Selective electrochemical sensor for copper (II) ion based on chelating ionophores

A facile synthesis of a novel 4-hydroxyl-3-azo coumarin based colorimetric probes for detecting Hg2+ and a fluorescence turn-off response of 3CBD to Fe3+ in aqueous environment

Two azo dyes, (E)-3-(benzo[d]thiazol-2-yldiazenyl)-4-hydroxy-2H-chromen-2-one (3CBD) and (E)-4-hydroxy-3-(quinolin-2-yldiazenyl)-2H-chromen-2-one (3CQD), were designed and synthesized using facile methods. The structures were validated through FTIR and NMR spectroscopy. The photophysical property analyses were further studied using UV-Vis and fluorescence spectrophotometers. Consequently, the absorption and emission spectra of 3CBD confirmed its selectivity of Hg2+ and turn-off response to Fe3+. On the other hand, the absorption spectra analysis of 3CQD demonstrated selectivity in the presence of Hg2+. The colorimetric investigations demonstrated a significant visual response specifically for Hg2+, enabling real-time analysis in the corresponding solutions. The presence of other coexisting metal ions does not interfere with the detection of the target metal ion. The fluorescence studies of the two probes revealed that 3CBD was highly fluorescent, which was significantly quenched by Fe3+, upon excitation at 340 nm. Utilizing Job plot analyses, it was determined that the complexes 3CBD-Hg2+ and 3CQD-Hg2+ exhibit a binding stoichiometry of 1 : 1. The association constants for these complexes were measured to be 7.48 × 105 and 9.12 × 105 M-1, respectively, indicating a strong association between both probes and their respective metal ions. Both chemosensors exhibited comparable limits of detection (LOD) and limits of quantification (LOQ) of 0.03 μM and 0.10 μM, respectively. Reversible studies confirmed that only chemosensor 3CQD could serve as a secondary sensor for EDTA. The theoretical studies calculated using Density Functional Theory (DFT) program at B3LYP/6-31G** (Spartan '10 package) level.

Construction of an optical sensor for copper determination in environmental, food, and biological samples based on the covalently immobilized 2-(2-benzothiazolylazo)-3-hydroxyphenol in agarose

An optical chemical sensor has been developed for the quantitative spectrophotometric analysis of copper. The optode is dependent on covalent immobilization of 2-(2-benzothiazolylazo)-3-hydroxyphenol (BTAHP) in a transparent agarose membrane. The absorbance variation of immobilized BTAHP on agarose as a film upon the addition of 5 × 10-3 M aqueous solutions of Mn2+, Zn2+, Hg2+, Cd2+, Pb2+, Co2+, Ni2+, Fe2+, La3+, Fe3+, Cr3+, Zr4+, Se4+, Th4+, and UO22+ revealed substantially higher changes in the Cu2+ ion content compared to other ions investigated here. The effects of various experimental parameters, such as the solution pH, the reaction time, and the concentration of reagents, on the quality of Cu2+ sensing were examined. Under ideal experimental circumstances, a linear response was achieved for Cu2+ concentrations ranging from 1.0 × 10-9 to 7.5 × 10-6 M with an R2 value of 0.9988. The detection (3σ) and quantification (10σ) limits of the procedure for Cu2+ analyses were 3.0 × 10-10 and 9.8 × 10-10 M, respectively. No observable interference was recorded in the detection of Cu2+ due to other inorganic cations. With no indication of BTAHP leaching, the membrane demonstrated good durability and quick response times. The optode was effectively used to determine the presence of Cu2+ in environmental water, food, and biological samples.

Potentiometric Determination of Moxifloxacin by Solid-Contact ISEs in Wastewater Effluents

In recent years, the use of ion-selective membranes in the sensing and assessment of environmental contaminants has become a critical goal. Using sodium tetraphenylborate (TPB) and phosphotungstic acid (PTA) as ion-pairing agents, two sensitive and selective sensors were manufactured to evaluate the electrochemical response of moxifloxacin hydrochloride (MOX). The optimal electrochemical behavior was attained by fine-tuning all assay parameters. The manufactured membranes’ performance was optimal in a pH range from 1.0 to 5.0 with a linearity between 1 × 10−6 M and 1 × 10−2 M. The MOX–TPB and MOX–PTA membrane electrodes have Nernstian slopes of 59.2 ± 0.60 mV/decade and 58.4 ± 0.50 mV/decade, respectively. The proposed method was used to determine MOX in its pure form as well as real pharmaceutical wastewater effluents. The fabricated electrodes were effectively applied for the sensitive and selective determination of MOX in actual wastewater effluents without the need for any pre-treatment processes.

Potentiometric Sensors for the Selective Determination of Benzodiazepine Drug Residues in Real Wastewater Effluents

The application of ion-selective electrodes (ISEs) in the detection and determination of environmental pollutants has become a very important mission in the last few years. Two selective and sensitive membrane electrodes were fabricated in the laboratory and intended to evaluate the electrochemical response of bromazepam (BRZ) using phosphotungstic acid (PTA) and sodium tetraphenylborate (TPB) as ion pairing agents. The linearity range of the fabricated electrodes was between 1 × 10−6 M to 1 × 10−3 M. Nernstian slopes of 54 mV/decade and 57 mV/decade were obtained for the BRZ-PTA and BRZ-TPB membrane electrodes, respectively. The performance of the fabricated membranes was optimum in the pH range of 3–6. Optimum electrochemical response was attained through the careful adjustment of all assay settings. The cited method was successfully applied for the selective determination of BRZ in either its pure form or real wastewater samples obtained from a pharmaceutical industrial plant. The main core of novelty in the suggested method lies in the application of the membranes for the sensitive, selective, and economic determination of BRZ in real wastewater effluents without the tedious sample pretreatment procedures. This can make the suggested method considered an eco-friendly method, as it minimizes the use of organic solvents and chemicals used in the pretreatment process.

Multifunctional dendritic molecular probe for selective detection of Cu2+ ions using potentiometric and fluorometric techniques

We have designed and synthesized a multifunctional dendritic molecular probe that selectively detects Cu2+ ions via potentiometric and fluorometric techniques with low detection limits (3.5 μM in potentiometry, 15 nM in fluorometry). The selective and reversible binding of the molecule with the Cu2+ ion was used to make a solid-state microsensor (diameter of 25 μm) by incorporating the molecular probe into the carbon-based membrane as an ionophore for Cu(II). The Cu(II) microelectrode has a broad linear range of 10 μM to 1 mM with a near Nernstian slope of 30 mV/log [aCu2+] and detection limit of 3.5 μM. The Cu(II) microsensor has a fast response time (1.5 s), and it has a broad working pH range from 3.5 to 6.0. The incorporation of the hydrophobic dendritic moiety makes the ionophore less prone to leaching in an aqueous matrix for potentiometric measurement. The cinnamaldehyde component of the molecule helps detection of Cu2+ ions fluorometrically, as indicated by a change in fluorescence upon selective and reversible binding of the molecular probe to the Cu2+ ions. The strategic design of the molecular probe allows us to detect Cu2+ ions in drinking water by using this novel dendritic fluoroionophore and solid-state Cu2+ - ion-selective microelectrode.

A multi-colorimetric probe to discriminate between heavy metal cations and anions in DMSO-H2O with high selectivity for Cu2+ and CN-: study of logic functions and its application in real samples

A ditopic multi-colorimetric probe based on the phenylpridyl-thioic moiety (EN) was synthesized via a Schiff base reaction mechanism and characterized using ¹H NMR and UV-vis spectroscopy. The colorimetric analyses carried out revealed that EN was capable of discriminating between a number of heavy metal cations via coordination induced charge transfer, as well as between anions through hydrogen bonding induced charge transfer, in DMSO–H₂O (9 : 1). In particular, the ditopic probe could spectrally and colorimetrically recognize the most toxic heavy metal cations of Cd²⁺, Pb²⁺ and Hg²⁺, among others, in DMSO–H₂O. Additionally, EN was selective and sensitive to the presence of CN⁻, F⁻, AcO⁻ and H₂PO₄⁻ in the same solvent system as cations. The reversibility and reproducibility studies showed that EN exhibited complementary IMP/INH logic functions, based on colour and spectral switching (ON/OFF), modulated by F⁻/Al³⁺. The real time application of the probe was tested on food grade products to detect the presence of F⁻ in toothpastes and mouthwash dissolved in water, as well as cations in underground water (normally saline), which displayed substantial responses. Thus, EN displayed an excellent scope of response and can thus be developed for real time sensing kits, which could be used instantly in on-field analysis. Theoretical studies were conducted to complement the experimental work.

A ditopic multi-colorimetric probe based on the phenylpridyl-thioic moiety (EN) was synthesized via a Schiff base reaction mechanism and characterized using ¹H NMR and UV-vis spectroscopy.

Fabrication of Membrane Sensitive Electrodes for the Validated Electrochemical Quantification of Anti-Osteoporotic Drug Residues in Pharmaceutical Industrial Wastewater

Accurate and precise application of ion-selective electrodes (ISEs) in the quantification of environmental pollutants is a strenuous task. In this work, the electrochemical response of alendronate sodium trihydrate (ALN) was evaluated by the fabrication of two sensitive and delicate membrane electrodes, viz. polyvinyl chloride (PVC) and glassy carbon (GC) electrodes. A linear response was obtained at concentrations from 1 × 10-5 to 1 × 10-2 M for both electrodes. A Nernstian slope of 29 mV/decade over a pH range of 8-11 for the PVC and GC membrane electrodes was obtained. All assay settings were carefully adjusted to obtain the best electrochemical response. The proposed technique was effectively applied for the quantification of ALN in pure form and wastewater samples, acquired from manufacturing industries. The proposed electrodes were effectively used for the determination of ALN in real wastewater samples without any prior treatment. The current findings guarantee the applicability of the fabricated ISEs for the environmental monitoring of ALN.

Trace level monitoring of Cu(II) ion using CuS particles based membrane electrochemical sensor

Cu(II) monitoring is a matter of great interest to researchers due to its toxicity and adverse environmental effects. Among different methods for detecting Cu(II), ion-selective electrode (ISE) is more advantageous as they are low-cost, easy to fabricate, and highly selective. Here, we report a simple, inexpensive, and reproducible procedure for the fabrication of Cu(II) ion-selective electrodes using CuS particles and polyvinyl chloride (PVC) as a matrix. CuS particles, obtained by chemical precipitation, were characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), and energy-dispersive X-Ray spectroscopy (EDX). Optimization of the membrane compositions was done to get a well-behaved sensor by varying amounts of CuS, PVC, and acetophenone (AP). A membrane composition of 0.4 g CuS, 0.5 g PVC, and 1.0 mL AP in 5.0 mL tetrahydrofuran (THF) gave a Nernstian slope of 27.31 mV per decade change of Cu(II) ion over a wide range of concentration down to 64 ppb (1 × 10⁻⁶ M). The sensor gave a fast response time of 25 s, and it indicated the endpoint in a potentiometric titration of Cu(II) with standard EDTA solution. A pH-independent potential response was obtained in the pH 4.0–6.0.

High Sensitive Sensor Fabricated by Reduced Graphene Oxide/Polyvinyl Butyral Nanofibers for Detecting Cu (II) in Water

Graphene oxide (GO)/polyvinyl butyral (PVB) nanofibers were prepared by a simple electrospinning technique with PVB as matrix and GO as a functional nanomaterial. GO/PVB nanofibers on glassy carbon electrode (GCE) were reduced through electrochemical method to form reduced graphene oxide (RGO)/PVB nanofibers. The morphology and structure of GO/PVB nanofiber were studied by scanning election microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR). RGO/PVB modified GCE was used for fabricating an electrochemical sensor for detecting Cu (II) in water. The analysis results showed that RGO/PVB modified GCE had good analytical results with the linear range of 0.06–2.2 μM, detection limit of 4.10 nM (S/N = 3), and the sensitivity of 103.51 μA·μM⁻¹·cm⁻².

A colorimetric and luminescent dual-modal assay for Cu(II) ion detection using an iridium(III) complex

A novel iridium(III) complex-based chemosensor bearing the 5,6-bis(salicylideneimino)-1,10-phenanthroline ligand receptor was developed, which exhibited a highly sensitive and selective color change from colorless to yellow and a visible turn-off luminescence response upon the addition of Cu(II) ions. The interactions of this iridium(III) complex with Cu2+ ions and thirteen other cations have been investigated by UV-Vis absorption titration, emission titration, and 1H NMR titration.

In vitro interceptive and reparative effects of myo-inositol against copper-induced oxidative damage and antioxidant system disturbance in primary cultured fish enterocytes

Copper (Cu) is essential for normal cellular processes in most eukaryotic organisms but is toxic in excess. Our previous study reported that a nutrient antioxidant, myo-inositol (MI), can protect fish from Cu-induced oxidative injury; however, the mechanisms involved are not fully understood. Therefore, the present study aimed to analyze potential pathways. First, to investigate the hypothesis that MI protects enterocytes against Cu toxicity via the intercept pathway, enterocytes were treated with different concentrations of MI (0-75mg/L medium) in the presence of 6mg/L of Cu for 24h (Experiment 1). Next, we investigated the potential reparative role of MI after a Cu challenge (Experiment 2). The results of Experiment 1 indicated that cells exposed to Cu alone for 24h exhibited increases in lactate dehydrogenase release (LDH), malondialdehyde (MDA) formation and protein oxidation (P<0.05). Notably, a dose-dependent inhibitory effect on LDH release was observed with all doses of MI. Moreover, co-treatment with MI completely inhibited Cu-induced protein carbonyl (PC) formation. However, Cu-induced lipid peroxidation was not altered by MI co-treatment. Additionally, Cu exposure suppressed total-superoxide dismutase (T-SOD), CuZnSOD and catalase (CAT) activities, and these changes were completely blocked by co-treatment with sufficient MI concentrations. In contrast, cells exposed to Cu exhibited adaptive increases in reduced glutathione (GSH) content and the activities of anti-hydroxyl radical (AHR), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reductase (GR). Interestingly, the Cu-stimulated increases in these antioxidants were blocked by co-treatment with sufficient MI concentrations. The results of Experiment 2 indicated that cell injury (LDH release), lipid peroxidation (MDA formation) and protein oxidation induced by Cu were reversed by subsequent MI treatment. Meanwhile, Cu-induced decreases in alkaline phosphatase (AKP), anti-superoxide anion (ASA), T-SOD and CuZnSOD activities were completely restored by subsequent MI treatment, while the reduced CAT activity was partially restored. However, MI rescues partially restored the adaptive increase in GPx activity induced by Cu, whereas the adaptive increase in reduced GSH content was completely reversed by 75mg/L of MI. However, subsequent MI treatments did not alter the induction of GST activity by Cu. In conclusion, we demonstrated for the first time that MI not only protected enterocytes from Cu-induced oxidative damage but also increased the repair activity in primary enterocytes after challenge with Cu. Moreover, MI-mediated increases in antioxidant enzyme activities contributed to lipid and protein oxidant repair.

A ferrocene-porphyrin ligand for multi-transduction chemical sensor development

5,10,15,20-Tetraferrocenyl porphyrin, H2TFcP, a simple example of a donor-acceptor system, was tested as ligand for the development of a novel multi-transduction chemical sensors aimed at the determination of transition metal ions. The fluorescence energy transfer between ferrocene donor and porphyrin acceptor sub-units was considered. The simultaneously measured optical and potentiometric responses of solvent polymeric membranes based on H2TFcP permitted the detection of lead ions in sample solutions, in the concentration range from 2.7 × 10(-7) to 3.0 × 10(-3) M. The detection limit of lead determination was 0.27 μM, low enough to perform the direct analysis of Pb2+ in natural waters.

Colorimetric detection of copper ions based on a supramolecular complex of water-soluble polythiophene and ATP

A colorimetric probe for the detection of copper(II) ions in aqueous media by the naked eye has been developed based on a supramolecular complex comprised of a cationic polythiophene derivative and ATP with a detection limit as low as 0.05 mM.

Terbium hybrid particles with spherical shape as luminescent probe for detection of Cu2+ and Fe3+ in water

A novel green emissive terbium inorganic-polymeric hybrid particle was designed and this material could detect cations in water. Polyvinyl alcohol as an amphiphilic surfactant rendered the powders dispersible in water with regular round shape (10-20 μm). Interestingly, we noticed that not only Cu(2+) (detection limit 10(-4)M) but also Fe(3+) (detection limit 10(-4) M) can give rise to emission quenching to this target material in comparison with K(+), Na(+), Fe(2+), Mn(2+), Pd(2+), Cd(2+) and Co(2+) (10(-3) mol L(-1)). We regarded that the coordination interactions between ligand and metal ions resulted in these quenching processes. Additionally, it was found that the sensing material can be repeatedly used at least 5 cycles. More importantly, this novel material demonstrated higher thermal-stability in aqueous media than pure silica hybrid material.

Electrochemical Analysis of Some Toxic Metals by Ion-Selective Electrodes

An overview of potentiometric sensors that are capable of detecting toxic heavy metal ions in environmental samples is presented and discussed. Notwithstanding the tremendous work performed so far, it is obvious that still several limitations do exist in terms of selectivity, limits of detection, dynamic ranges, applicability to specific problems, and reversibility. A survey on important advances in potentiometric sensors with regard to high selectivity, lower detection limit, fast response time, and on-line environmental analysis is presented in this review article. [Supplemental materials are available for this article. Go to the publisher's online edition of Critical Reviews in Analytical Chemistry to view the free supplemental file.].

Development of membrane electrodes for selective determination of some antiepileptic drugs in pharmaceuticals, plasma and urine

Newly developed, simple, low-cost and sensitive ion-selective electrodes have been proposed for determination of some antiepileptic drugs such as lamotrigine, felbamate, and primidone in their pharmaceutical preparations as well as in biological fluids. The electrodes are based on poly(vinyl chloride) membranes doped with drug-tetraphenyl borate (TPB) or drug-phosphotungstic acid (PT) ion-pair complexes as molecular recognition materials. The novel electrodes displayed rapid Nernstian responses with detection limits of approximately 10(-7) M. Calibration graphs were linear over the ranges 5.2 x 10(-7)-1.0 x 10(-3), 1.5 x 10(-6)-1.0 x 10(-3), and 2.6 x 10(-7)-1.0 x 10(-3 )M for drug-TPB and 5.8 x 10(-7)-1.0 x 10(-3), 1.8 x 10(-7)-1.0 x 10(-3), and 6.6 x 10(-7)-1.0 x 10(-3) M for drug-PT electrodes, respectively, with slopes ranging from 52.3 to 62.3 mV/decade. The membranes developed have potential stability for up to 1 month and proved to be highly selective for the drugs investigated over other ions and excipients. The results show that the selectivity of the ion-selective electrodes is influenced significantly by the plasticizer. The proposed electrodes were successfully applied in the determination of these drugs in pharmaceutical preparations in four batches of different expiry dates. Statistical Student's t test and F test showed insignificant systematic error between the ion-selective electrode methods developed and a standard method. Comparison of the results obtained using the proposed electrodes with those found using a reference method showed that the ion-selective electrode technique is sensitive, reliable, and can be used with very good accuracy and high percentage recovery without pretreatment procedures of the samples to minimize interfering matrix effects.

8-hydroxyquinoline based neutral tripodal ionophore as a copper (II) selective electrode and the effect of remote substitutents on electrode properties

New PVC membrane ion selective electrodes based on 1,3,5-Tris(8-quinolinoxymethyl)-2,4,6-trimethylbenzene (MO8HQ) are reported. The basic sensing material belongs to the group of tripodal ionophores. Also their derivatives prepared by placing suitable substitutents at fifth position of 8-oxine moiety, i.e, 1,3,5-Tris(5-chloro-8-quinolinoxymethyl)-2,4,6-trimethylbenzene (5CHQ), 1,3,5-Tris(5-benzoyl-8-quinolinoxymethyl)-2,4,6-trimethylbenzene (5BHQ) and 1,3,5-Tris[(5-phenylhydroxymethylene)-8-quinolinoxymethyl]-2,4,6-trimethylbenzene (HYD-8HQ) ionophores have also been used to make copper-selective membrane electrodes. Among all the four electrodes, MO8HQ and HYD-8HQ ionophores based electrodes show excellent response towards Cu (II) ions. The electrodes having composition 33% PVC, 4% MO8HQ and 63% dibutyl phthalate (DBP) and 33% PVC, 6% HYD-8HQ, 63% dibutyl phthalate (DBP) exhibit a good Nernstian response to Cu (II) ions in the range of 1.0 x 10(-6) to 1 x 10(-1) M. The electrode shows a reasonably fast response time of 15 s. The effect of pH and electrode response is also reported. It shows good selectivity for Cu (II) ions in comparison to heavy metal ions, transition metal ions and for alkali and alkaline earth metal ions. The electrode response and selectivity remains unchanged for at least 5 months. The electrode can be used as an indicator electrode in the potentiometric titration of Cu (II) ions with EDTA.