Synergetic adsorption of the copper-phenanthroline-tributylphosphate complex at a mercury drop electrode (original) (raw)
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Analytica Chimica Acta, 1993
The voltammetric behaviour of copper in the presence of marine hydrophobic organic matter and soil fulvic acid was examined by differential-pulse anodic stripping voltammetry (DPASV) in sodium perchlorate. These organic substances strongly adsorb on a mercury electrode, thereby affecting the peak current. The extent of this interference is related to the' charge on the electrode during the plating step, but the mechanism of the infhrence on the anodic peak is mainly connected with the stripping step. A cathodic potential step whereby the effects of adsorption can be removed is described. This modified DPASV method was used to evaluate the lability of copper-organic complexes and to elucidate the effects on the anodic current due to the adsorption process.
Synergetic adsorption of copper(II) mixed ligand complexes onto the SEP-PAK C18 column
Analytica Chimica Acta, 1997
The synergetic adsorption onto SEP-PAK Cis column for copper(I1) mixed ligand complexes with the mixture of ligands 2thenoyltrifluoroacetone (TTA), tri-n-butylphosphate (TBP) and 8hydroxyquinoline (oxine)-TBP was investigated as a model of the possible adsorption processes occurring in natural water environments. Measurements were performed in 0.55 M NaCl solution with constant concentrations of ligands and Cu(I1) ions, and constant pH of 6. The remaining concentrations of dissolved Cu(I1) after passing through the column and eluted concentrations of Cu(I1) ions from the column with 0.1 M hydrochloric acid, were determined by the standard addition method at pH=2, using differential pulse anodic stripping voltammetry (DPASV). Synergetic adsorption effects onto the column in the case of the Cu-TTA-TBP mixed ligand complex were observed giving 80% retention of Cu(I1) on the column material. However, no synergetic adsorption was observed with the mixture of oxine-TBP ligands.
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.
Bangladesh Journal of Scientific and Industrial Research, 2011
Complexation and speciation of copper (II) in ppb level with 1,10-phenanthroline (L) in aqueous media have been investigated by differential pulse anodic stripping voltammetry using thin mercury film glassy carbon electrode (TMFGCE). The work was carried out at constant ionic strength of 0.01 mol dm-3 using NaNO3 at ambient temperature. The pH was kept constant at 9.12 ± 0.10 by the addition of borate buffer. Applying the concept of DeFord and Hume, the stability constants of different species of copper with 1,10-phenanthroline were calculated from the variation of peak potential and diffusion current of simple and complexed metal ions under the present experimental conditions. It was found that copper(II) form three complexes (1:1, 1:2 and 1: 3; metal : ligand) with 1,10-phenanthroline. The overall stability constant of copper complexes, MLn can be defined as βMLn= [MLn ]/[M2+][L]n in which M2+ = Cu2+ and L = 1,10-phenanthroline; n is an integer. The values of the stability constan...
Analytical Sciences, 2001
Copper is a metal of prime environmental concern. For the determination of trace elements in aquatic systems, such as rivers, lakes, and sediments, voltammetric techniques are very suitable, owing to their high sensitivity, simplicity and because only a very simple pretreatment of the sample is required. The application of voltammetric techniques in the determination of trace copper has been reviewed. 2 Of these methods, anodic stripping voltammetry on a hanging mercurydrop electrode (HMDE) has gained wide acceptance for copper determination. 3 The disadvantages of this method have also been reviewed. 4 To solve the disadvantages of anodic stripping voltammetry for copper determination, an organic ligand was used to complex with copper(II) with adsorptive property rather than an electrolytic accumulation on the surface of the electrode. A number of studies on the use of AdSV for the determination of copper have been reported 4 and compared. These methods present advantages and disadvantages in relation to the sensitivity, selectivity, and resolution of the adsorptive stripping peak current. Although Ertas et al. 5 used imidazol as a new reagent for the determination of copper by adsorption stripping voltammetry, they did not study the influence of potential interfering ions, and did not use the method for the analysis of synthetic or real samples.
Copper Complexation with Soluble and Surface Freshwaters Ligands
Electroanalysis, 2002
Speciation of copper has been done using samples collected at different times of the year (December 92 and October 93) and in three sites of a polluted river (Este River, Northern Portugal). Filtered samples and the suspended particulate matter were titrated with metal ion and the labile metal concentrations measured by anodic stripping voltammetry (DPASV). An extra peak in the Cu voltammograms has been noticed when titrating filtered samples and its origin was investigated. Results have suggested that the extra peak is due to copper(I) stabilized by ligands adsorbed on the mercury electrode and a model for the electrochemical mechanism is proposed. From titrations of the same samples with zinc, cadmium and lead it has been concluded that there are two types of organics in the river water: macromolecules and small molecules with D ML % D M with higher affinity for soft cations such as Cd(II) and Cu(I), that can be adsorbed on mercury electrode as anions.
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, 1999
A sensitive and selective procedure is presented for the voltammetric determination of copper. The procedure involves an adsorptive accumulation of copper pyrogallol red on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of reduction current of adsorbed complex at À0.2 V (vs. Ag/AgCl). The optimum conditions for the analysis of copper include pH (3.0±4.5), 20 mM pyrogallol red and an accumulation potential of À0.1 V (vs. Ag/AgCl). The peak current is proportional to the concentration of copper over the range 0.4±60 ng ml À1 with a detection limit of 0.07 ng ml À1 with an accumulation time of 60 s. The method was applied to the determination of copper in some analytical grade salts and also in cow's liver tissue.
Analytica Chimica Acta, 1992
Pubhshed data of trace metals m sea water show very large drfferences In strength of organic complexatlon These differences are mcompatlble wtth the expected order of complexatlon by reversible and nonspectitc complexmg hgands Comparison revealed a hnear relatlonshlp between the detection wmdows of the analytIca techmques and the detected metal complexatlon A possible explanation for this relationship 1s that the apparent differences between organic complexatlon of different metals are artifacts when the analytical techmques detect only one or two of many complexmg bgands of greatly varying complexmg ability m the natural water samples Detailed complexahon measurements of copper m samples from the Sargasso Sea and the North Sea were camed out at several detection windows using cathodic strlppmg voltarmnetry and confirmed the presence of several complexmg hgands The detected hgand concentration was found to decrease wth mcreasmg magmtude of the detection wmdow, whereas the conditional stability constant was found to Increase The overall effect was that the degree of metal complexatlon [(ZacuL)-I + 11, where L IS the number of n coeffk~ents, mcreased Hrlth the detection wmdow whereas the complexatlon due to the mdlvldual hgands (cy,,) increased untd a malumum had been reached when the hgand concentration was approximately equal to the metal concentration whereafter it decreased at very high detection windows An additional observation was that the dlssoclatlon rate of organically complexed copper m sea water 1s very slow the process requlrmg more than 1 h to reach eqmhbrmm wrth an added competing hgand The complexation data were used to estimate the total number of hgands and the range of condItiona stability constants The overall complexation of copper m sea water was calculated givmg values for pCu between 13 5 and 1.5 4
Journal of Analytical Chemistry, 2011
No presente trabalho é apresentado um método para a determinação de Cu em amostras de cabelo humano e água por voltametria de redissolução anódica de pulso diferencial. Foi provado que a eletropolimerização do pirrol ocorre em presença do ânion dopante Nitroso-R. O polipirrol dopado com Nitroso-R foi deposido sobre a superfície da platina, e reage com Cu(II) em pHs neutros, originando um complexo. Essa complexação entre o Nitroso-R e o Cu(II) produz o acúmulo de Cu(II) na superfície a partir de a circuito aberto. O eletrodo resultante com Cu(II) complexado foi então transferido para um tampão de acetato, e submetido a voltametria de redissolução anódica, promovendo o aparecimento de um pico de corrente a +0,08 V. Depois da avaliação do comportamento funcional analítico foi construído um gráfico de calibração a partir de 1,2 a 243,9 ng mL-1 e o limite de detecção foi de 0,7 ng mL-1. O método foi utilizado para a determinação de íons cobre em amostras de água e cabelo humano. Os resultados indicam a capacidade do método para a determinação deste íon em amostras reais. Além disso, a rápida e conveniente regeneração do eletrodo permite sua utilização em várias análises. In the present paper a method for the determination of Cu in human hair and water samples by differential pulse anodic stripping voltammetry is presented. It has been proven that pyrrole electropolymerizes in present of Nitroso-R as dopant anion. Nitroso-R doped in polypyrrole film coated on platinum surface then reacts with Cu(II) in neutral pHs giving rise to a complex. This complexation between Nitroso-R and Cu(II) achieves the accumulation of Cu(II) from the sample solutions to the electrode surface at open circuit condition. The resulting electrode with complexed Cu(II) can then transfer to an acetate buffer and subject to anodic stripping voltammetry which promotes the appearance of a peak at +0.08 V. After the evaluation of the analytical performance a calibration graph was constructed from 1.2 to 243.9 ng mL-1 and the detection limit was 0.7 ng mL-1. The method was used for determination of copper ions in water and human hair samples. The results indicate the ability of method for the determination of this ion in real samples. Also, the rapid and convenient regeneration of electrode allows the use of a single modified electrode in multiple analyses.