Copper Ion-selective Electrode Research Articles

Removal of copper contamination from simulated wastewater using chitosan and shrimp waste: Equilibrium analysis

This study addressed copper removal from aqueous solution using unprocessed shrimp tail shell waste (STW) with comparison to removal by chitosan derived from shrimp shell. The use of a copper ion selective electrode enabled continuous copper concentration measurement and determination of the STW mass-time relationship needed to achieve the USEPA Maximum Contaminant Level for copper as a function of adsorbent dose. Copper removal using chitosan produced a blue solid without surface morphology changes, consistent with an adsorption or ion exchange mechanism. Calcium carbonate in the STW was essential for copper removal by the formation of a green copper-containing deposit primarily on the exposed edges of the ground shrimp solids and an increase in calcium concentration and pH in the treated solution. The systems reached equilibrium over several days. Equilibrium data were fitted to the Freundlich, Langmuir, Temkin, Sips, and B-E-T isotherms and the Freundlich model fit the data well. Raw STW, cooked STW, and chitosan with particle sizes ranging from 425 to 850 µm gave a maximum copper loading of 184 mg/g, 170 mg/g, and 129 mg/g, respectively. Both raw and cooked STW had higher copper capacities than commercial chitosan and provide a low cost and environmentally friendly adsorbent. Comparison of small particle size (< 425 µm) adsorbents after six hours showed that raw STW had double the copper loading of chitosan. Small STW achieved greater than 97.4% copper removal from a 50 mg/L copper solution and reached the MCL in less than one hour for 1.5 g/L loadings.

Copper ion-selective electrodes based on newly synthesized salen-type Schiff bases and their complexes

Copper ion-selective electrodes based on newly synthesized salen-type Schiff bases and their complexes

Revised application of copper ion selective electrode (Cu-ISE) in marine waters: A new meta-calibration approach

Copper (Cu) is a bio-essential trace element that is of concerns due to its potential toxicity at concentrations commonly encountered in coastal waters. Here, we revisit the applicability of Cu(II) ion selective electrode (Cu-ISE) based on a jalpaite membrane for the measurement of Cufree in seawater. At high total Cu concentration (>0.1 mM), (near)Nernstian slope was obtained and determination of Cufree down to fM levels was possible. However, this slope decreases with decreasing total Cu concentration (e.g. 7 mV/decade at 15 nM total Cu) making the use of a common single calibration approach unreliable. To solve this problem, we carried out several calibrations at different levels of total Cu (15 nM - 1 mM) and ethylenediamine (EN: 5 μM - 15 mM) and fitted the calibration parameters (slope and intercept) as a function of total Cu using the Gompertz function (a meta-calibration approach). The derived empirical equations allowed the determination of Cufree at any total Cu concentration above 20 nM (determination of Cufree at lower total Cu levels is prevented by the dissolution of the electrode). We successfully tested this meta-calibration approach in UV digested seawater in presence of a synthetic ligand (EN), isolated natural organic matter (humic acid, HA) and in a natural estuarine sample. In each case, our meta-calibration approach provided a good agreement with modeled speciation data (Visual MINTEQ), while standard single approach failed. We provide here a new method for the direct determination of the free Cu ion concentration in seawater at levels relevant for coastal waters.

An integrated all-solid-state screen-printed potentiometric sensor based on a three-dimensional self-assembled graphene aerogel

An integrated all-solid-state screen-printed ion-selective potentiometric sensor for the determination of Cu2+ is proposed. The whole-cell potentiometric sensor incorporates a polymeric membrane copper ion-selective electrode (Cu2+-ISE) as an indicator electrode and an Ag/AgCl reference electrode with a polyvinyl butyral reference membrane. The three-dimensional (3D) self-assembled porous graphene aerogel (PGA) can be conveniently and rapidly electrodeposited on the electrode substrate surface. Due to its interior 3D interconnected porous structures, the PGA has a large electrical double layer capacitance and fast charge transfer capability, which make it promising to be used as solid contact for the fabrication of the Cu2+-ISE. The developed potentiometric sensor shows a good Nernstian response over a range from 10−6 to 10−3 M with a detection limit of 10−6.5 M. In addition, the sensor exhibits a stable potential response with the absence of an undesirable water layer at the ion-selective membrane/PGA interface.

Phytic acid-based copper(ii) ion-selective electrode on graphene oxide for potentiometric immunoassay of breast cancer antigen 15-3

A potentiometric immunoassay based on a copper(ii) ion-selective electrode (Cu-ISE) was designed for the quantitative determination of carbohydrate antigen 15-3 (CA 15-3; a tumor marker associated with breast cancer).

Copper nanocluster-labeled hybridization chain reaction for potentiometric immunoassay of matrix metalloproteinase-7 in acute kidney injury and renal cancer

A simple and portable potentiometric immunoassay was designed for the quantitative detection of matrix metalloproteinase-7 (MMP7) in acute kidney injury and renal cancer on a copper ion-selective electrode (Cu-ISE).

Potentiometric Characterization of Telomerase Activity Using a Copper(ii)-pyrophosphate Complex with a Copper ion-selective Electrode

A novel potentiometric sensing platform was designed for real-time electronic monitoring of telomerase activity using a copper(II) ion-selective electrode (Cu-ISE). The target-induced coordination of pyrophosphate ion with copper ion (Cu2+) was utilized for the detection of the enzyme activity. Upon telomerase introduction, a DNA primer was elongated in the presence of deoxyribonucleoside triphosphates, accompanying formation of the by-product (pyrophosphate ion; P2O74-). The generated pyrophosphate ions chemically coordinated with free copper ions to form the copper(II)-pyrophosphate complex, thereby resulting in a decrease in the number of free copper ions present in solution. With the addition of telomerase, the electrode potential on the Cu-ISE increased relative to the background signal. The results indicated that the copper(II)-pyrophosphate system exhibited good potentiometric response for the detection of telomerase activity, and allowed the determination of the analyte in HeLa cell extract at concentrations as low as 36 cells mL−1. Moreover, the Cu-ISE-based sensing platform afforded good reproducibility, thus representing a useful approach for practical use in quantitative telomerase activity assays.

Rapid Monitoring of Copper Over a Wide Concentration range by High-Sensitive Potentiometric Membrane Electrode Based on 1-cyano-1-piperidino-2(N- piperidino methyl)-cyclo hexane

n this paper, 1-cyano-1-piperidino-2(N- piperidino meth-yl)-cyclohexane was synthesized. The lowest-energy conformer of this molecule (Ligand) with axial and equatorial forms of cyanide toward cyclohexane and local minima corresponding to their complexes with various ions were obtained using Monte Carlo procedure by Molecular Mechanics with MMFF94 method. The calculated results of the Gibbs free energy of the reaction using density functional theory (DFT) show that the thermodynamic reactivity of complexation of copper ion with studied ligand is the best. Finally, a selective and sensitive copper-ion selective liquid membrane electrode for potentiometric monitoring of ultra-trace amounts of Cu2+ was prepared by using 1-cyano-1-piperid-ino-2(N- piperidino methyl)-cyclohexane as an excellent ionophore. This electrode exhibits a Nernstian response for Cu2+ ions over a con-centration range (1.5 × 10-2 to 1.0 × 10-8 mol L-1) with a slope of 28.4±0.4 mV per decade. The limit of detection of the sensor is 6.3 × 10-9 mol L-1. The sensor has a relatively fast response time (&lt;10 s) and a useful working pH range of 5.0–8.5. Interference of some cations was also evaluated. The practical utility of the Cu2+ ion sensor has been demonstrated by using it as an indicator electrode in potentiomet-ric titration of Cu2+ with EDTA and for direct determination of Cu2+ in well water samples.

Determination of copper(II) ion in food using an ionic liquids-carbon nanotubes-based ion-selective electrode

In this work, a copper(II) ion-selective electrode with an ionic liquid (IL), 1-(2-aminoethyl)-3-butylimidazolium bis(trifluoromethanesulfonyl)imide ([C4NH2C2im]NTf2), as active material has been developed. Parameters affecting the performance of the electrode, such as the dosage of the ILs, the amount of carbon nanotubes, and aqueous pH values, were investigated. The experimental results indicated that the optimal composition of the electrode filling material was 47.6% [C4NH2C2im]NTf2, 47.6% tetrabutylphosphonium bis(trifluoromethanesulfonyl)imide (TBPNTf2) and 4.8% carboxylic multi-walled carbon nanotubes (MWCNTs-COOH). Under the optimal conditions, the developed electrode exhibited a good linear response over the concentration range of 10−10–10−5molL−1 and had a low limit of detection, 7.9×10−11molL−1. No obvious interference from common metal ions was found. The proposed electrode was applied to determine copper (II) ion in food samples and the results were comparable to graphite furnace atomic absorption spectrometry (GF-AAS).

Quantitative Determination of NTA and Other Chelating Agents in Detergents by Potentiometric Titration with Copper Ion Selective Electrode.

Quantitative analysis of nitrilotriacetate (NTA) in detergents by titration with Cu2+ solution using a copper ion selective electrode was achieved. This method tolerates a wide range of pH and ingredients in detergents. In addition to NTA, other chelating agents, having relatively lower stability constants toward Cu2+, were also qualified with sufficient accuracy by this analytical method for model detergent formulations. The titration process was automated by automatic titrating systems available commercially.

Combination of a Copper-Ion Selective Electrode and Fluorometric Titration for the Determination of Copper(II) Ion Conditional Stability Constants of Humic Substances.

A fluorescence quenching model using copper(II) ion (Cu(2+)) ion selective electrode (Cu-ISE) is developed. It uses parallel factor analysis (PARAFAC) to model fluorescence excitation-emission matrices (EEMs) of humic acid (HA) samples titrated with Cu(2+) to resolve fluorescence response of fluorescent components to Cu(2+) titration. Meanwhile, Cu-ISE is employed to monitor free Cu(2+) concentration ([Cu]) at each titration step. The fluorescence response of each component is fit individually to a nonlinear function of [Cu] to find the Cu(2+) conditional stability constant for that component. This approach differs from other fluorescence quenching models, including the most up-to-date multi-response model that has a problematic assumption on Cu(2+) speciation, i.e., an assumption that total Cu(2+) present in samples is a sum of [Cu] and those bound by fluorescent components without taking into consideration the contribution of non-fluorescent organic ligands and inorganic ligands to speciation of Cu(2+). This paper employs the new approach to investigate Cu(2+) binding by Pahokee peat HA (PPHA) at pH values of 6.0, 7.0, and 8.0 buffered by phosphate or without buffer. Two fluorescent components (C1 and C2) were identified by PARAFAC. For the new quenching model, the conditional stability constants (logK1 and logK2) of the two components all increased with increasing pH. In buffered solutions, the new quenching model reported logK1 = 7.11, 7.89, 8.04 for C1 and logK2 = 7.04, 7.64, 8.11 for C2 at pH 6.0, 7.0, and 8.0, respectively, nearly two log units higher than the results of the multi-response model. Without buffer, logK1 and logK2 decreased but were still high (>7) at pH 8.0 (logK1 = 7.54, logK2 = 7.95), and all the values were at least 0.5 log unit higher than those (4.83 ~ 5.55) of the multi-response model. These observations indicate that the new quenching model is more intrinsically sensitive than the multi-response model in revealing strong fluorescent binding sites of PPHA in different experimental conditions. The new model was validated by testing it with a mixture of two fluorescing Cu(2+) chelating organic compounds, i.e., l-tryptophan and salicylic acid mixed with one non-fluorescent binding compound oxalic acid titrated with Cu(2+) at pH 5.0.

A new technique for online measurement of total and water-soluble copper (Cu) in coarse particulate matter (PM)

This study presents a novel system for online, field measurement of copper (Cu) in ambient coarse (2.5–10 μm) particulate matter (PM). This new system utilizes two virtual impactors combined with a modified liquid impinger (BioSampler) to collect coarse PM directly as concentrated slurry samples. The total and water-soluble Cu concentrations are subsequently measured by a copper Ion Selective Electrode (ISE). Laboratory evaluation results indicated excellent collection efficiency (over 85%) for particles in the coarse PM size ranges. In the field evaluations, very good agreements for both total and water-soluble Cu concentrations were obtained between online ISE-based monitor measurements and those analyzed by means of inductively coupled plasma mass spectrometry (ICP-MS). Moreover, the field tests indicated that the Cu monitor could achieve near-continuous operation for at least 6 consecutive days (a time resolution of 2–4 h) without obvious shortcomings.

A Potentiometric Study of the Association of Copper(II) and Sulfate Ions in Aqueous Solution at 25 °C

A study of the association between copper(II) and sulfate ions in aqueous solution has been made using copper ion-selective electrode potentiometry at constant ionic strengths (I) of 0.05, 0.1, 0.25, 0.5, 1.0, 3.0 and 5.0 mol·L−1 in NaClO4 media at 25 °C. Only one complex was detected, corresponding to the equilibrium: \( {\text{Cu}}^{ 2+ } ({\text{aq}}) + {\text{SO}}_{4}^{2 - } ({\text{aq}}) \rightleftarrows {\text{CuSO}}_{4}^{0} ({\text{aq}}). \) No higher order complexes were detected even at sulfate/copper(II) concentration ratios of up to 1,000. The present potentiometric values of log10K1(I) are shown to be consistently higher than those obtained by UV–Vis spectrophotometry because of the failure of the latter technique to detect all of the solvent-separated ion pairs present. Extrapolation of log10K1(I) to infinite dilution using an extended Guggenheim equation yielded a standard state value of log10\( K_{1} \{ {\text{CuSO}}_{4}^{0} ({\text{aq}})\} = 2.32 \pm 0.09 \), which is in excellent agreement with a recent IUPAC-recommended value.

Application of ionic liquid to the construction of Cu(II) ion-selective electrode with solid contact

The potentiometric properties of copper ion-selective electrodes (ISEs) with solid contact based on polymeric membrane were investigated. Ionic liquids (ILs), alkylmethylimidazolium chlorides are used for the electrode construction as transducer media. The addition of ionic liquid to the membrane phase was found to improve the analytical parameters of the studied electrodes. The best results were obtained for electrode having membrane doped with 1-ethyl-3-methyl imidazolium chloride. The electrode shows a Nernstian response for copper ions over a wide concentration range (1×10−7–1×10−1molL−1) and the slope of 28.9mVdecade−1. The limit of detection is 3.2×10−8molL−1. It has a fast response time of 5–10s and can be used for more than 4 months without any divergence in potential. The proposed sensor is not pH sensitive in the range 2.5–6.0 and shows a very good discriminating ability towards Cu2+ ion in comparison with some alkali, alkaline earth, transition and heavy metal ions. Moreover, it characterizes by high potential stability, reproducibility and fully repeatability.

Complex-forming properties of peat humic acids from a raised bog profiles

Humic substances (HS) belong to the most powerful complex-forming agents, significantly affecting major and trace element speciation in natural environment. Several authors have focused on humic–metal interactions, using differing methods and comparing humic substances on different sources. However, the intrinsic differences among the HS of different origin and the impact of humification degree on the complex formation between humic substances and metals have not received the necessary attention until now.The aim of this study is to determine the Cu(II) complexing capacity and stability constants of Cu(II) complexes of humic acids (HA) isolated from two well-characterized raised bog peat profiles in respect to the basic properties and humification characteristics of the studied peats and their humic acids. Elemental and functional analysis of the isolated HA were determined by elemental composition (C, H, N, O), UV spectrophotometry, and the total acidity method, as well as the copper (Cu2+) ion selective electrode was used in complexing analysis of humic acids and metal ions.The complex stability constants are within the range of stability constants of the humic substances isolated from other sources (soil, coal, water, and peat). The complex stability constants significantly changed within the bog profiles and are well correlated with the age and the degree of peat decomposition.A comparison of the complex stability constant and the actual copper concentration in peat humic acids shows significant correlation, indicating the importance of tight metal binding for the actual presence of metal in peat and peat humic acids. None of the basic characteristics of humic acids (concentration of carboxylic groups and total acidity, hydrophobicity, etc.) alone can fully explain the complex-forming capacity of humic acids, which suggests a contribution of other factors that are yet to be determined.

Kinetics and equilibrium properties of the biosorption of Cu2+ by algae

The purpose of this study was to examine the kinetics and equilibrium properties of freshwater algae with Cu(2+). This was a model system to explore using algae as biosensors for water quality. Methods included making luminescence measurements (fluorescence) and copper ion-selective electrode (CuISE) measurements vs. time to obtain kinetic data. Results were analyzed using a pseudo-first-order model to calculate the rate constants of Cu(2+) uptake by algae: k (p(Cu-algae)) = 0.0025 ± 0.0006s(-1) by CuISE and k (p(Cu-algae)) = 0.0034 ± 0.0011s(-1) by luminescence. The binding constant of Cu-algae, K (Cu-algae), was 1.62 ± 0.07 × 10(7)M(-1). Fluorescence results analyzed using the Stern-Volmer relationship indicate that algae have two types of binding sites of which only one appears to affect quenching. The fluorescence-based method was found to be able to detect the reaction of algae with Cu(2+) quickly and at a detection limit of 0.1mgL(-1).

Application of Ionic Liquid to the Construction of Cu(II) ion-selective Electrode with Solid Contact

Abstract Potentiometric properties of copper ion-selective electrodes (ISEs) with solid contact based on polymeric membrane were investigated. For the electrode construction ionic liquids (ILs), alkylmethylimidazolium chlorides are used as transducer media. The addition of ionic liquid to the membrane phase was found to improve the analytical parameters of the studied electrodes. The best results were obtained for electrode having membrane doped with 1-ethyl-3-methyl imidazolium chloride. The electrode shows a Nernstian response for copper ions over a wide concentration range (1x10-7-1x10-1 mol L-1) and the slope of 28.9 mV/decade. The limit of detection is 3.2x10-8 mol L-1. It has a fast response time of 5-10 s and can be used for more than 4 months without any divergence in potential. The proposed sensor is not pH sensitive in the range 2.5-6.0 and shows a very good discriminating ability towards Cu2+ ion in comparison with some alkali, alkaline earth, transition and heavy metal ions.

Development of a new copper(II) ion-selective PVC membrane electrode based on tris(2-benzimidazolylmethyl)amine

Development of a new copper(II) ion-selective PVC membrane electrode based on tris(2-benzimidazolylmethyl)amine

Lead(II) and copper(II) ion-selective electrodes based on two heterocyclic compounds

In this paper, two nitrogen, sulphur or oxygen containing heterocyclic compounds were used as ionophores in ion-selective electrodes. In these two ion-selective electrodes, 2,6-di(5-methyl-1,3,4-oxadiazol-5-yl)pyridine (DMOP) gives the best Pb2+ sensitivity and 2,5-di(2′-methylpyridinethio)thiadiazole (DPTD) gives the best sensitivity for Cu2+. These electrodes are composed of KTpClPB as anion excluder and DOS as plasticizer. The two membrane electrodes show Nernstian or near-Nernstian response towards Pb2+ or Cu2+ (29.3 and 27.3 mV/decade, respectively) over the concentration range 10−5∼10−2 and 10−6∼10−3 M, respectively. The response time was less than 20 sec and a good reproducibility over a period of 2 months was observed. The electrodes exhibited good selectivities over a number of alkali, alkaline earth and transition metal ions. The proposed electrodes have also been used for the direct determination of Pb2+ and Cu2+ ions in real samples.

Analytical determination of apparent stability constants using a copper ion selective electrode

Copper(II) complexes of di-, tri- and tetra peptides with previously published protonation constants were re-investigated using pH and copper ion selective electrode (ISE) potentiometry in conjunction with a modified version of HYPERQUAD computer program. The purpose was to demonstrate the suitability of the ISE approach for the determination of apparent stability constants for copper(II) complexes with ligands for which proton stability constants were not available. The interactions of Cu 2+ with oligopeptides were also analysed using surface enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-ToF-MS). The results provide an insight into the metal complex species formed, their apparent stabilities under selected conditions and the effect of the relative positions of certain amino acids within the peptide sequence.