Potentiometric sensors based on organic ion exchangers for determining tetraalkylammonium salts

Potentiometric sensors with plasticized polymer membranes based on organic ion exchangers, tetraalkylammonium dodecyl sulfates (benzyldimethyldodecylammonium, benzyldimethyltetradecylammonium, dimethyldistearylammonium), have been proposed for the determination of quaternary ammonium salts in model solutions and KATAPAV technical solutions. The thermal stability, composition, and solubility product have been estimated. It has been shown that ion associates are stable to 60?C70°C, K _S varies in the range from 2 × 10^?8 to 5 × 10^?10. The basic electrochemical parameters of the sensors have been determined as well, such as linearity ranges of the electrode function (5 × 10^?5 (5 × 10^?6)?1 × 10^?2 (1 × 10^?3) M) and slopes of the electrode functions (47?C59 mV/pc), response time (60?C90 sec), potential drift (2?C3 mV/day), operation period (3?C4 months), limits of detection for tetramethylammonium salts (1 × 10^?5?4 × 10^?7 M).     

Development of Polymeric Resin Ion‐exchanger Based Chloride Ion‐selective Electrode for Monitoring Chloride Ion in Environmental Water

A chloride ion‐selective electrode (ISE) membrane was developed by using a copolymeric ion‐exchanger resin (trimethyl ethenyl quaternary ammonium chloride polystyrene‐divinylbenzene copolymer resin, TMEQAC PSDVB), the ionophore ({μ‐[4,5‐Dimethyl‐3,6‐bis(dodecyloxy)‐1,2‐phenylene]}bis(mercury chloride), ETH9033), the plasticizer (bis(2‐ethylhexyl) sebacate, DOS), and the membrane substrate (polyvinylchloride, PVC). At 25 °C, the electrode exhibited an ideal Nernstian response of 59.2 mV/decade with the linear calibration concentration range from 1.0 × 10^?4‐1.0 × 10^?2 M (r² = 0.9930). The limit of detection was 2.45 ppm (6.9 × 10^?2 mM) and the measurement response time was less than 10 seconds. The working temperature range of electrode was 10‐45 °C. The working pH range for chloride ion measurement was 2.0‐11.0. Among the various anions examined in this work, only I^?, SCN^?, and MnO₄^? ions show significant interference to the electrode measurement. The chloride ISE can be used at least 72 days. The determination of chloride ion content in three kinds of environmental water sample with the electrode method was accurate (92‐95%) and precise (RSD < 4.4%) and did not show significance difference from the high‐performance liquid chromatography method.     

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.     

Cobalt(II)-selective membrane electrode based on N,N′-di(thiazol-2-yl)formimidamide

A new PVC-membrane electrode for Co²⁺ ions based on N,N′-di(thiazol-2-yl)formimidamide (TF) as membrane carrier has been developed. The electrode resulted in Nernstian response (29.5?±?0.4?mV decade^?1) for Co²⁺ ion over a wide concentration range (2.5?×?10^?7 ?1.0?×?10^?1?M) with a detection limit of 6.1?×?10^?8?M. The sensor has a response time of about 10?s, and can be used for at least 2 months without observing any deviation from the Nernstain response. The electrode revealed good selectivity towards cobalt(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in the pH range 2.0–7.0. The electrode was used for determination of Co²⁺ in real samples.     

Sensitive determination of ATP using a carbon paste electrode modified with a carboxyl functionalized ionic liquid

We report on a new electrode for the determination of adenosine-5??-triphosphate (ATP). It is based on modified carbon paste electrode that contains an ionic liquid (IL) as the binder. The electrode shows strong electrocatalytic oxidative activity towards ATP at pH 4.5 in giving a well-defined single oxidation peak. The oxidation reaction is adsorption-controlled and due to the presence of the highly conductive IL. The electron transfer rate constant was calculated to be 2.04×10^?C3 s^?C1, and the surface coverage is 1.11×10^?C10 mol cm^?C2. Under the selected conditions, the oxidation peak current changes linearly with the concentration of ATP in the range from 5.0 to 1000???mol L^?1 and a detection limit of 1.67???mol L^?1 (3???) as determined by differential pulse voltammetry. The method displays good selectivity and was applied to the determination of ATP injection samples with satisfactory results.

Synergetic effect of Prussian blue film with gold nanoparticle graphite–wax composite electrode for the enzyme-free ultrasensitive hydrogen peroxide sensor

Enzyme-free amperometric ultrasensitive determination of hydrogen peroxide (H₂O₂) was investigated using a Prussian blue (PB) film-modified gold nanoparticles (AuNPs) graphite–wax composite electrode. A stable PB film was obtained on graphite surface through 2-aminoethanethiol (AET)-capped AuNPs by a simple approach. Field emission scanning electron microscope studies results in formation of PB nanoparticle in the size range of 60–80 nm. Surface modification of PB film on AET–AuNPs–GW composite electrode was confirmed by Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy studies. Highly sensitive determination of H₂O₂ at a peak potential of ?0.10 V (vs. SCE) in 0.1 M KCl PBS, pH?=?7.0) at a scan rate of 20 mVs^?1 with a sensitivity of 23.58 μA/mM was observed with the modified electrode using cyclic voltammetry. The synergetic effect of PB film with AuNPs has resulted in a linear range of 0.05 to 7,800 μM with a detection limit of 0.015 μM for H₂O₂ detection with the present electrode. Chronoamperometric studies recorded for the successive additions of H₂O₂ with the modified electrode showed an excellent linearity (R ²?=?0.9932) in the range of 4.8?×?10^?8 to 7.4?×?10^?8 M with a limit of detection of 1.4?×?10^?8 M. Selective determination of H₂O₂ in presence of various interferents was successfully demonstrated. Human urine samples and stain remover solutions were also investigated for H₂O₂ content.     

Acetylferrocene Modified Carbon Paste Electrode; A Sensor for Electrocatalytic Determination of Hydrazine

The electrocatalytic oxidation of hydrazine at a carbon paste electrode spiked with acetylferrocene as a mediator was studied by cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. In contrast to other ferrocenic compounds, acetylferrocene exhibits a chemical irreversible behavior, but it can act as an effective mediator for electrocatalytic oxidation of hydrazine, too. The heterogeneous electron transfer rate constant between acetylferrocene and the electrode substrate (carbon paste) and the diffusion coefficient of spiked acetylferrocene in silicon oil were estimated to be about 3.45×10^?4 cm s^?1 and 4.45×10^?9 cm² s^?1, respectively. It has been found that under the optimum conditions (pH 7.5) the oxidation of hydrazine occurs at a potential of about 228 mV less positive than that of an unmodified carbon paste electrode. The catalytic oxidation peak current of hydrazine was linearly dependent on its concentration and the obtained linear range was 3.09×10^?5 M–1.03×10^?3 M. The detection limit (2σ) has been determined as 2.7×10^?5 M by cyclic voltammetry. Also, the peak current was increased linearly with the concentration of hydrazine in the range of 1×10^?5 M–1×10^?3 M by differential pulse voltammetry with a detection limit of 1×10^?5 M. This catalytic oxidation of hydrazine has been applied as a selective, simple, and precise new method for the determination of hydrazine in water samples.     

Electroanalysis of Dopamine at RuO2 Modified Vertically Aligned Carbon Nanotube Electrode

Electrochemical behavior of dopamine at the RuO₂‐modified vertically aligned carbon nanotubes electrode was investigated by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The RuO₂‐modified carbon nanotube electrode showed higher electrocatalytic activity towards the oxidation of dopamine than the MWNTs electrode in 0.10 M phosphate buffer solution. At an applied potential of +0.4 V, the RuO₂/MWNTs electrode exhibited a wide detection range up to 3.6×10^?3 M with detection limit of 6.0×10^?8 M (signal/noise=3) for dopamine determination. Meanwhile, the optimized sensor for dopamine displayed a sensitivity of 83.8 μA mM^?1 and response time of 5 s with addition of 0.20 mM dopamine. In addition, DPV experiment revealed that interfering species such as ascorbic acid and uric acid could be effectively avoided. The RuO₂/MWNTs electrode presents stable, highly sensitive, favorable selectivity and fast amperometric response of dopamine.     

Determination of reducing sugars with a 2,4-dinitrophenolate-selective membrane electrode

A 2,4-dinitrophenolate-selective liquid-membrane electrode based on tetrapentylammonium dinitrophenolate dissolved in 2-nitrotoluene is described. The electrode exhibits rapid and near- Nernstian response to the activity of 2,4-dinitrophenolate anions in the range 3×10^?5 ?1×10^?2 M. The response is unaffected by pH in the range 7.5–12.5. The electrode has been successfully applied to the kinetic potentiometric determination of fructose, glucose and galactose at 60°C and of fructose in the presence of glucose and galactose at 30°C. The electrode can be used for the potentiometric determination of glucose and fructose after completion of the reaction with excess of 2,4-dinitrophenolate ions and of sucrose after acid hydrolysis. Mixtures of glucose, fructose and sucrose in aqueous solutions or honey samples can be determined by the proposed procedures with an average error of about 2%.     

Determination of pesticides in vegetable samples using an acetylcholinesterase biosensor based on nanoparticles ZrO2/chitosan composite film

An amperometric pesticides inhibition biosensor has been developed and used for determination of pesticides in vegetable samples. To eliminate the interference of ascorbic acid, multilayer films of polyelectrolyte (chitosan/polystyrensulfonate) were coated on the glass carbon electrode. Then, acetylcholinesterase was immobilized on the electrode based on surface-treated nanoporous ZrO₂/chitosan composite film as immobilization matrix. As a modified substrate, acetylthiocholine was hydrolysed by acetylcholinesterase and produced thiocholine which can be oxidized at +700?mV vs. SCE. Pesticides inhibit the activity of enzyme with an effect of decreasing of oxidation current. The experimental conditions were optimized. The electrode has a linear response to acetylthiocholine within 9.90?×?10^?6 to 2.03?×?10^?3?M. The electrode provided a linear response over a concentration range of 6.6?×?10^?6 to 4.4?×?10^?4?M for phoxim with a detection limit of 1.3?×?10^?6?M, over a range of 1.0?×?10^?8 to 5.9?×?10^?7?M for malathion, and over a range of 8.6?×?10^?6 to 5.2?×?10^?4?M for dimethoate. This biosensor has been used to determine pesticides in a real vegetable sample.     

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.     

Highly Sensitive Electrochemical Sensor for Nitric Oxide Using the Self‐Assembled Monolayer of 1,8,15,22‐Tetraaminophthalocyanatocobalt(II) on Glassy Carbon Electrode

Glassy carbon (GC) electrode modified with a self‐assembled monolayer (SAM) of 1,8,15,22‐tetraaminophthalocyanatocobalt(II) (4α‐Co^IITAPc) was used for the selective and highly sensitive determination of nitric oxide (NO). The SAM of 4α‐Co^IITAPc was formed on GC electrode by spontaneous adsorption from DMF containing 1 mM 4α‐Co^IITAPc. The SAM showed two pairs of well‐defined redox peaks corresponding to Co^III/Co^II and Co^IIIPc^?1/Co^IIIPc^?2 in 0.2 M phosphate buffer (PB) solution (pH 2.5). The SAM modified electrode showed excellent electrocatalytic activity towards the oxidation of nitric oxide (NO) by enhancing its oxidation current with 310 mV less positive potential shift when compared to bare GC electrode. In amperometric measurements, the current response for NO oxidation was linearly increased in the concentration range of 3×10^?9 to 30×10^?9 M with a detection limit of 1.4×10^?10 M (S/N=3). The proposed method showed a better recovery for NO in human blood serum samples.     

Potentiometric PVC membrane sensor for the determination of phenylephrine hydrochloride in some pharmaceutical products

A new PVC membrane electrode for the determination of phenylephrine hydrochloride based on the formation of an ionassociation complex of phenylephrine hydrochloride with the phosphotungstate counter anion as an electroactive material dispersed in a PVC matrix is described. The sensor shows a fast, stable, near-Nernstian response for 1.0 × 10^?5 to 1.0 × 10^?1 M phenylephrine hydrochloride at 25 °C over the pH range of 3.5–8.0 with a cationic slope of 58.1 ± 0.6 mV decade^?1. The electrode was successfully used for potentiometric determination of phenylephrine hydrochloride in some pharmaceutical drugs.     

Simultaneous Determination of Hydroquinone and Catechol at a Glassy Carbon Electrode Modified with Multiwall Carbon Nanotubes

A simply and high selectively electrochemical method for simultaneous determination of hydroquinone and catechol has been developed at a glassy carbon electrode modified with multiwall carbon nanotubes (MWNT). It was found that the oxidation peak separation of hydroquinone and catechol and the oxidation currents of hydroquinone and catechol greatly increase at MWNT modified electrode in 0.20 M acetate buffer solution (pH 4.5). The oxidation peaks of hydroquinone and catechol merge into a large peak of 302 mV (vs. Ag/AgCl, 3 M NaCl) at bare glassy carbon electrode. The two corresponding well‐defined oxidation peaks of hydroquinone in the presence of catechol at MWNT modified electrode occur at 264 mV and 162 mV, respectively. Under the optimized condition, the oxidation peak current of hydroquinone is linear over a range from 1.0×10^?6 M to 1.0×10^?4 M hydroquinone in the presence of 1.0×10^?4 M catechol with the detection limit of 7.5×10^?7 M and the oxidation peak current of catechol is linear over a range from 6.0×10^?7 M to 1.0×10^?4 M catechol in the presence of 1.0×10^?4 M hydroquinone with the detection limit of 2.0×10^?7 M. The proposed method has been applied to simultaneous determination of hydroquinone and catechol in a water sample with simplicity and high selectivity.     

Construction of a new solid-state U(VI) ion-selective electrode based on polypyrrole conducting polymer

In this study, a potentiometric sensor based on a pencil graphite electrode (PGE) coated with polypyrrole doped with uranyl zinc acetate (termed PGE/PPy/U) have been prepared for potentiometric determination of uranyl in aqueous solutions. Electropolymerization reaction for preparing of U(VI) sensor electrode was carried via applying a constant current of 1.0 mA on PGA working electrode in a solution containing 8.0 mM pyrrole and 0.8 mM ZnUO₂(CH₃COO)₄ salt. The constructed electrode displayed a linear and near Nernstian response (22.60 ± 0.40 mV/decade) to U(VI) ions in the concentration range of 1.0 × 10^?6–1.0 × 10^?2 M. A detection limit of 6.30 × 10^?7 M and a fast response time (≤12 s) was observed during measurements. The working pH range of the electrode was 4.0–8.0 and lifetime of the sensor was at least 60 days. The electrode revealed good selectivity with respect to many cations including alkali, alkaline earth, transition and heavy metal ions. The introduced uranyl electrode was used for measurement of U(VI) ion in real samples without any serious inferences from other ions.     

Electrochemical Behavior and Determination of Phenylephrine at Silicate Nanotubes Modified Electrode

A novel Silicate nanotubes (SNTs) modified glass carbon (GC) electrode was prepared and used to study the electrochemcial behavior of phenylephrine (PHE) and determine it. The enhanced electrochemical response of PHE at SNTs modified electrode was observed as compared with bare GC electrode. This proposed method displayed a broad linear range and a lower detection limit for PHE. The linear range was from 8 × 10^?8 M to 2 × 10^?5 M with the detection limit of 1 × 10^?8 M. The electrode could be easily regenerated and exhibited high stability and good selectivity. This method was successfully applied to the determination of PHE in drug samples with satisfactory result. The strategy presented here opens a new way for the development of nanoelectronic devices or electrochemical sensors based on SNTs.     

Development of Nalbuphine‐Selective Membrane Electrode and Its Applications in Pharmaceutical Analysis

Abstract

A nalbuphine ion‐selective PVC membrane electrode based on ion‐pair complex of nalbuphine with tetra phenyl borate was prepared with di‐butyl sebacate as a plasticizer. The electrode exhibits a linear response with a Nernstain slope 59.6 mV decate^?1 at 25°C with the concentration range of 1×10^?6?1×10^?2 M nalbuphine. The electrode response was not sensitive to pH changes from 3.5–7 and not affected by possible interfering species such as common inorganic cations, sugars and amino‐acids. The electrode shows good stability, reproducibility and fast response. These characteristics of the electrode enable it to be used successfully for the determination of nalbuphine hydrochloride in pure form and in pharmaceutical preparations.     

Polarographic determination of pilocarpine using the catalysed pre-wave of nickel(II)

On the basis of a detailed study of the pilocarpine-induced nickel(II) pre-wave using various polarographic techniques, an electrode process mechanism is proposed in which the formation of a catalytic complex between aquo-nickel(II) and veronalate-nickel(II) on the one hand and unprotonated pilocarpine adsorbed on the electrode surface on the other is followed by the reduction of nickel(II) in the complex and the release of the catalytic ligand. The pre-peak recorded by differential-pulse polarography in the system 1 × 10^?3 M Ni(II)-1 × 10^?2 M sodium veronal, nitric acid (pH 8.5) (with ionic strength maintained at 0.2 with sodium nitrate) can be used for quantitative determination of pilocarpine at concentrations in the range 2.5 × 10^?7-8 × 10^?6 M.     

Zinc-Selective Membrane Electrode Based On 5, 6, 14, 15-Dibenzo-l, 4-Dioxa-8, 12-Diazacyclopentadecane-5, 14-Diene

ABSTRACT

A new PVC membrane for zinc ions based on DBDA15C4 as membrane carrier was prepared. The electrode shows a linear stable response over a wide concentration range (5.0 × 10^?5-1.0 × 10^?1 M) with a slope of 22 mV/decade and a limit of detection of 3.0 × 10^?5 M (2.0 μg/ml). It has a very short response time of less than 5 s and can be use for at least 11 months without any divergence in potential. The zinc ion-selective electrode exhibited very good selectivities with respect to alkali, alkaline earth and some transition and heavy metal ions and could be used in a pH range 1.5-7.0. It was successfully applied for the direct determination of zinc in a pharmaceutical sample and, as an indicator electrode, in potentiometric titration of Zn²⁺ ions.     

Novel PVC-based coated graphite electrode for selective determination of quinoline yellow

Novel coated graphite electrode (CGE) for the determination of quinoline yellow (QY), an artificial food colorant, was evaluated based on the use of tetraphenylphosponium-QY ion-pair complex as the electroactive substance. The electrode revealed linear emf-pQY response over wide concentration ranges (1.0 × 10^?1 ～ 5.0 × 10^?5 M) with a slope ?30.1 ± 0.2 mV decade^?1 and a limit of detection of 4.0 × 10^?5 M. The electrode showed good stability, reproducibility and fast response (<5 s). It can be used in wide pH range (4.7–10.7) and was successfully applied to determination of quinoline yellow in artificial mixtures and commercial soft drinks. The results obtained with the electrode were in good agreement with the value obtained by using HPLC measurements, as an official method.