⅱ) Ions Using CdHgTe Nanorods as Probe

Stable water‐soluble CdHgTe nanorods with an emission wavelength at 722 nm, obtained by doping Hg²⁺ into CdTe nanorods, has been used as a near‐infrared region (NIR) probe to investigate their interaction with copper(II) ions. A new fluorimetric method for the determination of copper(II) ions has been developed based on the quenching effect of copper(II) ions on the emission of CdHgTe nanorods. The mechanism studies show that an effective electron transfer from nanorods to the copper(II) ions occurred based on the coordination reaction between copper(II) ions and the carboxyl groups on the nanorods surface, which could be responsible for the emission quenching of CdHgTe nanorods. Under optimum conditions, the linear range of the calibration curve for the determination of Cu²⁺ is from 8.0×10^?9 to 1.0×10^?6 mol/L and the detection limit is 2.0×10^?9 mol/L. Owing to low background interference of NIR measurement, the proposed method displays relative high sensitivity and selectivity. Especially, some physiologically important cations almost do not interfere with the determination of Cu²⁺. The proposed method was also applied to the determination of trace Cu²⁺ in real aqueous samples with satisfactory results.     

Determination of ultramicroquantities of Au(III) by its catalytic effect on 4-hydroxyl coumarone oxidation with potassium permanganate

A simple and fast kinetic method is based on the oxidation of 4-OH coumarone using KMnO₄ and the determination of ultramicroamounts of Au(III) by its catalytic effect on this reaction. The sensitivity of the method is 25 ng/mL. The relative error ranges between 9.20–3.90% for the concentration interval 5 × 10⁻⁸–2 × 10⁻⁷ g/mL. The selectivity of the method is very good, and the effect of foreign ions is investigated. The proposed approach has been applied to the determination of traces of Au(III) in copper ore. The text was submitted by the authors in English.     

Stopped-flow injection determination of copper(II) at the ng ml−1 level

A stopped-flow injection method for the determination of copper(II) in the range 0.2–300 ng ml^?1 is proposed, based on the catalytic effect of this ion on the 2,2'-dipyridylketone hydrazone/hydrogen peroxide reaction. The oxidation product shows an intense blue fluorescence that is monitored at λ_ex = 350 nm, λ_em = 427 nm. The sampling rate (72 h^?1), r.s.d. (1.4%) and the lack of interference from most foreign ions, allowed application of the method to the determination of copper in foods and blood serum.     

Flow-injection determination of copper(II) based on its catalysis on the redox reaction of cysteine with iron(III) in the presence of 1,10-phenanthroline

A redox reaction of cysteine with iron(III) proceeds slowly in the presence of 1,10-phenanthroline (phen). However, this reaction is accelerated in the presence of copper(II) as a catalyst, producing an iron(II)-phen complex (lambda(max)=510 nm). A sensitive spectrophotometric flow-injection method is proposed for the determination of copper(II) based on its catalytic action on this redox reaction. The dynamic range was 0.1-10 ng ml(-1) of copper(II) with a relative standard deviation of 1.0% (n=10) for 1.0 ng ml(-1) of copper(II) at a sampling rate of 30 h(-1). The detection limit (S/N=3) is 0.04 ng ml(-1). The proposed method was successfully applied to the determination of copper in river water as a certified reference material.     

Kinetic spectrophotometric determination of indium/gallium mixtures

A kinetic method is presented for the determination of 0.5–5 μg ml^?1 gallium based on its activating effect on the copper(II)-catalyzed oxidation of 4,4′-dihydroxybenzophenone thiosemicarbazone by hydrogen peroxide. The reaction is monitored spectrophotometrically at 415 nm. Two sets of reaction conditions are established; one for the direct determination of gallium, and another, in which indium affects the gallium response, for determination of indium. Mixtures of these cations can be determined at μg ml^?1 levels and in gallium/indium ratios from 7.5:1 to 1:1.6, with an accuracy and precision of ca. 4.5%.     

Determination of Copper by Atomic Absorption Spectrophotometry After Solid-Liquid Separation by Adsorption of its 1-Nitroso-2-Naphthol Complex onto Microcrystalline Benzophenone

ABSTRACT

A sensitive method for the determination of trace copper by preconcentration and adsorption of its 1-nitroso-2-naphthol complex onto the microcrystalline benzophenone has been developed. Several experimental conditions such as the pH of the solution, the quantities of 1-nitroso-2-naphthol and benzophenone, and the stirring time were optimized for effective separation. Trace copper in a 100 ml water sample was chelated with 2.0 ml of 0.050 M 1-nitroso-2-naphthol at pH 8.0. The solution was heated to 30 °C, stirred vigorously for 10 minutes to adsorb the copper complex quantitatively onto 0.20 g benzophenone. After the microcrystalline benzophenone adsorbed copper complex was filtered and dissolved in acetone, the content of copper was determined by flame atomic absorption spectrophotometry. The interfering effects of concomitant ions were investigated and almost eliminated. The detection limit and the determination limit of this method were 6.9 ngml^?1 and 22.9 ngml^?1, respectively. Recoveries of 103.7 % and 94.2 % were obtained in a tap water and a brass sample, respectively. In the determination of copper in real samples, the values obtained by this proposed method were close to those by GF-AAS.

Based on these experimental results, it is supposed that this method can be applied to the determination of copper in real samples.     

Selective flow-injection determination of residual chlorine at low levels by amperometric detection with two polarized platinum electrodes

Flow-injection amperometry with two polarized platinum electrodes is used for the determination of residual chlorine based on the oxidation of iodide. Interferences of iron(III), copper(II), nitrite and atmospheric oxygen are eliminated in the proposed procedure. The detection limit for residual chlorine is 2 μg l^?1 at a sampling rate of 120 h^?1; linear calibration graphs are obtained up to 0.8 mg 1^?1. A method for the simultaneous flow-injection determination of residual chlorine and copper(II) is also proposed.     

Catalytic test determination of copper on a solid support

A test procedure was developed for the determination of 5 × 10^?7?1 × 10^?3 M copper with the use of the copper-catalyzed reaction of the reduction of molybdophosphoric acid by thiourea on a solid support (paper). The conditions of the indicator reaction and the technique for its conduction were optimized; the pH range in which the acidity of the solution does not affect the time of the reaction was revealed. The calibration plot for the determination of copper was constructed in reaction time-pCu coordinates. The effect of different components on the rate of the indicator reaction was studied. The procedure was approved in the analysis of real and model solutions.     

The Continuous-Addition-of-Reagent Technique in Catalytic Kinetic-Based Determinations

Abstract

A straightforward, inexpensive continuous-addition-of-reagent (CAR) system described elsewhere was applied to kinetic-catalytic analyses. The catalytic effect of copper(l1) on the oxidation of 4,4′-dihydroxybenzophenone thiosemicarbazone (DBPT) by hydrogen peroxide was exploited for this purpose. The reaction was developed by continuously adding DBPT to the reaction vessel containing the other ingredients of the catalytic reaction. The results obtained show the proposed CAR method to surpass its conventional counterpart, and its suitability for the determination of copper in serum samples.     

A Highly Sensitive Method for Determination of Copper (II) in Water Samples for Field Screening

Abstract

A new method has been developed for field screening of copper (II) in water samples, which is based on an enzyme inhibition reaction between copper (II) and nitrate reductase. The concentration of copper (II) was acquired by indirect determination the reaction product (nitrite) with a mini optical reflection sensor. Under the optimum conditions, the calibration graph was linear in the range of 5.0–50 ng mL^?1. The limit of detection was 0.5 ng mL^?1. This method has been used for the field screening of copper (II) with satisfactory results.     

Substoichiometric isotope dilution analysis of copper traces in zinc by adsorptive sampling

The spontaneous deposition of Cu²⁺ from aqueous solutions on a hydrogen-saturated platinum surface as a possibility for the substoichiometric sampling of copper is shown. A sensitive isotope dilution method has been developed for the determination of traces of copper in high purity zinc making use of the spontaneous deposition of microquantities of Cu²⁺ from aqueous solutions of zinc salts on a cathodically polarized platinum surface. If the same platinum surface is used in each run, the saturation values of the deposited copper are practically independent of the concentrations and contents of copper and zinc in the solution. The copper traces were labelled with the product of the⁶⁴Zn(n,p)⁶⁴Cu nuclear reaction. A copper content of 0.18±0.03 ppm in zinc was determined by this method.     

Flow injection determination of trace amounts of copper based on its catalytic effect on the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine by cumene hydroperoxide

A sensitive and selective flow-injection method has been developed for the catalytic determination of copper(II). The method is based on the oxidation of 3,3′,5,5′-tetramethylbenzidine by cumene hydroperoxide as an organic oxidant in an acidic medium. A highly sensitivity has been achieved by adding 2,9-dimethyl-1,10-phenanthroline as an activator and benzyldimethyltetradecylammonium chloride (zephiramine) as a surfactant. The reaction was spectrophotometrically monitored by measuring the increase in absorbance of oxidation product of 3,3′,5,5′-tetramethylbenzidine at 650 nm. The calibration curve was linear over the range of 0.5–3.0 ng mL^?1 at a rate of 30 samples h^?1. Most of the diverse ions did not interfere with the determination of copper up to at least 50-fold excess. The serious interference by iron(III) was eliminated by addition of fluoride. The method was successfully applied to the determination of copper in water samples.     

Extractive-spectrophotometric determination of traces of copper(II) with 4-(p-nitrophenylazo)-2-amino-3-pyridinol

A new extractive-spectrophotometric method for determination of copper(II) with 4-(p-nitrophenylazo)-2-amino-3-pyridinol is proposed. The established stoichiometry and extraction constant are 2:1 ligand:metal and ?1.55, respectively. The molar absorptivity of the complex is 5.19 × 10⁴ liters mol^?1 cm^?1 at 560 nm and Sandell's sensitivity is 1.2 ng cm^?2. The best conditions for determination and effect of other ions are studied. The method proposed is applied in the determination of copper in whisky, liver of fish, and seawater.     

Updated investigation of the reaction between copper and naphthol blue black b and determination of trace amounts of copper in water

The biological dye, naphthol blue black B (NBBB) was found to produce a sensitive reaction with copper(II) at pH over 7. This reaction was very interesting. The complexation of Cu(II) with NBBB happened at pH between 6 and 11 but the redox catalytic reaction happened at pH over 11, where copper(II) served as a catalyst. In this study, ordinary spectrophotometry was limited for use because of the serious interference of excess reactant. A new method, Β-correction principle, was applied because it can eliminate the above interference. This method can give the simple determination of properties of Cu-NBBB complex solution at pH 9.5, which involved the complex ratio, real molar absorptivity, and stability constant (K). Results showed that the formed Cu-NBBB complex occurred as Cu(NBBB) at pH 9.5, its real rather than apparent absorptivity was equal to 7.62 x 10³ L mol^-1 cm^-1 at 630 nm, and its stability constant was 1.32 x 10⁶. The redox catalytic reaction between Cu(II) and NBBB at pH 13 was used to determine trace amounts of copper in water. This reaction was very sensitive and highly selective. Most of the metals did not interfere with the direct determination of copper. The detection limit of copper was 0.002 mg/L, and the recovery was between 90 and 104% with the relative standard deviation of less than 11%. This article was submitted by the author in English.     

Sequential flow-injection spectrophotometric determination of iron(II) and iron(III) by copper(II)-catalyzed reaction with Tiron

A flow injection method for the sequential determination of iron(II) and iron(III) was developed. It is based on the differential reaction kinetics of iron(II) and iron(III) with Tiron in a double-injection FI system. The proposed method employs the accelerating action of copper(II) for the oxidation of iron(II) in the presence of Tiron. A linear calibration graph is obtained for iron (II) and iron(III) in the concentration range 1.8 × 10^–5– 1.8 × 10^–4 mol/L; the throughput of samples is 30 injections/h.     

Ligandless-dispersive liquid-liquid microextraction of trace amount of copper ions

In the present work, a new ligandless-dispersive liquid-liquid microextraction (LL-DLLME) method has been developed for preconcentration trace amounts of copper as a prior step to its determination by flame atomic absorption spectrometry. In the proposed approach 1,2-dicholorobenzene and ethanol were used as extraction and dispersive solvents, respectively. Some factors influencing on the extraction efficiency of copper and its subsequent determination were studied and optimized, such as the extraction and dispersive solvent type and volume, pH of sample solution, extraction time and salting out effect. Under the optimal conditions, the calibration curve was linear in the range of 1.0 ng mL⁻¹-0.6 μg mL⁻¹ of copper with R² = 0.9985. Detection limit was 0.5 ng mL⁻¹ in original solution (3S_b/m) and the relative standard deviation for seven replicate determination of 0.2 μg mL⁻¹ copper was ±1.4%. The proposed method has been applied for determination of copper in standard and water samples with satisfactory results.     

Kinetic method for determination of nanogram amounts of copper(II) by its catalytic effect on hexacynoferrate(III)-citric acid indicator reaction

This paper describes a highly sensitive, selective catalytic-kinetic-spectrophotometric method for the determination of copper(II) concentration as low as 6 ng ml⁻¹. The method is based on the catalytic effect of copper(II) on the oxidation of citric acid by alkaline hexacyanoferrate(III). The reaction was followed by measuring the decrease in absorbance of hexacyanoferrate(III) at 420 nm (λ_max of [Fe(CN)₆]³⁻, ∈ = 1020 dm³ mol⁻¹ cm⁻¹). The dependence of rate of the indicator reaction on the reaction variables has been studied and discussed to propose a suitable mechanism to get a relation between the reaction rate and [Cu²⁺]. A fixed time procedure has been used to obtain a linear calibration curve between the initial rate and lower [Cu²⁺] or log[Cu²⁺] in the range 1 × 10⁻⁷ to 4 × 10⁻⁴ mol l⁻¹ (6.35-25,400 ng ml⁻¹). The detection limit has been calculated to be 4 ng ml⁻¹. The maximum average error is 3.5%. The effect of the presence of various cations, commonly associated with copper(II) and some anions has also been investigated and discussed. The proposed method is sensitive, accurate, rapid and inexpensive compared to other techniques available for determination of copper(II) in such a large range of concentration. The new method has been successfully applied for the determination of copper(II) in various samples.     

Determination of trace amounts of copper(II) by using catalytic redox reaction between methylene blue and ascorbic acid.

A sensitive and selective kinetic-spectrophotometric method is proposed for the determination of microg mL(-1) amounts of Cu2+ based on its catalytic effect on the oxidation of L-ascorbic acid by Methylene Blue in a strongly acidic medium. The reaction is monitored spectrophotometrically by measuring the decrease in color intensity of Methylene Blue at 665 nm. The analysis of Cu2+ ion is performed by a fixed-time method. At a given time of 2 min at pH 2.20 and 32 degrees C, the detection limit is 10 ng mL(-1) and the relative standard deviation for 0.4 microg mL(-1) Cu2+ is 3.60% (n = 6). The method is free from most of the interferences and the effect of diverse ions on the determination of Cu2+ is also reported. The proposed method is virtually specific to copper and has been satisfactorily applied to its determination in electric copper wire samples and pharmaceutical products. Results were also verified by the atomic absorption spectrometry technique (AAS).