Ionic liquids with an anion of N-lauroyl sarcosinate in membranes of ion-selective electrode

The study considers solubility in water, extractivity, and electrode properties of ionic liquids (IL), lauroyl tetrahexylammonium (THALS) and tetraoctylammonium lauroyl sarcosinate (TOALS). The values of solubility, found by potentiometry using ion-selective membranes of PVC-electrodes (ISE) have appeared to be 3.0 ± 0.4 mM and 0.011 ± 0.005 mM, for THALS and TOALS, respectively. Both IL quantitatively recover nitrophenol (99.9%) into chloroform from aqueous solutions in the pH range from 2 to 12. The application of IL as the active components of PVC-ISE enables the determination of lauroyl sarcosinate anion in the concentration range 1 × 10^?2?C1 × 10^?4 M for THALS and 1 × 10^?2?C1 × 10^?5 M for TOALS and the determination of mononitrophenols, 2,4-dinitrophenols and picrates (1 × 10^?2 M?C1 × 10^?5 M). A solid-state sensor based on screen-printed electrode modified by TOALS IL has been proposed. The electrode has been used for the determination of 4-nitrophenol in the concentration range 1 × 10^?2?C1 × 10^?5 M, the operational stability of the electrode is 10 days.     

Solubility studies in formamide: II. Solubility product of silver iodate and standard electrode potential of silver—silver iodate electrode in formamide

The solubility and solubility product of silver iodate in formamide in sodium perchlorate solutions have been determined at 25, 30 and 35°C. The solubilities in pure formamide are found to be 2.169 × 10^?4, 2.488 × 10^?4, and 2.943 × 10^?4 mole I^?1, respectively, at these temperatures, and the corresponding solubility products are 4.609 × 10^?8, 6.053 × 10^?8, and 8.448 × 10^?8 mole² 1^?2. The standard potential of the Ag_(s)/AgIO_3(s)/IO₃^? electrode has been calculated and found to be 0.2562 V at 25°C. The mean activity coefficients of silver iodate at various rounded molarities of sodium perchlorate solutions, and the standard thermodynamic quantities for the process AgIO_3(s)åAg⁺ (solvated) + IO₃^? (solvated) have been calculated at these three temperatures.     

Cyanide ion selective solid contact electrode based on nickel complex of N,N′-bis-(4-phenylazosalicylidene)-o-phenylene diamine ionophore

A cyanide ion selective poly(aniline) solid contact electrode based on nickel complex of N,N′-bis-(4-phenylazosalicylidene)-o-phenylenediamine ionophore was successfully developed. The electrode exhibits a good linear response of 58.7 mV/decade (at 20 ± 0.2°C, r ² = 0.998) with in the concentration range of 1 × 10^?1.0-1 × 10^?6.0 M cyanide. The composition of this electrode was: ionophore 0.300, polyvinylchloride 0.300, 2-nitrophenyloctyl ether 0.670 (mass). This 2-nitrophenyloctyl ether plasticizer provides the best response characteristics. The electrode shows good selectivity for cyanide ion in comparison with any other anions and is suitable for use with aqueous solutions of pH 4.6–6.3. The standard deviations of the measured emf difference were ±1.92 and ±1.87 mV for cyanide sample solutions of 1.0 × 10^?2 M and 1.0 × 10^?3 M, respectively. The stabilization time was less than 183 s and response time was less than 38 s.     

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.     

Etilefrine Plastic Membrane Electrodes Based on Individual and Mixed Ion-exchangers of Etilefrinium Phosphotungstate and Tetraphenylborate.

Abstract

Etilefrine hydrochloride (EfCl) selective PVC membrane electrodes based on Etilefrinium phosphotungstate (I), Etilefrinium tetraphenylborate (II) and a mixture of both (III) were prepared, The electrodes exhibited near Nernstian response over the concentration ranges 5.0 × 10^?6 - 1.0 × 10^?1, 6.3 × 10^?6 - 1.0 × 10^?1 and 6.3 × 10^?5 - 1.0 × 10^?1 M EfCl for electrodes I, II and III, respectively. The working pH ranges of electrodes I, II and III were 10 - 8.0, 10 - 7.5 and 10 - 7.5 and their isothermal coefficients were 0.00150, 0.00088 and 0.00072 V/°C, respectively. The electrodes showed good selectivity to EfCl with respect to many inorganic cations, sugars and amino acids. The standard additions method was used to determine EfCl in pure solutions and in pharmaceutical preparations.     

A Novel Adsorptive Square Wave Voltammetric Method for Pico Molar Monitoring of Lorazepam at Gold Ultra Microelectrode in a Flow Injection System by Application of Fast Fourier Transform Analysis

Abstract

This paper describes development of a new analysis system for determination of lorazepam by a novel square wave voltammetry method to perform a very sensitive method. The method used for determination of lorazepam involves measuring the changes in admittance voltammogram of a gold ultramicroelectrode (in 0.05 M H₃PO₄ solution) caused by adsorption of the lorazepam on the electrode surface. Variation of admittance in the detection process is created by inhibition of oxidation reaction of the electrode surface, by adsorbed lorazepam. Furthermore, signal-to-noise ratio is significantly increased by application of discrete fast Fourier transform (FFT) method, background subtraction, and two-dimensional integration of the electrode response over a selected potential range and time window. Also in this work, some parameters such as SW frequency, eluent pH, and accumulation time were optimized. Calibration plots are given for solutions containing 10^?6–10^?11 M of lorazepam. The detection limit is calculated to be 6.0 × 10^?12 M (～ 2 pg/ml). The relative standard deviation at concentration 3.0 × 10^?8 M is 6.1% for 5 reported measurements.     

Solubility studies in formamide: III. Solubility product of silver bromate and standard electrode potential of silver—silver bromate electrode in formamide

The solubility and solubility product of silver bromate in formamide in sodium perchlorate solutions have been determined at 25, 30 and 35°C. At these temperatures, the solubilities in pure formamide are found to be 1.837 × 10^?2, 1.967 × 10^?2, and 2.092 × 10^?2 moll^?1, respectively, and the corresponding solubility products are 3.375 × 10^?4, 3.869 × 10^?4, and 4.377 × 10^?4 mol² l^?2. The standard potentials of the Ag(s)/AgBrO₃(s)/BrO^?₃ electrode have been calculated and found to be 0.4997, 0.4948, and 0.4892 V, at 25, 30, and 35°C, respectively. The mean activity coefficients of silver bromate at various rounded molarities of sodium perchlorate solutions, and the standard thermodynamic quantities for the process AgBrO₃(s) → Ag⁺(solvated) + BrO^?₃(solvated) have been calculated at these three temperatures and compared with those for the process AgIO₃(s) → Ag⁺(solvated) + IO^?₃(solvated) in formamide.     

Zeolite-Modified Sol-Gel Electrode as an Electrochemical Sensor for Potentiometric Determination of Cesium Ions in Water Samples

Abstract

In this research, new electrodes were prepared by incorporating zeolite KY into sol-gel matrix. Calibration plot with Nernstian slope (58.6 ± 0.5 mV/decade) for cesium ion was observed over a linear range of about four decades of concentration (1.0 × 10^?5 to 1.0 × 10^?1 M, at 25°C). The sol-gel electrode shows detection limit of 7.3 × 10^?6 M. The influences of membrane composition, the pH of the test solution, and the interfering ions on the electrode performance were investigated. The effect of temperature on the electrode response showed that the temperature higher than 60°C deteriorates the electrode performance. The proposed electrode has high mechanical and thermal stability with a low isothermal temperature coefficient, and it is 0.00018 V/°C. It has a short response time (10 s) and can be used for more than 6 months without any considerable divergence in the potentials. The selectivity coefficients for Cs⁺ ion with respect to alkali, alkaline earth, ammonium, and some heavy-metal ions were investigated. The results of application show that the electrode can be used successfully in determination of Cs⁺ ions in various water samples.     

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).     

Preparation of Cu (II) imprinted polymer electrode and its application for potentiometric and voltammetric determination of Cu (II)

The Cu (II) imprinted polymer glassy carbon electrode (GCE/Cu-IP) was prepared by electropolymerization of pyrrole at GCE in the presence of methyl red as a dopant and then imprinting by Cu²⁺ ions. This electrode was applied for potentiometric and voltammetric detection of Cu²⁺ ion. The potentiometric response of the electrode was linear within the Cu²⁺ concentration range of 3.9 × 10^?6 to 5.0 × 10^?2 M with a near-Nernstian slope of 29.0 mV decade^?1 and a detection limit of 5.0 × 10^?7 M. The electrode was also used for preconcentration anodic stripping voltammetry and results exhibited that peak currents for the incorporated copper species were dependent on the metal ion concentration in the range of 1.0 × 10^?8 to 1.0 × 10^?3 M and detection limit was 6.5 × 10^?9 M. Also the selectivity of the prepared electrode was investigated. The imprinted polymer electrode was used for the successful assay of copper in two standard reference material samples.     

Determination of Pseudoephedrine Hydrochloride in Some Pharmaceutical Drugs by Potentiometric Membrane Sensor Based on Pseudoephedrine–Phosphotungstate Ion Pair

Abstract

An ion-selective electrode (ISE) was developed for the rapid determination of pseudoephedrine hydrochloride (PSEHCl) in pharmaceutical preparations. The electrode incorporates a PVC membrane with a pseudoephedrine–phosphotungstate ion pair complex. The influences of membrane composition, temperature, pH of the test solution, and the interfering ions on the electrode performance were investigated. The sensor exhibits a Nernstian response for pseudoephedrine hydrochloride ions over a relatively wide concentration range (1.0 × 10^?1 to 1.0 × 10^?5 mol L^?1) with a slope of 56.2 ± 0.5 mV per decade at 25°C. It can be used in the pH range 4.0–10.5. The isothermal temperature coefficient of this electrode amounted to 0.0009 V/°C. The membrane sensor was successfully applied to determination of PSEHCl in its tablets and syrup.     

A Validated Voltammetric Procedure for Quantification of the Antifungal Drug Griseofulvin in Bulk Form,Tablets, and Biological Fluids at a Mercury Electrode

Abstract

Griseofulvin is an antifungal antibiotic used to treat various pathogenic mycotic diseases. The voltammetric behavior of griseofulvin at a hanging mercury drop electrode in Britton‐Robinson buffers of pH 2–11.5 was studied and discussed. A fully validated sensitive square‐wave adsorptive cathodic stripping voltammetric procedure was described for direct determination of bulk griseofulvin substance. The procedure was based on the reduction of the >C?O double bond of griseofulvin molecule following its preconcentration onto a hanging mercury drop electrode in a Britton‐Robinson buffer of pH 10. Limits of detection (LOD) and quantitation (LOQ) of 5.8×10^?10 M and 1.93×10^?9 M bulk griseofulvin were achieved, respectively. The proposed stripping voltammetric procedure was successfully applied to assay griseofulvin in tablets and in spiked human serum and urine samples. LOD of 8.65×10^?10 M and 6.6×10^?9 M and LOQ of 2.88×10^?9 M and 2.2×10^?8 M griseofulvin in spiked human serum and urine samples, respectively, were achieved.     

A New Amperometric Carbon Paste Enzyme Electrode for Ethanol Determination

Abstract

In this study, a new amperometric carbon paste enzyme electrode for determination of ethanol was developed. The carbon paste was prepared by mixing alcohol dehydrogenase, its coenzyme nicotinamide adenine dinucleotide (oxidized form, NAD⁺), poly(vinylferrocene) (PVF) that was used as a mediator, graphite powder and paraffin oil, then the paste was placed into cavity of a glass electrode body. Determination of ethanol was performed by oxidation of nicotinamide adenine dinucleotide (reduced form, NADH) generated enzymatically at +0.7 V. The effects of enzyme, coenzyme and PVF amounts; pH; buffer concentration and temperature were investigated. The linear working range of the enzyme electrode was 4.0×10^?4–4.5×10^?3 M, determination limit was 3.9×10^?4 M and response time was 50 s. The optimum pH, buffer concentration, temperature, and amounts of enzyme, NAD⁺ and PVF for enzyme electrode were found to be 8.5, 0.10 M, 37°C, 2.0, 6.0, and 12.0 mg, respectively. The storage stability of enzyme electrode at +4°C was 7 days. Enzyme electrode was used for determination of ethanol in two different wine samples and results were in good agreement with those obtained by gas chromatography.     

Construction and Performance Characteristics of a Chromotropate Sensing Plastic Membrane Electrode

Abstract

The lipophilic salt hexadecylpyridinium chromotropate (HDP)₂CT is used as ion exchanger in preparation of plastic membrane electrode sensitive to chromotropate anion. the electrode has the following main characteristics: slope ?29.0. mV decade_?1 (at 25°C), response time 5–10 sec, linear concentration response 7.9 × 10_?5?3.2 × 10_?2 M, usable pH range 5.0–10.5, isothermal temperature coefficient 0.00037 V/°C and maximum working temperature 52°C. the electrode is very selective for chromotropate towards many inorganic and organic anions. the solubility product of (HDP)₂CT is determined potentiometrically using the concerned electrode. the standard addition method is used to determine CT_?2 in presence of KCl (0.1 M) with satisfactory results, confidence limit of the mean value (95 % probability) was (1.78 ± 0.03) × 10_?11.     

Amperometric Determination of Bilirubin with Flow Injection Analysis System

Abstract

The amperometric method using the flow injection system has been developed for the determination of bilirubin. Bilirubin is oxidized to biliverdin at the glassy carbon working electrode. The optimum conditions were investigated. Linear calibration curve was obtained between 1.0×10⁶ and 1.0×10^?3M, with a sampling rate of 20 samples h^?1 and a relative standard deviation of 3.2%. The limit of detection is 4.0×10^?7M. Interference of hemoglobin was not observed.     

Sequential extraction partitioning of metals,sulfur, and phosphorus in bottom ash from a coal-fired power plant

Abstract

The herbicide trifluralin was analysed by adsorptive stripping voltammetry on a glassy carbon electrode. The linear concentration range was 2.5 × 10^?7 M – 1.25 × 10^?6M when using 5-min preconcentration at open circuit conditions in Britton-Robinson buffer of pH 7.0. The detection limit of trifluralin was 2.5 × 10^?8M. The relative standard deviation was 3.3% at a concentration of 1.0 × 10^?6M (n=5). The method was applied to the determination of trifluralin in soil with good recovery.     

Determination of mercury ions on a diphenylcarbazone bulk modified graphite electrode

A bulk modified electrode prepared by pressing a mixture of carbon powder and diphenylcarbazone at 15.2 MPa was used for the determination of mercury in aqueous solutions. Mercury(II) ions are concentrated by complexation with the modifier in acidic (HNO₃) solution. After exchange of the medium for 1 M HCl and 1 M CaCl₂, mercury is reduced at ?0.8 V vs. SCE. The signal is generated by anodic stripping in the differential-pulse mode. The calibration graph is linear in the range 5×10^?8?5× 10^?6 M with a relative standard deviation of 7%. After enrichment for 10 min the detection limit is 5×10^?8 M. Silver, chromate and strong complexing agents interfere. The use of the electrode to determine the labile fraction in mercury speciation is discussed.     

Anodic Voltammetric Behavior and Determination of Antihistaminic Agent: Fexofenadine HCl

Abstract

A voltammetric study of the oxidation of fexofenadine HCl (FEXO) has been carried out at the glassy carbon electrode. The electrochemical oxidation of FEXO was investigated by cyclic, linear sweep, differential pulse (DPV), and square wave (SWV) voltammetry using glassy carbon electrode. The oxidation of FEXO was irreversible and exhibited diffusion‐controlled process depending on pH. The dependence of intensities of currents and potentials on pH, concentration, scan rate, nature of the buffer was investigated. Different parameters were tested to optimize the conditions for the determination of FEXO. For analytical purposes, a very well resolved diffusion‐controlled voltammetric peak was obtained in Britton‐Robinson buffer at pH 7.0 with 20% constant amount of methanol for DPV and SWV techniques. The linear response was obtained in supporting electrolyte in the ranges of 1.0×10^?6–2.0×10^?4 M with a detection limit of 6.6×10^?9 M and 5.76×10^?8 M and in serum samples in the ranges of 2.0×10^?6–1.0×10^?4 M with a detection limit of 8.08×10^?8 M and 4.97×10^?8 M for differential pulse and square wave voltammetric techniques, respectively. Only square wave voltammetric technique can be applied to the urine samples, and the linearity was obtained in the ranges of 2.0×10^?6–1.0×10^?4 M with a detection limit of 2.00×10^?7 M. Based on this study, simple, rapid, selective and sensitive two voltammetric methods were developed for the determination of FEXO in dosage forms and biological fluids. For the precision and accuracy of the developed methods, recovery studies were used. The standard addition method was used for the recovery studies. No electroactive interferences were found in biological fluids from the endogenous substances and additives present in tablets.     

Graphite disk Lanthanum(III)-selective electrode based on Kryptofix-22DD

ABSTRACT

A novel ion-selective electrochemical sensor based on kryptofix-22DD (1,10-didecyl-1,10-diaza-18-crown-6) as an ionophore was constructed for determination of lanthanum(III) cation in solutions. The D-Optimal Mixture Design(D-OMD) was used as an experimental design strategy for optimal formulation of the membrane ingredients, and the actual values of the ingredients were compared with their predicted values. The amounts of the ionophore, plasticizer, PVC, and also the graphite powder which influence the performance of the fabricated electrode were analyzed using D-OMD. A non-linear relationship was observed between the slope of the electrochemical response of the electrode and these variables and the interaction between the variables as well. The experimental results showed that the amount of the ionophore has the most positive effect on the electrochemical response of the electrode. The constructed electrode exhibits a Nernstian slope (20.60 ± 0.21 mv.decade^?1) in a wide linear concentration range from 1.0 × 10^?7 to 1.0 × 10^?1 M with respect to La³⁺ cation at pH range of 4.0 to 6.0, and its detection limit was found to be:0.8 × 10^?7M. The selectivity of the proposed electrode towards some of the metal cations present in lanthanum(III) cation solutions was tested, and the experimental results showed a good selectivity towards this metal cation.     

Determination of coumarins by voltammetric techniques in micellar and emulsified media

An electroanalytical study of the oxidation processes of umbelliferone and hymecromone at a glassy carbon electrode in micellar solution and emulsified medium by different voltammetric techniques is described. The non-ionic surfactant Triton X-405 in acetate-buffered medium at pH 4.8 was found to be the most suitable. Different ranges of linearity were obtained in the micellar solutions, depending on the technique used; the limits of determination for differential pulse voltammetry (DPV) at a stationary electrode were 2.9×10^?6 mol l^?1 and 3.3×10^?6 mol l^?1 for umbelliferone and hymecromone, respectively. In the emulsified medium formed with a mixture of toluene and ethyl acetate (3:2), the oxidation processes yielded similar results. With DPV, linear calibration plots were obtained in the ranges 1.0×10^?5–9.0×10^?7 mol l^?1 umbelliferone and 1.0×10^?5–2.0×10^?6 mol l^?1 hymecromone. The media used are predominantly aqueous so that special reference electrodes and solvent purification are not needed.