Sequential injection lab-on-valve simultaneous spectrophotometric determination of trace amounts of copper and iron

A sequential injection (SI) method in a lab-on-valve (LOV) format for simultaneous spectrophotometric determination of copper and iron has been devised. The detection chemistry is based on the complex formation of 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]aniline (5-Br-PSAA) with copper(II) and/or iron(II) at pH 4.6. Copper(II) reacts with 5-Br-PSAA to form the complex which has an absorption maximum at 580 nm but iron(III) does not react. In the presence of a reducing agent only iron(II)-5-Br-PSAA complex is formed and detected at 558 nm. Under the optimum experimental conditions, the determinable ranges are 0.1-2 mg l⁻¹ for copper and 0.1-5 mg l⁻¹ for iron, respectively, with a sampling rate of 18 h⁻¹. The limits of detection are 50 μg l⁻¹ for copper and 25 μg l⁻¹ for iron. The relative standard deviations (n = 15) are 2% for 0.5 mg l⁻¹ copper and 1.8% for 0.5 mg l⁻¹ iron when determined in standard solutions. The recoveries range between 96 and 105% when determining 0.25-2 mg l⁻¹ of copper and 0.2-5 mg l⁻¹ of iron in artificial mixtures at copper/iron ratios of 1:10 to 5:1. The proposed SI-LOV method is successfully applied to the simultaneous determination of copper and iron in multi-element standard solution and in industrial wastewater samples.     

Spectrophotometric determination of copper as a dithiocarbamate by flow injection analysis

Copper(II) ions (1–20 mg l^?1) are determined at 385 nm by injection into an aqueous carrier solution containing EDTA (0.05 M), carbon disulphide (0.03%) and diethanolamine (0.1%) in aqueous ammonia solution (0.5%) adjusted to pH 8.0. Chromium(VI) and, to a minor extent, iron(III) interfere. In the absence of EDTA, cobalt, iron(II), nickel, and manganese ions interfere but the sensitivity to copper is higher.     

Spectrophotometric Determination of Copper(II) as the Azide Complexes,in the Presence of Iron(III) Cations

Abstract

A method for the spectrophotometrio determination of copper(II), in the presence of iron(III) cations (excess), was stablished. The masking of iron is made with sodium fluoride salt in 50 % (v/v) water/acetone medium. In the recommended conditions, absorbances for cupric complexes are measured at 435 nm where molar absorptivity is 6.00 × 10³ 1 mol^?1 cm^?1.

The stable ayetern obeys Beer's law and is suitable for the copper determination in concentration range from 2.0 to 9.0 mg 1^?l. The iron(III) ion interference (until ca. 600 mg 1^?l) can be completely suppressed. The influence of diverse ions and several others factore were studied.

The results show that copper(II) can be accurately determined by azide apectrophotometric method, if the samples were suitablely treated by the recommended procedure.     

Synthesis of o,o′-dihydroxyazo compounds and their application to the determination of magnesium and calcium by flow injection analysis

Seven _o,o′-dihydroxyazo dyes were synthesized and examined as spectrophotometric reagents for magnesium and calcium. These reagents are highly sensitive for magnesium (? = 47 000) and calcium (? = 39 000 l mol^?1 cm^?1). Of the reagents synthesized, 2-(2-hydroxy-3,6-disulfo-1-naphthylazo)-5-(N,N-diethylamino)phenol was the best because of its ease of preparation and purification, and its stability in alkaline solution. This dye was applied in the determination of magnesium and calcium by flow injection analysis. The total concentration of magnesium (0.1–1.2 mg 1^?1) and calcium (0.4–4.0 mg 1^?1) was determined by masking iron(III), aluminium(III), copper(II), zinc(II), manganese(II) and cadmium(II) with 2,3-dimercapto-1-propanol (DMP) and triethanolamine (TEA). Magnesium was determined by masking calcium and the other metal ions with a ligand buffer containing barium(II)—EGTA, DMP and TEA. The amount of calcium was obtained as the difference between the two peak heights. Results for the determination of magnesium and calcium in potable water and serum are presented.     

The masking effect of iron(III) on the interference from nickel and copper in the determination of tellurium by hydride generation/atomic absorption spectrometry

Iron(III) can minimize the serious interferences from copper(II) and nickel(Il) on the determination of tellurium by hydride generation/atomic absorption spectrometry. The optimal concentrations were found to be 1 g l^?1 and 2 g l^?1 Fe (III) in 4.0 mol l^?1 HCl in presence of nickel (II) and copper (II), respectively. The signals were only 25 % lower in a solution of 1.6 g 1^?1 Ni(II) than for a nickel-free solution. For copper (II), reasonable sensitivity was retained in the presence of 100 mg l^?1 Cu(II).     

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.     

Synthesis of bidentate pyridylazo and thiazolylazo reagents and the spectrophotometric determination of copper in a flow-injection system

Some pyridylazo and thiazolylazo compounds were synthesized as spectrophotometric reagents for copper(II). The water-soluble bidentate ligand, 4-(3,5-dibromo-2-pyridylazo)-N-ethyl-N-(3-sulfopropyl)aniline (3,5-diBr-PAESA), provides the greates sensitivity, forming a 1:2 Cu:L in the presence of sodium dodecylsulfate. The molar absorptivity of the complex is 1.24 × 10⁵ l modl^?1 cm^?1 at 638 nm. Copper(II) (10–200 μg l^?1) is easily and quickly (60 h^?1) determined in a flow-injection system. Application to the determination of copper(II) in serum is described.     

Flow-injection analysis for power plants: Evaluation of detectors for the determination of control parameters in conditioned water—steam cycles

Flow-injection methods are described for monitoring water in power-plant cycles. The parameters considered are pH (in the range 5.5–9.5), using a flat-headed combined electrode, ammonia (0.2–3 mg N l^?1), using Nessler, Berthelot and gas-diffusion methods, hydrazine (0.025–0.3 mg l^?1), using the dimethylamino-4-benzaldehyde method, copper (0.02–0.2 mg l^?1), using bathocuproin and methods based on ion-selective electrodes, iron (0.01–10 mg l^?1), using phenanthroline, ferrozine and biamperometric methods, and silicon (0.02–0.1 mg l^?1), using the heteropoly blue complex, with two different types of reducing agent [tin(II) chloride and ascorbic acid]. The parameters considered were precision, analysis frequency and application range. The results obtained showed that flow-injection methods perform well in terms of sensitivity and analysis frequency and suggested the possibility of transferring this methodology to analytical systems in power plants.     

Flow-injection spectrophotometric determination of glucose in blood plasma with bindschedler's green leuco base as color reagent

The hydrogen peroxide produces in the oxidation of glucos in an immobilized glucose oxidase reactor is determined by using Bindschedler's green (leuco base) as color reagent with iron(II) as catalyst; the increase in the absorbance at 725 nm is measured. For 100-μl samples, calibration was almost linear in the range 0–2.5 mg l^?1 glucose; the relative standard deviation for 1 mg l^?1 glucose was 0.6% (n=10) and the detection limit (S/N= 2) was 0.02 mg l^?1. The injection rate was 20 h^?1. Glucose was determined satisfactorily in control sera and in real blood sera.     

Application of the iron(III)/3,4-dihydroxybenzaldehyde 4-nitrophenylhydrazone complex for the analysis of sulphide/fluoride/phosphate mixtures by spectrophotometry or atomic absorption spectrometry

3,4-Dihydroxybenzaldehyde 4-nitrophenylhydrazone reacts with iron(III) to form a red complex extractable into methyl isobutyl ketone. Sulphide, fluoride and phosphate inhibit the formation of the complex. Sulphide and fluoride are masked with Cu(II) and Al(III), respectively. These properties are used to determine sulphide (0.15–4 mg l^?1), fluoride (0.3–9 mg l^?1) and phosphate (0.3–8 mg l^?1) in mixtures by spectrophotometry or atomic absorption spectrometry.     

Iron(III) as releasing agent for copper interference in the determination of selenium by hydride-generation atomic absorption spectrometry

Iron(III0 has a very effective releasing effect on the depressive interference from copper(II) on the determination of selenium by hydride-generation atomic absorption spectrometry. In solutionwith 100 mg 1^?1 Cu(II), 10 μg 1^?1 Se(IV) and 2.0 mol l^?1 HCl, the absorbance obtained was much higher when 8 g 1^?1 Fe(III) was added than for any earlier releasing agent.     

Flow-injection spectrophotometric determination of fluoride by using the zirconium/alizarin red S complex

A spectrophotometric flow-injection procedure is described for fluoride in aqueous samples. The method is based on the decrease in absorbance of the zirconium/alizarin red S complex at 520 nm; linear response is obtained for the range 0.1–10 mg l^?1 fluoride at a sampling rate of 100 h^?1. Aluminum(III), iron(III) and phosphate interfere.     

Alkanohydroxamic acids in the accurate computer-aided spectrophotometric determination of copper(II)

The computer-aided spectrophotometric determination of copper(II) (0.03–1 mg l^?1) with 2-amino-N,3-dihydroxypropanamide or 2-amino-N,3-dihydroxybutanamide as reagent is reported. In the LESSDAD program used, a least-squares is applied for simultaneously calculating the analytical concentrations in solutions of several substances; the data needed are the pH of the solution, experimental absorbances, known molar absorptivities and the relevant equilibrium constants. The method is rapid and the results obtained were accurate and precise.     

Flow-injection spectrophotometric determination of palladium in catalysts and dental alloys with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropyl-amino)aniline

2-(5-Bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)aniline rapidly forms a water-soluble complex with palladium in an acetate-buffered medium at pH 3.2.The molar absorptivity of the complex is 9.84×10⁴l mol^?1 at 612 nm. The calibration graph is linear over the range of 10–100 μg l^?1 palladium; the detection limit is 2 μg l^?1 and the relative standard deviation is 0.6% for 100 μg l^?1 palladium. The sample throughput is 50 h^?1. Divalent transition metals (Fe, Ni, Co) do not interfere at levels from 2 to 10 mg l^?1. Interference from copper is prevented by adding 10^?3 M EDTA solution to the carrier stream. Palladium in solutions of catalysts and dental alloys can be determined selectively, sensitively and rapidly.     

Catalytic activities of polymer‐supported metal complexes in oxidation of phenol and epoxidation of cyclohexene

The metal complexes of N, N′‐bis (o‐hydroxy acetophenone) propylene diamine (HPPn) Schiff base were supported on cross‐linked polystyrene beads. The complexation of iron(III), copper(II), and zinc(II) ions on polymer‐anchored HPPn Schiff base was 83.4, 85.7, and 84.5 wt%, respectively, whereas the complexation of these metal ions on unsupported HPPn Schiff base was 82.3, 84.5, and 83.9 wt%. The iron(III) complexes of HPPn Schiff base were octahedral in geometry, whereas copper(II) and zinc(II) ions complexes were square planar and tetrahedral. Complexation of metal ions increased the thermal stability of HPPn Schiff base. Catalytic activity of metal complexes was tested by studying the oxidation of phenol and epoxidation of cyclohexene in the presence of hydrogen peroxide. The polymer‐supported HPPn Schiff base complexes of iron(III) ions showed 73.0 wt% conversion of phenol and 90.6 wt% conversion of cyclohexene at a molar ratio of 1:1:1 of substrate to catalyst and hydrogen peroxide, but unsupported complexes of iron(III) ions showed 63.8 wt% conversion for phenol and 83.2 wt% conversion for cyclohexene. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 93.1 and 98.3 wt%, respectively with supported HPPn Schiff base complexes of iron(III) ions but was lower with HPPn Schiff base complexes of copper(II) and zinc(II) ions. Activation energy for the epoxidation of cyclohexene and phenol conversion with unsupported HPPn Schiff base complexes of iron(III) ions was 16.6 kJ mol^?1 and 21.2 kJ mol^?1, respectively, but was lower with supported complexes of iron(III) ions. Copyright © 2007 John Wiley & Sons, Ltd.     

Flow-Injection Determination of Iron Based on Its Catalysis on the Oxidation Reaction of Xylenol Orange by Potassium Bromate

A flow injection system is proposed for catalytic kinetic spectrophotometric determination of trace iron(II + III). The involved reaction is based on the catalytic effect of iron(III) on oxidation reaction of xylenol orange by potassium bromate to form a blue-violet complex. Iron(II) is also determined, being oxidized to iron(III) by potassium bromate. The calibration graph is linear in the range of 0.02–10.0 µg l^?1 and 10.0–1100 µg l^?1. The relative standard deviation is 1.5% for 4.0 µg l^?1 iron(III) and 2.3% for 60.0µg l^?1 iron(III) (n = 11). The presented system was applied successfully to the determination of iron in natural waters.     

Determination of cobalt(II), copper(II) and iron(II) by ion chromatography with chemiluminescence detection

An optimized flow-injection manifold for the chemiluminescence determination of cobalt(II), copper(II), iron(II) and chromium(III) by their catalytic effect on the luminol reaction is described. Detection limits are 0.0006, 0.08, 0.3 and 0.1 ng ml^?1, respectively. The suppression effect of several carboxylic acids on the emission intensity is discussed. A procedure for the separation of cobalt(II), copper(II) and iron(II) on a low-capacity, silica-based cation-exchange column, using 5 mM oxalic acid at pH 4.2 as the mobile phase and post-column detection via the luminol reaction, is also described. Detection limits for cobalt(II) and copper(II) are 0.01 and 5 ng ml^?1, respectively.     

Luminescent hexanuclear Cu(I)-cluster for the selective determination of copper

For the first time, the formation of a luminescent hexanuclear cluster has been used for the selective determination of copper. In aqueous solutions, the non-luminescent ligand N-ethyl-N′-methylsulfonylthiourea (EMT) forms an intensely red luminescent hexanuclear Cu(I)-cluster with an emission maximum at 663 nm only with Cu(II) ions. The intensity of the luminescence is proportional to the Cu(II) concentration and allows for selective Cu determinations in the μg l⁻¹-range. Ubiquitous metal ions such as Fe(III), Al(III), Ca(II), Mg(II), and alkaline metal ions, as well as other heavy metal ions, e.g. Co(II), Ni(II), Zn(II), Cd(II), Hg(II), and Pb(II) are tolerated in concentrations up to 50 mg l⁻¹. The detection limit for Cu(II) in aqueous solution, calculated according to Funk et al. [Qualitätssicherung in der Analytischen Chemie, Verlag Chemie, Weinheim, 1992], is 113 μg l⁻¹. The cluster formation has been used for the quantitative analysis of copper in tap water and in industrial water, as well as for the localization of copper adsorbed by activated-sludge flocs.     

Spectrophotometric determination of copper(II) in natural waters, vitamins and certified steel scrap samples using acetophenone-p-chlorophenylthiosemicarbazone

A very simple, highly sensitive and selective spectrophotometric procedure was developed for the determination of copper(II). It is based on the reaction at pH 4–9 between the synthesized acetophenone-p-chlorophenylthiosemicarbazone (A-p-ClPT) and Cu(II) forming a green complex, Cu(II):A-p-ClPT (1:2), that floats quantitatively with oleic acid (HOL) surfactant. It exhibits a constant and maximum absorbance at 600 nm in both aqueous and surfactant layers. Beer’s law is obeyed over the concentration range 0.25–6.35 mg l^?1 with a detection limit of 0.021 mg l^?1 for a standard aqueous solution of Cu(II) with a concentration of 3.82 mg l^?1 (calculated on the basis of 3σ) and molar absorptivities of 5.5 × 10³ and 1.3 × 10⁴ mol l^?1 cm^?1 in aqueous and surfactant layers, respectively. Sandell’s sensitivity was calculated to be 0.244 μg cm^?2 and the relative standard deviation (n = 9) was 0.19%. The different analytical parameters affecting the flotation and determination processes were examined. The proposed procedure has been successfully applied to the analysis of Cu(II) in natural waters, certified scrap steel samples and vitamin samples. The results obtained agree well with those samples analyzed by atomic absorption spectrometry (AAS). Moreover, the flotation mechanism is suggested based on some physical and chemical studies on the solid complexes isolated from aqueous and surfactant layers.     

The Application of strongly oxidizing agents in flow injection analysis : Part 1. Silver(II)

The application of silver(II) as a powerful oxidizing reagent in flow injection analysis is described in detail. Under the experimental conditions, the half-life of the very unstable silver(II) was about 120 s. Nevertheless, various organic and inorganic substances could be determined. Spectrophotometric detection was at 390 nm where silver(II) in nitric acid solutions absorbs strongly. As neither iron(III) nor copper(II) reacts with silver(II), oxidizable compounds can be determined in the presence of large amounts of these species. Special attention is given to manganese(II), which can be determined selectivity by this method in the range 10^?5–10^?4 mol l^?1.