Electrochemical Studies on Complexation and Speciation of Copper(II) in ppb Level with 1,10-Phenanthroline in Aqueous Media (original) (raw)
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Cathodic stripping voltammetry of the copper-1,10-phenanthroline complex
Electroanalysis, 1995
Cathodic stripping voltammetry of copper, based on the accumulation and reduction of its complex with 1,lO-phenanthroline (phen), has been studied. The complex is reduced in two steps from Cul-phen and Cu"-phen to copper amalgam at potentials of-0.43 and-0.62V vs. Ag/AgCl, respectively. The reduction processes are strongly dependent on the pH of the solution, as well as on the concentration of the metal ion and ligand. The reduction mechanism of both complexes was established. The detcction limit for copper in 0.55mol/LNaC1 with 20min accumulation at 0.OV vs. Ag/AgCI, measuring the reduction peak of the Cut-phen complex at-0.43 V vs. Ag/AgCI by SWV, was found to be about 5 x 10-lomol/L. The reaction parameters were calculated by square-wave voltammetry (SWV), i.e., transfer coefficients aCu~.phen = 0.31 and N~~I I .~~~~ = 0.45, and the maximum surface concentrations rCu~.phen = (2.02 f 0.08) x lo-" mol/cm2 and ~,-"II phen = (2.83 i 0.12) x lo-'* rnol/cm2. Measurements of the copper content in natural seawater samples were performed as well.
Cyclic voltammetric studies of some bis (phenanthrolines )copper (II) complexes
2007
The electrochemical properties of some bis(phenanthrolines)copper(II) complexes, [Cu(NN) 2 ](ClO 4 ) 2 (NN denotes 1,10-phenanthroline (phen); 4,7-diphenyl-1,10-phenanthroline (bathophen); 2,9-dimethyl-1,10-phenanthroline (dmp) and 2,9-diphenyl-1,10-phenanthroline (dpp) have been studied by cyclic voltammetry at a platinum working electrode in dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF) containing 0.1 M tetrabutyl ammonium perchlorate (TBAP) as the supporting electrolyte. All these complexes display a quasireversible Cu 2+/+ redox couple. Both the electron-donating methyl groups and electron-withdrawing phenyl groups at the 2,9-positions of the phen ligand elevate the Cu 2+/+ redox potentials of the [Cu(dmp) 2 ](ClO 4 ) 2 and [Cu(dpp) 2 ](ClO 4 ) 2 complexes. The redox potentials of [Cu(dmp) 2 ] 2+ are nearly 50 mV more positive than that of [Cu(dpp) 2 )] 2+ in a given solvent. It is found that the Cu 2+/+ reduction potential (E pc ) as well as formal potential (E 0' ...
Sensors, 2008
Using a paraffin impregnated graphite electrode (PIGE) and mercury-modified pyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNA purine base solutions have been studied by cyclic (CV) and linear sweep voltammetry (LSV) in connection with elimination voltammetry with linear scan (EVLS). In chloride and bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with two cathodic and two anodic potentially separated signals. According to the elimination function E4, the first cathodic peak corresponds to the reduction Cu(II) + e -→ Cu(I) with the possibility of fast disproportionation 2Cu(I) → Cu(II)+ Cu(0). The E4 of the second cathodic peak signalized an electrode process controlled by a surface reaction. The electrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by one cathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodic stripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where the reduction of copper ions took place and Cu(I)-purine complexes were formed. By using ASV and CSV in combination with EVLS, the sensitivity of Cu(I)-purine complex detection was enhanced relative to either ASV or CSV alone, resulting in higher peak currents of more than one order of magnitude. The statistical treatment of CE data was used to determine the reproducibility of measurements. Our results show that EVLS in connection with the stripping procedure is useful for both qualitative and quantitative microanalysis of purine derivatives and can also reveal details of studied electrode processes. Sensors 2008, 8 430
Analytica Chimica Acta, 1994
In the framework of electrochemical investigations on the synergetic adsorption of mixed ligand complexes at the mercury drop electrode, a cathodic stripping voltammetric method for the determination of copper(I1) as mixed ligand complex with IJO-phenanthroline (Phen) and tributylphosphate (TBP) in aqueous solutions was examined. The measurements were based on the accumulation of the copper-phenanthroline complex on the mercury drop surface covered with a layer of TBP molecules. The copper reduction response is strongly enhanced due to the formation of a mixed complex which is very hydrophobic and, therefore, strongly adsorbs at the electrode surface. The effect of various parameters (pH, metal and ligand concentrations, time and potential of accumulation) on the reduction process is examined. The voltammetric procedure was then applied to the detection of copper in natural water samples.
Marine Chemistry, 1984
Van den Berg, C.M.G., 1984. Determination of the complexing capacity and conditional stability constants of complexes of copper(II) with natural organic ligands in seawater by cathodic stripping voltammetry of copper-catechol complex ions. Mar. Chem., 15: 1-18. A new method is proposed for the determination of complexing capacities and conditional stability constants for complexes of copper(II) with dissolved organic ligands in seawater. This method is based on ligand competition by the added ligand catechol for free metal ions. The concentration of copper-catechol complex ions is measured with great sensitivity by cathodic stripping voltammetry. The concentration of the free copper ion is calculated from the concentration of copper-catechol complex ions. Ligand concentrations and conditional stability constants are obtained from a titration of the ligands with copper. Two techniques for treatment of the data are compared. A seawater sample, originating from open oceanic conditions, is analysed and two complexing ligands were detected, having concentrations of 1.1 x 10-8 and 3.3 x 10-8M, and conditional stability constants (log K~uL) of 12.2 and 10.2, respectively.
2012
The cyclic voltammetric behaviour of copper (II) -Ethylenediamine systems with [Cu(II)]: [en] = 1:10, 1:100, 1:500 and 1:600 molar ratios, 1mM CuSO 4 .5H 2 O in Aqueous 0.2M NaClO 4 have been studied at pH values 7.10, 9.10 and 10.85 using cyclic voltammetry. The electrode process show quasi reversible one electron charge transfer preceded and followed by chemical reaction at glassy carbon electrode (G C E). At pH 10.85, the CV features for 1:10 and 1:100 molar ratios differ significantly as regards the oxidation process, while that of 1:100 and 1:500 are generally identical. Ipc 1 and Ipa 1 for 1:6x10 -3 M are significantly small indicating the formation of binuclear copper (II) complex or formation of Cu(en) 3 2+ in solution. At a given ligand ratio and at a given pH, Epc 1 , shifts anodically in the order 1:600 1:500≈1:100≈1:10.
Square-wave voltammetry of copper?phenanthroline?tributylphosphate complex
The Analyst, 1994
The mechanism of synergetic adsorptive accumulation of copper(n)-phenanthroline-tributylphosphate (Cu-phen-TBP) complex at the mercury drop electrode surface has been described. The behaviour and characteristics of the CU" mixed ligand complex was studied and the relationship between the properties of square-wave response and the parameters of a charge transfer and of the excitation signal are discussed. Square-wave voltammetric response of the Cu-phen-TBP complex are analysed according to the theoretical results.
Analytica Chimica Acta, 2010
Different procedures of voltammetric peak intensities determination, as well as various experimental setups were systematically tested on simulated and real experimental data in order to identify critical points in the determination of copper complexation parameters (ligand concentration and conditional stability constant) by anodic stripping voltammetry (ASV). Varieties of titration data sets (Cu measured vs. Cu total) were fitted by models encompassing discrete sites distribution of one-class and two-class of binding ligands (by PROSECE software). Examination of different procedures for peak intensities determination applied on voltammograms with known preset values revealed that tangent fit (TF) routine should be avoided, as for both simulated and experimental titration data it produced an additional class of strong ligand (actually not present). Peak intensities determination by fitting of the whole voltammogram was found to be the most appropriate, as it provided most reliable complexation parameters. Tests performed on real seawater samples under different experimental conditions revealed that in addition to importance of proper peak intensities determination, an accumulation time (control of the sensitivity) and an equilibration time needed for complete complexation of added copper during titration (control of complexation kinetics) are the keypoints to obtain reliable results free of artefacts. The consequence of overestimation and underestimation of complexing parameters is supported and illustrated by the example of free copper concentrations (the most bioavailable/toxic specie) calculated for all studied cases. Errors up to 80% of underestimation of free copper concentration and almost two orders of magnitude overestimation of conditional stability constant were registered for the simulated case with two ligands.
European Journal of Inorganic Chemistry, 2014
Two series of copper(I) complexes with diethoxyphosphorylsubstituted 1,10-phenanthroline ligands were synthesized and characterized in the solid state and in solution. The first comprised mixed-ligand Cu I complexes with phenanthroline and triphenylphosphine. The second series includes bis-chelates with two phenanthroline ligands. According to the Xray data for the six complexes, the ditopic phenanthroline ligands exhibit bidentate coordination to the copper(I) atom through two nitrogen atoms in both series. Solution equilibria involving different phenanthroline copper(I) species were studied by 1 H and 31 P NMR spectroscopy, electrochemistry, and spectroelectrochemistry. The solution speciation of these labile complexes is different for these two series and depends on the nature of solvent and the location of the phosphorus [a] www.eurjic.org FULL PAPER Scheme 1. Structures of diethoxyphosphoryl-substituted 1,10-phenanthrolines 1a-1f.
Stability of ternary copper and nickel complexes with 1,10-phenanthroline
Journal of Inorganic Biochemistry, 1992
This work presents a comparative analysis of the behavior of copper and nickel (II) towards the formation of mixed-ligand complexes with l,lO-phenanthroline as primary ligand. Secondary ligands were acetylacetonate, salicylaldehydate (O-O donors), glycinate, or tyrosinate (O-N donors). The formation of hexacoordinate complexes was observed in the case of nickel.