Highly Selective and Sensitive Copper(II) Membrane Sensors Based on 6‐Methyl‐4‐(1‐phenylmethylidene)amino‐3‐thioxo‐1,2,4‐triazin‐5‐one as a New Neutral Ionophore

A new Cu(II) ion‐selective PVC membrane sensor based on 6‐methyl‐4‐(1‐phenylmethylidene)amino‐3‐thioxo‐1,2,4‐triazin‐5‐one (MATTO) as an excellent sensing material was developed. The electrode exhibits a Nernstian slope of 29.2±0.4 mV per decade over a very wide concentration range between 1.0×10^?1 and 1.0×10^?6 M, with a detection limit of 4.8×10^?7 M (30.5 ng/mL). The sensor possesses the advantages of short conditioning time, fast response time (<10 s), and especially, very good selectivity towards transition and heavy metal, and some mono, di and trivalent cations. The proposed electrode was successfully applied to the determination of copper in wastewater of copper electroplating samples and as an indicator electrode in potentiometric titration of Cu(II) ions with EDTA.     

A Novel PVC‐Membrane‐Coated Graphite Sensor Based on an Anthraquinone Derivative Membrane for the Determination of Lead

A highly selective membrane electrode for the determination of ultratrace amounts of lead was prepared. The PVC membrane electrode based on 2‐(2‐ethanoloxymethyl)‐1‐hydroxy‐9,10‐anthraquinone (AQ), directly coated on graphite, exhibits a good Nernstian response for Pb(II) ions over a very wide concentration range (1.0×10^?7–1.0×10^?2 M) with a limit of detection of 8.0×10^?8 M. It has a fast response time of ca. 10 s and can be used over a period 2 months with good reproducibility (SD=±0.2 mV). The electrode revealed a very good selectivity respect to common alkali, alkaline earth, transition and heavy metal ions and could be used in the pH range of 3.5–6.8. It was used as an indicator electrode in potentiometric titration of lead ions with chromate and oxalate, and in indirect determination of lead in spring water samples.     

Erbium(III) PVC Membrane Ion-Selective Sensor based on 4-(2-Thiazolylazo)resorcinal

Abstract

4-(2-Thiazolylazo)resorcinol (TR) was used as a new compound to play the role of an excellent ion carrier in the fabrication of an Er(III) membrane electrode. The electrode shows a very good selectivity toward Er(III) ions over a wide variety of cations, including alkali, alkaline earth, transition, and heavy-metal ions. The proposed sensor exhibits a Nernstian behavior (with slope of 19.6 ± 0.6 mV per decade) over a wide concentration range (1.0 × 10^?6 to 1.0 × 10^?2 M). The detection limit of the sensor is 6.6 × 10^?7 M. It has a very short response time, in the whole concentration range (～10 s), and can be used for at least 12 weeks in the pH range of 2.8–9.3. The proposed sensor was successfully applied as an indicator electrode for the potentiometric titration of a Er(III) solution, with EDTA. It was also successfully applied to the F^? ion determination in some mouthwashing solutions.     

Triiodide PVC Membrane Electrode Based on a Charge‐Transfer Complex of Iodine with Ditertbutyl‐Dicyclohexyl‐18‐Crown‐6

A new triiodide ion‐selective electrode based on a charge‐transfer complex of iodine with ditertbutyl‐dicyclohexyl‐18‐crown‐6 (t‐Bu)₂DC18C6 as membrane carrier was prepared. The electrode has a linear dynamic range from 6.3 × 10^?3‐5 × 10^?6 with a Nernstian response of 58.6 ± 1 mV decade^?1 and a detection limit of 1.3 × 10^?6 M. The response time of the sensor was 25 s. The membrane could be used for two months without any divergence in potentials. The electrode exhibits an anti‐Hofmeistetr selectivity sequence with a preference for triiodide at pH 2.0‐10.0. The response mechanism of the electrode was investigated by Uv‐Vis spectroscopic technique. The electrode can be used for the determination of ascorbic acid in orange juice.     

Determination of Hg(II) ions in water samples by a novel Hg(II) sensor,based on calix[4]arene derivative

A PVC membrane electrode for Hg(II) ions, based on a new cone shaped calix[4]arene (L) as a suitable ionophore was constructed. The sensor exhibits a linear dynamic in the range of 1.0 × 10^?6–1.0 × 10^?1 M, with a Nernstian slope of 29.4 ± 0.4 mV decade^?1, and a detection limit of 4.0 × 10^?7 M. The response time is quick (less than 10 s), it can be used in the pH range of 1.5–4, and the electrode response and selectivity remained almost unchanged for about 2 months. The sensor revealed comparatively good selectivity with respect to most alkali, alkaline earth, and some transition and heavy metal ions. It was successfully employed as an indicator electrode in the potentiometric titration of Hg²⁺ ions with potassium iodide, and the direct determination of mercury content of amalgam alloy and water samples.     

Voltammetric Determination of Uric Acid with a Glassy Carbon Electrode Coated by Paste of Multiwalled Carbon Nanotubes and Ionic Liquid

The voltammetric behavior of uric acid (UA) has been studied at a multiwalled carbon nanotube‐ionic liquid (i.e., 1‐butyl‐3‐methylimidazolium hexafluorophosphate, BMIMPF₆) paste coated glassy carbon electrode (MWNTs‐BMIMPF₆/GC). It is found that UA can effectively accumulate at this electrode and cause a sensitive anodic peak at about 0.49 V (vs. SCE) in pH 4.0 phosphate buffer solutions. Experimental parameters influencing the response of the electrode, such as solution pH and accumulation time, are optimized for uric acid determination. Under the optimum conditions, the anodic peak current is linear to UA concentration in the range of 1.0×10^?8 M to 1.0×10^?6 M and 2.0×10^?6 M to 2.0×10^?5 M. The detection limit is 5.0×10^?9 M for 180 s accumulation on open circuit. The electrode can be regenerated by successively cycling in a blank solution for about 3 min and exhibits good reproducibility. A 1.0×10^?6 M UA solution is measured for eight times using the same electrode regenerated after every determination, and the relative standard deviation (RSD) of the peak current is 3.2%. As for different electrodes fabricated by the same way the RSD (i.e., the electrode to electrode deviation) is 4.2%(n=9). This method has been applied to the determination of UA in human urine samples, and the recoveries are 99%–100.6%. In addition, comparison is made between MWNTs‐BMIMPF₆/GC and MWNTs/GC. Results show that the MWNTs‐BMIMPF₆/GC exhibits higher sensitivity, selectivity and ratio of peak current to background current.     

Potentiometric Determination of Sibutramine Using Batch and Flow Injection Analysis

Sibutramine (SBT⁺) ion-selective electrode (ISE) was constructed using poly(vinyl chloride) matrix membrane containing sibutramine–phosphotungstate (SBT–PTA) plasticized with dioctyl phthalate. The electrode exhibits Nernstian response of 59.54 mV/ concentration decade over the concentration range 1.0 × 10^?5 to 1.0 × 10^?2 M and detection limit of 7.94 × 10^?6 M. The electrode was fully characterized in terms of its composition, response time, life span, pH, selectivity, and temperature and was then applied to the potentiometric determination of SBT in its pure bulk and pharmaceutical formulations under batch and flow injection conditions and for the in vitro testing of the dissolution profile of SBT capsules.     

Lead-selective electrode based on the misfit compound (PbS)1.18TiS2

A lead-selective solid-contact electrode was prepared on the basis of the misfit compound (PbS)_1.18TiS₂. The electrode exhibits the slope of the electrode function is -(26 ±1) mV/pc and provides the determination of 1 × 10^-5-5 × 10^-2 M lead in the pH range 2.75–5.0. High selectivity of the electrode for Ni²⁺, Co²⁺, Zn²⁺, Cu²⁺, Ag⁺, K⁺, Ba²⁺, and Sr²⁺ ions was demonstrated. The addition of graphite to the active phase of the membrane impaired the selectivity of the electrode. The electrode was used for the potentiometric indication of the titration end point in the determination of lead in copper alloys. Presented at the V All-Russian Conference with the Participation of CIS Countries on Electrochemical Methods of Analysis (EMA-99), Moscow, December 6–8, 1999.     

Simultaneous Determination of Dopamine and Ascorbic Acid at an In‐Site Functionalized Self‐Assembled Monolayer on Gold Electrode

The in‐site functionalization of 4‐aminothiophenol (4‐ATP) self‐assembled monolayer on gold electrode at physiological pH yields a redox active monolayer of 4′‐mercapto‐N‐phenylquinone diimine (MNPD). The functionalized electrode exhibits excellent electrocatalytic responses towards dopamine (DA) and ascorbic acid (AA), reducing the overpotentials by about 0.22 V and 0.34 V, respectively, with greatly enhanced current responses. Due to its different catalytic activities toward DA and AA, the modified electrode resolves the overlapping voltammetric responses of DA and AA into two well‐defined voltammetric peaks by differential pulse voltammetry (DPV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak current obtained from DPV was linearly related to DA and AA concentration in the ranges of 5.0×10^?6?1.25×10^?4 M and 8.0×10^?6?1.3×10^?4 M with correlation coefficient of 0.999 and 0.998, respectively. The detective limits (3σ) for DA and AA were found to be 1.2×10^?6 M and 2.4×10^?6 M, respectively. The modified electrode shows good sensitivity, selectivity and stability, and has been applied to the determination of DA and AA simultaneously in samples with satisfactory results.     

Subnanomolar determination of a beryllium ion by a novel Be(II) microsensor based on 4-nitrobenzo-9-crown-3-ether

In this work, for the first time, we introduce a highly selective and sensitive Be(II) microsensor. 4-nitrobenzo-9-crown-3-ether (NBCE) was used as a membrane-active component to prepare a Be(II)-selective polymeric membrane microelectrode. The electrode exhibits a Nernstian response toward Be(II) ions over a very wide concentration range (1.0 × 10⁻⁴–1.0 × 10⁻¹⁰ M), with a detection limit of 3.5 × 10⁻¹¹ M (∼350 pg/L). In fact, the electrode presents a fast response time in the whole concentration range (6 s). The proposed microelectrode can be used for at least six weeks without any considerable divergence in the potentials. The proposed membrane sensor revealed a selectivity toward Be(II) ions over a wide variety of other metal ions including common alkali, alkaline-earth, and rare-earth ions. It could be used in the pH range of 3.0–11.5. The microelectrode was successfully used as an indicator electrode for the titration of 20 mL of 1.0 × 10⁻⁶ M Be²⁺ solution with 1.0 × 10⁻⁴ M of EDTA. It was also applied to the direct determination of beryllium ions in beryl and binary mixtures. The text was submitted by the authors in English.     

Highly Selective and Sensitive Tin(II) Membrane Electrode Based on a New Synthesized Schiff's Base

Studies on complex formation of tris(3‐(2‐hydroxybenzophenone)propyl)amine (THPA) with a number of metal ions in acetonitrile solution revealed the occurrence of a selective 1 : 1 complexation of the proposed ligand with Sn²⁺ ion. Consequently, THPA was used as a suitable neutral ionophore for the preparation of a polymeric membrane‐selective electrode. The electrode exhibits a Nernstian behavior with a slope of 29.4±0.3 mV per decade and a detection limit of 2.0×10^?7 M. It also showed a good selectivity for Sn²⁺ ions in comparison with some of group A and B metal ions over a wide concentration range of 5.0×10^?7–1.0×10^?1 M. Improved selectivity was achieved compared to the best selectivity recently reported by other authors for tin(II). The electrode was successfully applied to the determination of Sn²⁺ ion in waste water and various canned products.     

Terbium(III) Ion-Selective Electrochemical Sensor Based on Hematoporphyrin

Abstract

A polyvinyl chloride (PVC) based membrane sensor for terbium ions was prepared by employing Hematoporphyrin (HP) as an ionophore. The sensor revealed a very good selectivity (expect for the Fe³⁺ion) with respect to common alkali, alkaline earth and heavy metal ions. The plasticized membrane electrode exhibits a Nernstian response for Tb³⁺ ions over a wide concentration range (1.0 × 10^?6 ? 1.0 × 10^?2 M) with a slope of 19.8±0.3 mV per decade and low detection limit of 7.4 × 10^?7 M. The developed sensor was used in determination of F^? in mouth wash preparation sample.     

Electro‐oxidation and Determination of Tripelennamine Hydrochloride at MWCNT‐CTAB Modified Glassy Carbon Electrode

An electrochemical method for the determination of tripelennamine hydrochloride (TPA) using cetyltrimethylammoniumbromide‐multiwalled carbon nanotubes modified glassy carbon electrode (MWCNT‐CTAB/GCE) was developed. Because of good electrical conductivity of MWCNT and catalytic behavior of CTAB, new electrode significantly enhances the sensitivity for the detection of TPA. Parameters such as amount of modifier suspension, scan rate, pH of measure solution, heterogeneous rate constant were investigated. The electrode exhibits a linear potential response in the range of 1.0×10^?8 M to 3.0×10^?6 M with a detection limit of 2.38× 10^?9 M. The modified electrode was successfully applied to the determination of TPA in pharmaceutical and real samples.     

Ion Selective Electrode for Potentiometric Determination of Saccharin Using a Thin Film of Silsesquioxane 3-n-Propylpyridinium Chloride Polymer Coated-Graphite Rod

ABSTRACT

A polymer coated graphite rod ion selective electrode for saccharin was constructed and evaluated for the determination of saccharin in artificial table top sweeteners. The polymer consists of a thin film of silsesquioxane 3-n-propylpyridinium chloride. The electrode response was based on the ion pair formed between saccharinate and the 3-n-propylpyridinium cation from the silsequioxane polymer. The electrode exhibits a Nernstian response for saccharin concentrations between 6.9×10^-6 and 5.3×10^-3 mol L^-1 and a detection limit of 5.5×10^-6 mol L^-1. The electrode response for saccharin was fast (10-20 s) and the potential independent of pH in the range of 3 to 7. The selectivity coefficients K _{A, B} ^pot for several anions usually present in commercial table top sweeteners were determined following the IUPAC recommendations. The potentiometric method with the ion selective electrode was validated by the HPLC reference method, through t8543226 determination of saccharin in commercial samples of table top sweeteners. The ion selective electrode is proved suitable for the routine quality control of table top sweeteners by potentiometry.     

A Novel Al(III)‐Selective Electrochemical Sensor Based on N,N′‐Bis(salicylidene)‐1,2‐phenylenediamine Complexes

A polyvinylchloride membrane sensor based on N,N′‐bis(salecylidene)‐1,2‐phenylenediamine (salophen) as membrane carrier was prepared and investigated as a Al³⁺‐selective electrode. The sensor exhibits a Nernstian response toward Al(III) over a wide concentration range (8.0×10^?7–3.0×10^?2 M), with a detection limit of 6.0×10^?7 M. The potentiometric response of the sensor is independent of the pH of the test solution in the pH range 3.2–4.5. The electrode possesses advantages of very fast response and high selectivity for Al³⁺ in comparison with alkali, alkaline earth and some heavy metal ions. The sensor was used as an indicator electrode, in the potentiometric titration of aluminum ion and in determination of Al³⁺ contents in drug, water and waste water samples.     

Be(II) Graphite Coated Membrane Sensor Based on a Recently Synthesized Benzo‐9‐Crown‐3 Derivative

A highly sensitive and selective membrane electrode with 9‐crown‐3 derivative (CD) as ionophore, potassium tetrakis‐(p‐chlorophenyl) borate as anionic additive (KTB), acetophenone (AP) as solvent mediator was prepared and investigated as a Be(II) sensor. The best performance was observed with the membrane having the percent ratio 30% PVC: 8% CD: 6% KTB: 56% Acetophenone. The poly(vinyl chloride) PVC membrane containing 9‐crown‐3 derivative (CD) directly coated on a graphite electrode, shows a Nernstian response for Be(II) ions over a very wide concentration range (1.0×10^?1?1.0×10^?7 M) with a detection limit of 8.0×10^?8 M (ca. 0.72 ng/mL). It has a fast response time of ca. 20 s and can be used for at least 10 weeks without any major deviation in potential. The proposed sensor exhibits very good selectivity with respect to common alkali, alkaline earth, transition and heavy metal ions. The proposed sensor was used as end point indicator electrode in the titration of Be(II) ions with EDTA. It was also applied to determination of Be(II) in real sample.     

Determination of cerium(III) ions in soil and sediment samples by Ce(III) PVC-based membrane electrode based on 2,5-dioxo-4-imidazolidinyl

2,5-Dioxo-4-imidazolidinyl was used as an excellent sensing material in the preparation of a PVC membrane for a Ce(III)-selective sensor. The electrode shows a good selectivity for the Ce(III) ion with respect to most common cations including alkali, alkaline earth, transition, and heavy metal ions. The developed sensor exhibits a wide linear response with a slope of 19.6?±?0.3 mV per decade over the concentration range of 1.0?×?10^?6 to 1.0?×?10^?1 M, while the illustrated detection limit is 5.7?×?10^?7 M of Ce(III) ions. Moreover, it is concluded that the sensor response is pH-independent in the range of 3.1–9.8. The applications of the recommended electrode include the determination of concentration of Ce(III) ions in soil and sediment samples, validation with CRM's, and the Ce(III) ion potentiometric titration with EDTA as an indicator electrode.     

Anodic stripping voltammetric determination of silver(I) in water using a 4-tert-butyl-1(ethoxycarbonylmethoxy)thiacalix[4]arene modified glassy carbon electrode

A glassy carbon electrode coated with film of 4-tert-butyl-1-(ethoxycarbonylmethoxy)thiacalix[4]arene is designed for the determination of trace amounts of Ag⁺. Compared with bare glassy carbon electrode, the modified electrode can greatly improve the measuring sensitivity for Ag⁺. Under the optimum experimental conditions, the modified electrode in B-R buffer solution (pH 4.5) shows a linear voltammetric response in the range of 5.0 × 10⁻⁸–3.0 × 10⁻⁶ M with detection limit 1.0 × 10⁻⁸ M for Ag⁺. The high sensitivity, selectivity, and stability of modified electrode also demonstrate its practical application for a simple, rapid and economical determination of Ag⁺ in water samples.     

Mercury selective membrane electrode based on dithio derivatized macrotricyclic compound

A novel dithio derivatized macrotricyclic compound (cryptand) has been synthesized using high dilution technique by condensation of diaminodibenzo18-crown-6 with 2, 2′dithiobenzoyl chloride. The compound was characterized by elemental analysis, ¹H NMR, ¹³C NMR and FAB-MS. PVC membrane electrode based on this macrotricyclic compound showed good selectivity for Hg²⁺ ion with a wide linear range of 1.0 × 10^?6 to 1.0 × 10^?1 M and a lower detection limit of 5.0 × 10^?6 M with a calibration slope of 30.2 mV decade^?1. The electrode response was stable in pH range 3–6. Electrode showed good selectivity for Hg²⁺ over other interfering metal ions. The electrode was then applied to direct determination of Hg²⁺ in water samples.     

Determination of copper(II) in wastewater by electroplating samples using a PVC-membrane copper(II)-selective electrode

A PVC membrane containing 4-amino-6-methyl-1,2,4-triazin-3,5-dithione (AMTD) as a suitable ionophore, exhibits a Nernstian response for Cu²⁺ ions over a wide concentration range up to 1 × 10⁻¹ and 1 × 10⁻⁶ M, with a detection limit of 7.5 × 10⁻⁷ M in the pH range 3.0–7.5. It has a fast response time (<15 s) and can be used for at least 12 weeks without any major deviation in the potential. The electrode revealed a very good selectivity with respect to all common alkali, alkaline-earth, transition, and heavy-metal ions. It was successfully applied to the recovery of copper ions from wastewater. The electrode was also used as an indicator electrode in the potentiometric titration of Cu(II) ions with EDTA. The text was submitted by the authors in English.