Cadmium Ion-selective Electrode Research Articles

A novel ion- selective electrode sensor based on crafted polymer sugar thia crown ether for the determination of Cadmium (II)

A Cadmium (II) ion-selective electrode (ISE) based on Thia polymeric crown ether (SPCE-Cd2+) as a membrane carrier in a PVC matrix was successfully built for the determination of Cd2+ ions. Using Dimethyl phthalate (DMP) plasticizer, the electrode showed a Nernstian liner response spanning the range of 1*10-1 to 1*10-7 M with a slope of (28) ±2 mV per decade charge and a detection limit of 1*10-9 M. The sensor has a 10-second response time. The cadmium ion-selective electrode is highly precise in its selectivity for Cd2+ over other cations. Some alkali and transition metal ions have selectivity coefficients in the range of 1 * 10-7 to 1 * 10-1. It worked well as an indicator electrode in the potentiometric measurement of the cadmium ion.

Metal sulfide quantum dots-aggregated PAMAM dendrimer for cadmium ion-selective electrode-based immunoassay of alpha-fetoprotein

An ion-selective electrode (ISE)-based immunoassay has been innovatively designed for the sensitive detection of liver cancer biomarker (alpha-fetoprotein, AFP), using metal sulfide quantum dot (QD)-based nano labels. CdS QDs-aggregated PAMAM dendrimer (QD-DE) was first synthesized and functionalized with polyclonal rabbit anti-human AFP antibodies. Thereafter, a sandwich immunoreaction was implemented on monoclonal mouse anti-human AFP antibody-coated microplate by using antibody-functionalized QD-DE as the secondary antibody. Accompanying the immunocomplex, subsequent potentiometric detection of cadmium ion dissolved from the QD-DE under acidic condition was conducted on a portable cadmium ion-selective electrode (Cd-ISE). Results revealed that the electrode potential of the Cd-ISE increased with the increment of AFP concentration from 0.1 to 100 ng mL−1 at a detection limit (LOD) of 68 pg mL−1. The relative standard deviations (RSD) were below 9.09% and 10.54% for the intra- and inter-assay, respectively. Additionally, six human serum specimens were determined on Cd- ISE-based immunosensor by using commercial human AFP ELISA kit as the reference, and gave good relationship between two methods. Importantly, Cd-ISE-based immunoassay offers the promise for simple and cost-effective screening of disease-related biomarkers.

Potentiometric determination of cadmium using coated platinum and PVC membrane sensors based on N,N′-bis(salicylaldehyde)phenylenediamine (salophen)

The construction and performance characteristics of novel PVC membrane (PME) and coated platinum (CPtE) cadmium ion selective electrodes based on N,N′-bis(salicylaldehyde)phenylenediamine (salophen) are described. The electrodes exhibit linear responses along with near Nernstian slopes of 28.9 ± 0.4 (PME) and 29.2 ± 0.6 (CPtE) mV/decade of concentration within the Cd2+ ion concentration range of 5.7 × 10−8 to 3.7 × 10−3 M for PME and 3.0 × 10−8–3.0 × 10−3 M for CPtE. These sensors are applicable in a pH range of 2.5–7.5. The lower detection limits by PME and CPtE are 3.2 × 10−8 and 1.6 × 10−8 M, respectively. They have a response time less than 14 s and can be used practically for a period of at least 2 months without any measurable divergence in results. The electrode can also tolerate partially non-aqueous media (ethanol, methanol and acetone) up to 30%. The electrodes showed excellent selectivity towards Cd2+ ion over a wide range of alkali, alkaline earth, and transition metals ions. They were successfully applied to the direct determination of Cd2+ ions in tap water, aqueduct water, and river water and soil sample. In addition the electrodes were used as an indicator electrode in potentiometric titration of Cd2+ ion with EDTA.

Solid contact cadmium ion-selective electrode based on ionic liquid and carbon nanotubes

A new type of cadmium ion-selective electrode with solid contact with the implementation of multi-walled carbon nanotubes (MWCNTs) as the ion-to-electron transducer and ionic liquid: 1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6) as a lipophilic ionic additive was reported. The proposed electrode exhibits low detection limit and short response time but has stable, reproducible and reversible potential. The presence of the interfacial water film was evaluated by the potentiometric water layer test and electrical properties of the membrane were studied by electrochemical impedance spectroscopy.

Urea Assisted Synthesis of Flower Like CuO Nanostructures and Their Chemical Sensing Application for the Determination of Cadmium Ions

AbstractThe novel nanostructures of CuO with improved morphology are strongly required for the development of devices with enhanced performance. In this study flower like nanostructures of CuO are synthesized by hydrothermal method using urea as tuning material for the morphology of CuO during the growth process. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques were used for the characterization of these nanostructures. The nanostructures are highly dense, uniform and well aligned on the gold coated glass substrate. Moreover, CuO nanostructures exhibited pure phase of CuO. These novel CuO nanostructures were potentially used for the construction of cadmium ion sensor by functionalizing with tetrathia‐12‐crown‐4 a selective cadmium ion ionophore. The proposed cadmium ion sensor has detected the wide range of cadmium ion concentrations from 1.0×10−9–1.0×10−1 M with a sensitivity of 29.3±0.3 mV/decade and also a fast response time of less than 10.0 s is demonstrated. CuO nanostructures based cadmium ion selective electrode has also shown excellent reproducibility, repeatability, selectivity, and stability. The sensor electrode was also used as indicator electrode for the confirmation of practical utility and the obtained result describes the good behavior of the sensor in the potentiometric titration for the determination of cadmium ions.

Measurement of Cadmium Ion in the Presence of Metal-Binding Biopolymers in Aqueous Sample

In aqueous environment, water-soluble polymers are effectively used to separate free metal ions from metal-polymer complexes. The feasibilities of four different analytical techniques, cadmium ion-selective electrode, dialysis sack, chelate disk cartridge, and ultrafiltration, in distinguishing biopolymer-bound and nonbound cadmium in aqueous samples were investigated. And two different biopolymers were used, including bovine serum albumin (BSA) and biopolymer solution extracted from cultivated activated sludge (ASBP). The ISE method requires relatively large amount of sample and contaminates sample during the pretreatment. After the long reaction time of dialysis, the equilibrium of cadmium in the dialysis sack would be shifted. Due to the sample nature, chelate disk cartridge could not filter within recommended time, which makes it unavailable for biopolymer use. Ultrafiltration method would not experience the difficulties mentioned above. Ultrafiltration method measuring both weakly and strongly bound cadmium was included in nominally biopolymer-cadmium complex. It had significant correlation with the Ion-selective electrode (ISE) method (R 2 = 0.989 for BSA, 0.985 for ASBP).

Ion imprinted polymer based potentiometric sensor for the trace determination of Cadmium (II) ions

A cadmium (II) ion selective electrode (ISE) based on an ion-imprinted polymer (IIP) as a novel ionophore has been prepared and studied. The ion-selective electrode (ISE) was prepared by dispersing cadmium (II) IIP particles in 2-nitrophenyloctyl ether as a plasticizer and then embedding them in a polyvinylchloride polymeric matrix. The Cd(II) ISE showed a nernstian response for cadmium (II) over the dynamic concentration range of 2.0×10−7–1.0×10−2molL−1, with a slope of 29.9mV per decade. The limit of detection was 1.0×10−7M. The proposed electrode revealed good selectivity over a wide variety of other cations including alkali, alkaline earth, heavy and transition metals. The accuracy of the proposed electrode was checked through the analysis of spiked water samples.

Ionic Liquids Improve Analytical Parameters of Cadmium Ion-Selective Electrodes with Solid Contact

Ionic Liquids Improve Analytical Parameters of Cadmium Ion-Selective Electrodes with Solid Contact

A Comparative Study of Cadmium Ion‐Selective Electrodes with Solid and Liquid Inner Contact

AbstractA comparative study was performed between three types of cadmium ion selective electrodes: solid contact electrode containing membrane doped with ionic liquid: 1‐alkyl‐3‐methylimidazolium chloride, solid contact electrode containing membrane doped with traditional lipophilic additive potassium tetrakis (p‐chlorophenyl) borate (KTpClB) and the classical cadmium‐ion selective electrode with internal filling solution. The basic analytical parameters of the studied electrodes, such as the slope characteristic, the detection limit, response time, lifetime, selectivity coefficients against lead, nickel, cobalt, zinc, magnesium, strontium, calcium, potassium and sodium ions as well as the dependence of the electrode potential on pH were determined. The best results were obtained for an electrode with solid contact based on ionic liquid 1‐ethyl‐3‐methylimidazolium chloride.

Binding of cadmium to soil humic acid as a function of carboxyl group content

The binding of Cd(II) to soil humic acid (HA) at pH 6.5 and in 0.1 mol/L KNO3 ionic medium, was studied by potentiometric titration with a cadmium ion selective electrode. The influence of carboxyl groups in cation-humic interactions was investigated by selective blocking of humic acid carboxyl groups with thionyl chloride and methanol. Infrared spectroscopic analysis confirmed that esterification took place. Differences between underivatized and derivatized HA complexation properties are ascribed to carboxyl groups. The Scatchard plots and incremental formation constants were used to obtain values for Cd-binding constants, for both HAs. The derivatization decreased the number of HA complexing sites by approximately 60 %, which correlates with acid-base properties of both HAs, studied by barium hydroxide and calcium acetate exchange methods. The stability constants for binding at the strongest sites (logKINT) was larger for underivatized HA (5.40) than for derivatized HA (4.92), indicating greater stability in the case when carboxyl groups are involved in complexation reaction.

A polyvinylchloride-based cadmium ion-selective electrode using [Mo2(OAc)2(H2-calix[4]arene)] as an electroactive material

A highly electroactive material [Mo₂(OAc)₂(H₂-calix[4]arene)] is used as a neutral carrier for Cd²+ ions in this paper. The membrane is fabricated by using ionophore [Mo₂(OAc)₂(H₂-calix[4]arene)]:poly(vinyl chloride) (PVC): dibutylphthalate(DBP):sodium tetraphenyl borate (NaTPB) in the ratio of 40:300:470:5 respectively and tetrahydrofuran (THF) used as a solvent. The membrane electrode performed in the concentration range of 9.9 x 10⁻⁸-1.0 x 10⁻¹ M (2.34 x 10⁻⁵-23.64 mg/mL) having the Nernstian slope of 30.0±1.0 mV and the best detection limit was observed at 9.8 x 10⁻⁸ M (2.31 x 10⁻⁵ mg/mL). The proposed membrane electrode has the response time of 12 s and a useful working pH range of 1.0-7.0, and used over a period of 10 months and work satisfactorily in the test solution having 30% (v/v) non-aqueous content. Electrode sensor has distinguishable ability for Cd²+ ion with regard to several alkali, alkaline earth, transition and heavy metal ions. It was used in direct potentiometry as an indicator electrode, in the potentiometric titration of 10⁻³ M Cd²+ solution against 10⁻² M of ethylenediaminetetraacetic acid (EDTA).

A System for High Temporal Resolution of Cadmium Uptake in Plants

Flowing culture systems have been widely used in plant research to answer numerous questions involving plant nutrient requirements, cycles, and kinetics. Here, a flowing culture system was built in order to detect cadmium uptake in plants. Termed the Experimental Cadmium Uptake Detection System (ECUDS), it featured an automated valve system, computer-based data acquisition and control, and real-time data display. The system was designed for detection of cadmium uptake with relatively high temporal resolution. System cadmium level was measured by a cadmium ion-selective electrode (ISE). Additional system parameters, such as solution pH, could be measured as well. This article reports on the design, testing, and validation of ECUDS with Brassica napus, an agronomic plant with potential for use in environmental cleanup.

Direct Potentiometry of Polyacrylate with Solid-Membrane Cadmium Ion-Selective Electrode

Three solid-state ISEs (Cd, Pb, Cu) were evaluated for direct potentiometry of polyacrylate. Cd-ISE had a lower pH response but an appreciably high response to PA, while Cu-ISE had a remarkably high pH response but a rather low response to PA. Pb-ISE showed intermediate behaviors. These results suggest direct potentiometry of PA by simultaneous measurements of pH and the Cd-ISE response. Anions of foreign salts may cause positive errors by the interactions with Cd2+, whereas cations of salts may cause negative errors by the interactions with PA. The extent of such errors is, however, negligible in the detection of PA in the circulating water of cooling systems.

Estudo da capacidade de complexação e sua relação com algumas variáveis ambientais em cinco represas do Rio Tietê/Brasil

The copper and cadmium complexation properties in natural sediment suspensions of reservoirs of the Tiete River were studied using the solid membrane copper and cadmium ion-selective electrodes. The complexation and the average conditional stability constants were determined under equilibrium conditions at pH=6.00 ± 0.05 in a medium of 1.0 mol L-1 sodium nitrate, using the Scatchard method. The copper and cadmium electrodes presented Nernstian behavior from 1x10-6 to 1x10-3 mol L-1 of total metal concentration. Scatchard graphs suggest two classes of binding sites for both metals. A multivariate study was done to correlate the reservoirs and the variables: complexation properties, size, total organic carbon, volatile acid sulfide, EII and pH.

Full-wave analysis of stripping chronopotentiograms at scanned deposition potential (SSCP) as a tool for heavy metal speciation: Theoretical development and application to Cd(II)-phthalate and Cd(II)-iodide systems

A new mathematical treatment has been developed and implemented in an EXCEL spreadsheet in order to determine average equilibrium functions from the full set of data measured by scanning stripping chronopotentiometry (SSCP) in solutions containing different proportions of heavy metal ions and small-sized ligands. It has been applied to the experimental systems Cd(II)-phthalate and Cd(II)-iodide as models of complexation in the absence and in the presence of electrodic adsorption, respectively. The good agreement between the complexation parameters determined in this way, those predicted from literature data and those obtained using a cadmium ion selective electrode (ISE) confirms the validity of the proposed methodology and encourages its further refining for the analysis of macromolecular and heterogeneous systems.

Cadmium(II) ion selective electrode based on pyridine-3-carboxyaldehyde thiosemicarbazone

A new polyvinyl chloride (PVC) membrane electrode based on pyridine-3-carboxyaldehyde thiosemicarhazone was prepared using 2-nitrophenyl-octyl ether as plasticizer lor Cd I I selective sensor. The sensor exhibits a Nernstian response for Cd I I ion over a wide concentration range (5 x 10 - 2 -2 x 10 - 5 M). The electrode assembly works between pH 2.5-7.0, exhibits a response time of <20 s and performed satisfactorily over a period of 3-4 months with good reproducibility. The electrode exhibits excellent selectivity of the order of 10 - 3 over a number of bivalent cations and also demonstrates its utility as an indicator electrode in the potentiometric titration of Cd 2 + with EDTA.

Novel solid-state cadmium ion-selective electrodes based on its tetraiodo- and tetrabromo-ion pairs with cetylpyridinium

Two novel cadmium solid-state ion-selective electrodes have been prepared by coating the surface of a graphite rod electrode directly with tetrahydrofuran solution containing PVC, cetylpyridinium–tetraiodocadmate (I) or cetylpyridinium–tetrabromocadmate (II), dioctyl phthalate and sodium tetraphenyl borate. The two sensors exhibit near-Nernstian anionic slopes of −29.8 and −25.1 mV/concentration decade, independently of pH over a wide range, with very fast response times of 3 and 7 s, respectively. The tetraiodocadmate (TIC) and tetrabromocadmate (TBC) electrodes posses linear ranges of 1.5 × 10 −6–1 × 10 −1 and 1.0 × 10 −6–1 × 10 −1 M and lower detection limits (LDL) of 6 × 10 −7 and 8 × 10 −7 M, respectively. The effects of membrane composition, type of plasticizer and pH of the sample solution were investigated thoroughly. The TBC electrode is shown to be free of all interference that is common for most of the reported cadmium ISEs except for that of Hg 2+ ion. The two electrodes were applied for the determination of cadmium in some alloys and polluted water.

Cadmium ion-selective electrode based on tetrathia-12-crown-4

A new polyvinylchloride membrane sensor for Cd 2+ ions based on tetrathia-12-crown-4 as an ionophore was prepared. The sensor exhibits a Nernstian response for cadmium ions over a wide concentration range (4.0×10 −7 to 1.0×10 −1 M) with a slope of 29±1 mV decade −1. The limit of detection is 1.0×10 −7 M (0.01 ppm). It has a fast response time of <10 s and can be used for at least 6 weeks without any divergence in potential. The electrode can be used in the pH range from 2.5 to 8.5. The proposed sensor shows fairly good discriminating ability towards Cd 2+ ion in comparison with some alkali, alkaline earth, transition and heavy metal ions. It was successfully applied for the direct determination of Cd 2+ in solution and, as an indicator electrode, in potentiometric titration of cadmium ions.

Cadmium Ion-Selective Electrode Based on Cyanocopolymer

Cd2+ ion-selective electrode based on poly (styrene-co-acrylonitrile) copolymer (SAN) has been prepared using 8-hydroxyquinoline as an electroactive ionophore and dibutylphthalate as a plasticizing agent. The Cd2+ ion-selective electrode in presence of sodiumtetraphenylborate (NaTPB) as an anion excluder has exhibited a linear response within 4.46×10–4–1.0×10–1 mol dm–3 activities of Cd2+ ions at a pH variation of 3.20 to 6.80. The observed response time of the prepared electrode was 12 seconds. The electrode has shown a reproducible Nernstian slope of 29 mV decade–1 activities of Cd2+ ions over a period of six months. The selectivity of the prepared electrode for Cd2+ ions in presence of a number of interfering cations is found to be high within the working range of the electrode. However, Pb2+, Cu2+ and Mg2+ ions have shown interference when the activities of the Cd2+ ions in the solution were less than 1×10–6 mol dm–3.The electrode sensitivity and working range were found to be dependent on the concentration of the plasticizer and ionophore used in the preparation of the membrane electrode. The electrode can be used as an indicator electrode for the potentiometric titration of Cd2+ ions using ethylenediamine tetraacetic acid (EDTA) as titrant.

Effect of concentration of ion exchanger, plasticizer and molecular weight of cyanocopolymers on selectivity and sensitivity of Cd(II) ion selective electrode

Potential response of cadmium(II) ion selective electrode based on cyanocopolymer matrices and 8-hydroxyquinoline as ionophore has been evaluated by varying the amount of ionophore, plasticizer and the molecular weight of the cyanocopolymer. The sensitivity, working range, response time, and metal ions interference have shown a significant dependence on the concentration of ionophore, plasticizer and molecular weight of cyanocopolymers. The electrodes prepared with 2.38×10 −2 mol kg −1 of ionophore, 1.23×10 −2 mol dm −3 of plasticizer and 2.0 g of cyanocopolymer (molecular wt., 59 365) have shown a Nernstian slope of 29.00±0.001 mV per decade activities of Cd 2+ ions with a response time of 12±0.007 s. Electrodes have shown an appreciable selectivity for Cd 2+ ions in the presence of alkali and alkaline earth metal ions and could be used in a pH range of 2.5–6.5. The cyano groups of the copolymers contributed significantly to enhance the selectivity of the electrode. The electrode has shown an appreciable average life of 6 months without any significant drift in the electrode potential and found to be free from leaching of membrane ingredients. Electrode response is explained considering phase boundary model based on thermodynamic considerations.