Cupric Ion-selective Electrode Research Articles

Development of a Technology for Online Measurement of Total and Water-Soluble Copper (Cu) in PM2.5

A novel monitor for online, in situ measurement of copper (Cu) in ambient fine and ultrafine particulate matter (PM) was developed based on a recent published high flow rate aerosol-into-liquid collector. This aerosol-into-liquid collector operates at 200 L/min flow and collects particles directly as highly concentrated slurry samples. The Cu concentration in slurry samples is subsequently determined by a cupric ion selective electrode (ISE). Laboratory tests were conducted to evaluate the performance of the cupric ISE. The calibration curve of the cupric ISE was determined using Cu(NO3)2 standard solutions prepared by serial dilution. As part of the evaluation, the effects of ionic strength, temperature and pH of the aerosol slurry sample on the cupric ISE measurement were also evaluated. The Cu measurement system performance was evaluated by collecting and measuring samples of lab-generated Cu(NO3)2 aerosols with known mass concentration. Overall, very good agreement between the theoretical and measured...

Long-Term Interaction of Copper with a Deoxygenated Neutral Aqueous Solution

The evolution of the open-circuit potential, cupric ion concentration and electrochemical impedance during immersion of Cu OFP in deoxygenated borate buffer solution (pH 7.3) in a closed cell featuring a Pd membrane was monitored at 25°C for up to 3000 h (ca. 4 months). It was demonstrated that the steady-state rest potential of a copper electrode is very close to that of a cupric ion selective electrode for most part of the duration of the respective experimental runs and therefore can be considered to be determined by traces of divalent copper in the aqueous solution. No evidence of sustained corrosion of copper was found by the methods employed. The results were interpreted by a kinetic model previously proposed for shorter exposures with the addition of the disproportionation reaction of monovalent copper to explain the persistence of soluble divalent copper at longer exposure times. A hypothesis on possible hydrogen formation by a catalytic mechanism involving adsorbed CuOH is advanced and a preliminary estimate of the upper limit of hydrogen production rate is obtained using calculation results from the kinetic model.

A mechanism of interaction of copper with a deoxygenated neutral aqueous solution

The electrochemical behaviour of Cu exposed to deoxygenated borate buffer for 330 h was characterised by chronopotentiometry, voltammetry, electrochemical impedance spectroscopy and cupric ion-selective electrode measurements. The results were interpreted by a quantitative kinetic model of the copper/electrolyte interface featuring two adsorbed intermediates produced by interaction of Cu with adsorbed water and electrochemical reduction of soluble divalent copper. The model reproduces successfully both the current vs. potential curve and the electrochemical impedance spectra around the open-circuit potential. On the basis of the experimental and calculation results, tentative conclusions for the interplay between hydrogen generation and copper corrosion are drawn.

Measurement of Free Copper(II) ions in Water Samples with Polyvinyl alcohol as a Binding Phase in Diffusive gradients in Thin-films

A technique for the selective measurement of diffusive gradients in thin-films (DGT) for free Cu2+ ions was developed using a 0.030 M solution of polyvinyl alcohol (PVA) as the liquid binding phase with the liquid-type DGT devices (PVA DGT). The PVA DGT had a substantial binding capacity at pH 5.6 - 8.6 and concentrations of competitive Na+ up to 0.7 M. The measurements of PVA DGT and cupric ion selective electrode (Cu-ISE) for free Cu2+ in synthetic river water (recovery = 97.51 +/- 2.58% for PVA DGT and recovery = 98.25 +/- 1.46% for Cu-ISE), in spiked river water (recovery = 24.99 +/- 3.55% for PVA DGT and recovery = 26.32 +/- 3.33% for Cu-ISE) and in spiked industrial wastewater (recovery = 4.21 +/- 3.13% for PVA DGT and recovery = 5.10 +/- 2.78% for Cu-ISE) were equivalent. The results showed that PVA DGT could measure selectively the free Cu2+ ion concentrations in water samples.

Determination of activity coefficients and relative partial molar free energies for copper sulfide mineral bioleaching solutions by ion-selective electrode

This work reports the results about the determination of mean activity coefficients and relative partial molar free energies for copper sulfide mineral bioleaching solutions by potentiometric method at 25 °C. The experimental potentiometric data were obtained by combining a diamond film—cupric ion-selective electrode (Cu(II) ISE), containing a KNO 3 filling solution, and an Ag/AgCl electrode. The measurements were performed, at constant ionic strength, in different series of copper sulfide mineral bioleaching solutions. The non-ideal behavior of the system was described on the base of the Pitzer ion-interaction model for mixed salts. Meanwhile, the relative partial molar free energies of bioleaching solution were obtained. The determination of the thermodynamic properties offers a basic data for the study of copper sulfide mineral bioleaching solutions.

Free cupric ions in contaminated agricultural soils around a copper mine in eastern Nanjing City, China

To determine the environmental free metal ion activity was a recent hot issue. A method to measure low-level free cupric ion activity in soil solution extracted with 0.01 mol/L KNO 3 was developed by using cupric ion-selective electrode (ISE) and calibrating with Cu-buffer solution. Three copper buffers including iminodiacetic acid (IDA), ethylenediamine (EN), and glycine (Gly) were compared for calibrating the Cu-ISE curves in the range of free cupric ions (pCu 2+) 7–13. The Cu-EN buffer showed the best electrode response and thus was applied as the calibration buffer. The pCu 2+ of 39 contaminated agricultural soils around a copper mine was measured, ranging from 5.03 to 9.20. Most Cu in the soil solutions was found to be complexed with dissolved soil organic matters, averaging 98.1%. The proportion of free Cu 2+ ions in the soil solutions decreased with the increasing of solution pH. Soluble Cu and free Cu 2+ ions concentrations were analyzed by multiple linear regressions to evaluate the effects of soil properties on metal levels and speciation. The results showed that soil solution pH was the most significant factor influencing pCu 2+ (with R 2 value of 0.76), while not important for the soluble Cu concentration.

Evaluation of Cu–Ethylenediamine Metal Ion Buffers as Calibrants for Ion‐Selective Electrode Measurement of Copper in Fresh Water Systems

AbstractAn investigation was made into the accuracy of cupric ion selective electrode (ISE) measurement of Cu in solutions approximating acidic freshwaters with Cu‐ethylenediamine buffers used as the calibrants. This method overestimates the free Cu compared with calibration using Cu(NO3)2 standards, the standard addition method, and speciation modelling calculations. Statistical tests showed a small, but significant, difference between the intercepts of the linear Nernstian regressions of the calibration plots of Cu‐en buffer standardisation and direct calibration with Cu(NO3)2 standards in matrix that matches the samples. The difference in the intercepts, which corresponds with Eo values of the electrode, is not well understood, but is possibly caused by potentially interfering cations such as Fe2+. The results of this study showed that down to 10−8 M Cu2+, where a linear Nernstian response is possible, the Cu ISE is probably better calibrated using Cu standards prepared in the same matrix as the sample solutions to avoid potential matrix effects.

Comparison of [Cu2+] Measurements in Lake Water Determined by Ligand Exchange and Cathodic Stripping Voltammetry and by Ion-Selective Electrode

While there has been a proliferation of techniques for measuring free metal ion concentrations and complexation in natural waters, there has been little direct intercomparison among methods. Here we report the results of an intercomparison among different methods used to determine free cupric ion concentration ([Cu2+]) and organic complexation in lake water samples. The techniques used were potentiometric measurement with a cupric ion-selective electrode (Cu-ISE) and ligand exchange methods involving the addition of three well-characterized ligands with dif ferent binding affinities for copper (catechol, 8-hydroxyquinoline, and tropolone) followed by measurement of the Cu chelates of these ligands by adsorptive differential pulse cathodic stripping voltammetry (DPCSV). Good agreement was found among relationships between [Cu2+] and the total concentration of natural copper species ([Cunat]) determined via titration with the three ligand exchange/DPCSV methods. Relationships between [Cu2+] and [Cunat] measured by these methods also agreed with those determined with a cupric ion electrode within the overlapping range of detection windows for each method ([Cunat] = 40−100 nM). At lower Cu concentrations, the Cu electrode gave er roneously high [Cu2+] readings, apparently due to a failure of the electrode membrane to equilibrate with the sample. The agreement among the different methods provides support for the validity of each individual method of measuring [Cu2+] and natural Cu complexation. By combining Cu titration data measured by DPCSV and Cu-ISE, we obtained a more complete description of the Cu-complexing characteristics of water samples from two Swiss lakes than could be obtained with any single method. Equilibrium modeling of this composite data indicated the presence of at least three ligand classes. These ranged in concentration from 38 ± 19 nM for the strongest binding ligand class, which had conditional binding constants in the range of 1015 at pH 7.8−8.0, to 8 ± 2 μM for the weakest class of ligands, which had a conditional constant of 108.6 M-1.

The effects of water chemistry on the toxicity of copper to fathead minnows

AbstractThe effects of various water chemistry parameters on the toxicity of copper to larval fathead minnows were investigated. Increased pH, hardness, sodium, dissolved organic matter, and suspended solids each caused toxicity to decrease on the basis of total copper concentrations. In contrast, added potassium resulted in increased toxicity. Alkalinity had no observed effect on total copper LC50s, but its effects might have been masked by those of the cations added with it. In most cases, the effects of water chemistry were found to be similar for different endpoints (growth, survival at different durations), but there were differences in the relative magnitude of some effects across these endpoints. Over all experimental treatments, 96‐h total copper LC50s varied 60‐fold. Every water chemistry parameter also caused toxicity to vary significantly when expressed on the basis of cupric ion selective electrode measurements, sometimes more so than on the basis of total copper. Therefore, this study does not support attributing to cupric ion a singular importance in regulating toxicity to this test organism. A variety of copper species might be contributing to toxicity and it is evident that toxicity is also affected by water chemistry in ways not related to copper speciation.

Ion-selective electrode measurements of copper(II) activity in contaminated soils

A method is presented for the use of a cupric ionselective electrode to determine the free copper activity in 0.01 M CaCl2 soil solution extracts. Ionic strength variations and the presence of aluminum caused no significant interferences. The method was applied to 18 soils with wide-ranging copper levels. The pCu2+ varied between 6.33 and 12.20. Acidic soils have a very high cupric ion activity even though they are not considered to be contaminated with copper. Soils considered contaminated with respect to total copper also have free pCu2+ activities below 10, which is close to the toxicity threshold determined in aquatic ecotoxicological studies. All mineral soils have free copper activities close to or below the values expected from pH-dependent soil equilibration studies.

Destructive Effect of Aspartame on Ascorbic Acid in Cu‐catalyzed Solutions

ABSTRACTThe effect of aspartame on the early stage of ascorbic acid oxidation in solutions was studied by measuring ascorbic acid retention in an open system at 30°C and the oxygen uptake in a closed system at 33°C. Comparisons were also made between aspartame (0.06% and 0.12%) and sucrose (10% and 20%) in Cu‐catalyzed and noncatalyzed solutions at 30°C. Copper activity in aspartame solution was measured by using a cupric ion selective electrode. Aspartame increased the rate of ascorbic acid oxidation in all tested solutions. In the presence of copper the oxidation rate of ascorbic acid was significantly higher in aspartame solutions than in sucrose solutions despite the fact that aspartame showed Cu‐complex capacity in solution.

Potentiometric flow injection determination of total water hardness in tap water by using cupric ion buffer.

A rapid and simple flow injection method for the determination of total water hardness using a cupric ion buffer and a flow-through type cupric ion selective electrode detector is proposed. The flow injection system was constructed with three stream channels. A sample solution of calcium or magnesium ion (200μl) was injected into a carrier (water) stream and was merged with a stream of 0.5 M sodium nitrate solution to maintain a constant ionic strength in the sample. This mixed stream was merged with the stream of cupric ion buffer solution consisting of 5×10-3 M cupric nitrate and 1×10-2 M EDTA adjusted to pH 9.4. The calcium or magnesium ion formed a complex with EDTA. In the reaction coil (0.5 mm i.d.×5.4 m) decreasing the concentration of EDTA in the buffer and as a result liberating the cupric ion from the EDTA-cupric ion complex. The change in the concentration of the free cupric ion was monitored with the cupric ion selective electrode and the concentration of the calcium or magnesium ion could be determined from the peak height of the electrode response. In order to make the sensitivity to the calcium ion equal to that to the magnesium ion, the pH of the cupric ion buffer was adjusted to pH 910 for determination of total water hardness. In this pH region, the amounts of EDTA reacted with the calcium and magnesium ions are almost the same and thus the change in the free cupric ion concentration is almost the same. A small amount of triethylenetetramine was added to the cupric ion buffer to suppress the effect of the chloride or bromide ion coexisting in the sample. The present method was successfully applied to determination of total water hardness in tap water with a sampling of 30 h-1 and a relative standard deviation of 0.7%. The results obtained by the proposed method were in good accordance with those obtained by the conventional chelate titration method.

Copper binding by dissolved organic matter: I. Suwannee River fulvic acid equilibria

A cupric ion-selective electrode measured free Cu in solutions of Suwannee River fulvic acid (FA) in a series of 30 titrations carried out both at variable and at constant (5.14, 7.00, 8.44) pH. Total Cu varied 0.1–100 μM, dissolved organic carbon (DOC) 1–10 mg C/l, Ca and Mg 0–10 mM, and ionic strength 0.005–0.1. Copper complexation by FA is first order in DOC for 1–10 mg C/liter, and variable-order in pH. Increasing Ca ++ or Mg ++ from 0 to 10 mM slightly increases Cu ++ activity, while increasing ionic strength from 0.005 to 0.1 significantly increases Cu ++ activity. An empirical N- site model was calibrated using a pooled set of six titrations with varying pH and DOC. Five binding components of varying proton dependence predict Cu binding by FA over a range of pH, DOC and total Cu in two verification tests of the model parameters. Parameters in this and other models tested are only empirical constructs.

Specificity of the ion exchange/atomic absorption method for free copper(II) species determination in natural waters

Concentrations of the free copper(II) species (Cu/sup 2 +/) measured by the ion exchange/atomic absorption (IEX) method in the presence of various concentrations of the ligands citrate, glycinate, phthalate, salicylate, chloride, and fulvate are compared to concentrations measured with a cupric ion selective electrode (ISE) and/or to concentrations calculated from known metal-ligand formation constants. The IEX method is considerably more sensitive for Cu/sup 2 +/ than the ISE method but is subject to interference from cationic and neutral copper complexes as well as from filterable colloids copper-hydroxo species at higher pH values. Accurate values of Cu/sup 2 +/ concentration are obtained by both methods in the presence of anionic copper-ligand complexes. Since fulvate, which is the principal ligand present in natural freshwaters, forms anionic copper complexes, the IEX method possesses adequate selectivity for measuring Cu/sup 2 +/ at trace levels in such waters. The complexing capacity of an acidic lake water with a very low dissolved organic carbon content was measured as 3.0 x 10/sup -8/ M by monitoring Cu/sup 2 +/ concentration by the IEX method during titration with copper nitrate.

Determination of Biuret in Urea and Mixed Fertilizers by Cupric Ion Selective Electrode

Abstract A method for determining biuret in urea and mixed fertilizers by using a cupric ion selective electrode (CISE) has been developed to take advantage of the simplicity of the apparatus. The method is based on the same principle as the atomic absorption spectrophotometric (AAS) method, 2.091-2.093: formation of a biuret-copper complex, elimination of excess copper, and determination of complexed copper. However, some changes were needed to eliminate starch and alcohol interferences. The method was tested for ruggedness and then compared with the AAS method for 4 fertilizer samples. Averages and variances were equivalent at the 99% confidence level according to t- and F-tests. A collaborative study is recommended to compare behavior of both methods in different laboratories.

Complexation of copper by aquatic humic substances from different environments

The copper-complexing properties of aquatic humic substances isolated from eighteen different environments were characterized by potentiometric titration, using a cupric ion selective electrode. Potentiometric data were analyzed using FITEQL, a computer program for the determination of chemical equilibrium constants from experimental data. All the aquatic humic substances could be modelled as having two types of Cu(II)-binding sites: one with K equal to about 10 6 and a concentration of 1.0 ± 0.4 × 10 −6 M(mg C) −1 and another with K equal to about 10 8 and a concentration of 2.6 ± 1.6 × 10 −7 M(mg C) −1. A method is described for estimating the Cu(II)-binding sites associated with dissolved humic substances in natural water based on a measurement of dissolved organic carbon, which may be helpful in evaluating chemical processes controlling speciation of Cu and bioavailability of Cu to aquatic organisms.

Determination of Zinc with Cupric Ion-Selective Electrode and its Analytical Application in Fertilizers

Determination of Zinc with Cupric Ion-Selective Electrode and its Analytical Application in Fertilizers

A note on the polarographic behavior of the Cu(II) ion selective electrode in seawater

The non-Nernstian behavior of a solid-state cupric ion-selective electrode in seawater is attributed to a reduction of Cu 2+ at the surface in accordance with a suggestion made in the literature. This ‘polarographic’ behaviour was demonstrated by showing that the electrode potential is affected by molecular oxygen in solution.

The Potential Response Of Copper(Ii) Sulfide Ion Selective Electrode To Hg(Ii) Ions In Aqueous Solution

Abstract The application of a cupric ion-selective electrode with a membrane of mixed Ag2S-CuS to measure the activity of Hg(II) is presented. The linear electrode response curve which covers near three decades, from 10−5 to 10−2 mol dm−3, of mercuric concentration range was obtained, under background of acetate buffer.

Cupric ion-selective electrode and inorganic cationic complexes of copper

Cupric ion-selective electrode and inorganic cationic complexes of copper