Selective Liquid Membrane Electrode Research Articles

Rapid Monitoring of Copper Over a Wide Concentration range by High-Sensitive Potentiometric Membrane Electrode Based on 1-cyano-1-piperidino-2(N- piperidino methyl)-cyclo hexane

n this paper, 1-cyano-1-piperidino-2(N- piperidino meth-yl)-cyclohexane was synthesized. The lowest-energy conformer of this molecule (Ligand) with axial and equatorial forms of cyanide toward cyclohexane and local minima corresponding to their complexes with various ions were obtained using Monte Carlo procedure by Molecular Mechanics with MMFF94 method. The calculated results of the Gibbs free energy of the reaction using density functional theory (DFT) show that the thermodynamic reactivity of complexation of copper ion with studied ligand is the best. Finally, a selective and sensitive copper-ion selective liquid membrane electrode for potentiometric monitoring of ultra-trace amounts of Cu2+ was prepared by using 1-cyano-1-piperid-ino-2(N- piperidino methyl)-cyclohexane as an excellent ionophore. This electrode exhibits a Nernstian response for Cu2+ ions over a con-centration range (1.5 × 10-2 to 1.0 × 10-8 mol L-1) with a slope of 28.4±0.4 mV per decade. The limit of detection of the sensor is 6.3 × 10-9 mol L-1. The sensor has a relatively fast response time (<10 s) and a useful working pH range of 5.0–8.5. Interference of some cations was also evaluated. The practical utility of the Cu2+ ion sensor has been demonstrated by using it as an indicator electrode in potentiomet-ric titration of Cu2+ with EDTA and for direct determination of Cu2+ in well water samples.

Preparation of a ticlopidine potentiometric sensor and its application to pharmaceutical and biological analysis

Ticlopidine (Tic) ion selective liquid membrane electrode was constructed from poly (vinyl chloride) containing Tic-tetraphenylborate (Tic-TPB) as the sensing element in the presence of dioctylphthalate (DOP) as the plasticizing solvent mediator. The electrode shows nearly Nernstian response for the drug over the concentration range of 1.0×10−2–5.0×10−5M with cationic slope of 58.23mV per concentration decade, and the response time is very short (≤10s). The electrode potential is nearly stable over the pH range 3.8–5.4. The electrode exhibits good selectivity for the Tic with respect to a large number of inorganic ions, amino acids and some pharmaceutical substances. The sensor successfully was used for the determination of Tic in pharmaceutical and biological samples. The average recovery and RSD for the analysis of Tic in pharmaceutical and biological samples using the proposed method obtained 101.04, 98.90% and 1.14, 1.39%, respectively. The results are in good agreement with those obtained by voltammetry method.

BEHAVIOR OF A POLYMERIC LIQUID MEMBRANE ION- SELECTIVE ELECTRODE FOR CHLORIDE ION

Chloride selective polymeric liquid membrane electrode has been developed by using Bis-(2-ethylhexyl) Sebacate (DOS) as plasticizer and 2-[5-(4-nitrophenyl) furyl]-4,5-diphenyl imidazole (FFDFIN) as ionophore. Some parameters of evaluation of the electrode are presented in this work. The constructed electrode showed fast potentiometric response to chloride ion in the concentration range from 10-6 to 10-2 mol.dm-3 with Nernstian slope of -63.43 ± 0.85 mV/decade, response time of 25 seconds and life time of 15 days.

Determination of Apparent Formation Constants of Eu(III) with Humic Substances by Ion Selective Liquid Membrane Electrode

This is the novel measurement of the apparent formation constants of trivalent lanthanide with humic substances by potentiometric titration using an ion selective electrode (ISE) consisting of bis(diphenylphosphoryl)methane as an ionophore. The ISE prepared exhibited a Nernstian response to the Eu3+ concentration in the test solutions in the presence of humic acid and fulvic acid. The effect of the solution conditions, including the pH, initial metal and humic substance concentrations, and ionic strength, on the formation constants was examined. The present formation constants were compared with the reported data using solvent extraction method.

<b>Potentiometric determination of K<sup>+</sup> ions using a K<sup>+</sup>-selective electrode with macrocyclic liquid membrane</b>

This paper describes analytical applications of K + -selective liquid membrane electrode. The membrane is the solution of the active complex formed by the K + ions with dibenzo-18-crown-6 ionophore (DB-[18]-C-6) extracted in propylenecarbonate (PC). Successful application of the developed electrode for K + ions determination in aqueous solution and samples of commercial mineral water by direct potentiometry is presented. KEY WORDS : K+-selective electrode, Macrocyclic ligand, Potentiometry Bull. Chem. Soc. Ethiop. 2008 , 22(2), 295-299.

Tetrachloroferrate(III)-selective liquid membrane electrode based on crystal violet

An extract of crystal violet-tetrachloroferrate(III)in nitrobenzene was used to prepare a tetrachloroferrate(II)()-selective liquid membrane electrode with a poly(vinyl chloride) support. The optimal conditions to determine 2.5 x 10 -5- 5.0 x 10-2M iron(III) as tetrachloroferrate(III) (anionic slope 56 mV/decade, detection limit 7.9 x 10-6M) were found to be 4.0-5.5. M total chloride in 0.75 1.5 M hydrochloric acid. The electrode was reliably applied to determine iron in human blood, haematite and mineralized vitamin syrup by direct potentiometry, standard and sample additions as well as standard subtrac- tion techniques.

Potentiometric determination of tanatalum with a hexafluorotantalate(V) -selective liquid membrane electrode

Brilliant Green-hexafluorotantalate(V) extract in nitrobenzene was used as electroactive material to prepare a hexafluorotantalate(V) -selective liquid membrane electrode with a PVC support. The electrode body was made from concentric polypropylene tubes which were joined by a cork. The liquid membrane electrode was connected with fluoride-selective electrode as internal reference and ground glass diaphragm ( Ag AgCl ) electrode as external reference electrode to obtain a complete cell assembly for the potential measurements. The concentrations of sulphuric and hydrofluoric acid, for the optimum response of the electrode to hexafluorotantalate(V), were found to be 1 M each in the test solutions. The electrode was found to respond to hexafluorotantalate(V) in the concentration range of 2.0 × 10 −6−1.0 × 10 −2 M tantalum(V) with a slope of − 59 mV per decade and detection limit of 3.7 × 10 −7 M tantalum(V) within 20–120 s. The effects of forty diverse ions on the electrode response to the hexafluorotantalate(V) have been studied and the electrode has been found to be highly selective to hexafluorotantalate(V). The newly developed liquid membrane electrode has been applied successfully to the determination of tantalum in tantalite-columbite ores by direct, sample addition, standard addition, and Gran's plot potentiometric techniques.

Selective Liquid and (Vinyl-Chloride) Pentoxyverine Membrane Electrodes - Their Preparation and Use for the Potentiometric Determination of Pentoxyverine Citrate

Abstract The use of liquid and poly(vinyl-chloride) membrane electrodes which are sensitive and reasonably selective for pentoxyverine determination is described here. The electrodes are based on the use of pentoxyverine-picrate, pentoxyverine-picrolonate and pentoxyverine-tetraphenylborate ion association complexes as electroactive materials in nitrobenzene or in poly(vinyl chloride) matrix. These electrodes show near Nernstian response values in different concentration ranges, depending on the nature of the used counter-ions, at 3.3–7.8 pH range. Potentiometric determination of pentoxyverine citrate with use of these electrodes gives good results which later on are compared with those obtained by non-aqueous titration.

Some analytical applications of Cu2+ selective liquid membrane electrode

Some analytical applications of Cu2+ selective liquid membrane electrode

Potentiometric and conductometric determination of ammonium by gas-diffusion flow injection analysis

Considerable enhancement of selectivity in the potentiometric and conductometric determination of ammonium is provided by gas-diffusion separation in flow injection analysis. Ammonium and potassium selective liquid membrane electrodes can be used for determinations in the concentration range 10−7–10−2 mol/l with high precision and fast sample throughput. No interferences are encountered in the presence of ionic species and molecules that likely adsorb when the sensors are in direct contact with the sample. The selectivity over volatile amines is enhanced due to kinetic discrimination. Conductometric detection is shown to be as sensitive as the potentiometric detection. A major advantage, however, is the linear rather than logarithmic relationship between concentration and conductivity.

Response of Liquid-Membrane Calcium-Selective Electrodes to Calcium Ion Activity Steps

Abstract The results of fast Ca2+ activity step experiments using ionophore-and ion exchanger-based Ca2+-selective liquid membrane electrodes are presented. The recorded curves indicate that there is little dependence of electrode response on activity range or active electrode material. The response is shown to be dependent on the age of the ion-selective electrode (ISE) membrane. Impedance experiments performed show large fluctuations in the membrane bulk resistance over time. These results suggest that the membrane rapidly changes structure over a short period of time, which results in a slowing of the ISE response.

3,7‐Dioxaazelaamides as Ionophores for Lithium Ion Selective Liquid Membrane Electrodes

AbstractLipophilic neutral carriers were synthesized which show Li+/Na+ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li+ in blood serum within the clinical concentration range. A 1:1 Li+/ionophore complex of one representative (N,N,N′,N′‐tetracyclohexyl‐5,5‐dimethyl‐3,7‐dioxaazelaamide) has been prepared, and its structure was elucidated by X‐ray analysis.

Neutral carrier-based Na+-selective electrode for application in blood serum

The ionophore N,N,N′,N′-tetracyclohexyl-1,2-phenylenedioxydiacetamide (4) shows higher lipophilicity and superior Na+/K+ selectivity than the previously described N,N′-dibenzyl-N,N′-diphenyl-1,2-phenylenedioxydiacetamide (2). It is a suitable component of Na+-selective liquid membrane electrodes for the assay of Na+ in clinical analysers.

Permeability to sodium ions of the endolymph-perilymph barrier.

The endocochlear potential and Na+ activity in the endolymph were simultaneously measured with a double-barreled Na+ selective liquid membrane electrode. The modified Na+ conductance and permeability coefficient of the endolymph-perilymph barrier were calculated from the rate of change in the endolymph Na+ concentration relative to the Na+ electrochemical gradient across the barrier during permanent anoxia. In normal guinea pigs the Na+ conductance of the endolymph-perilymph barrier is approximately 5 times less than its K+ conductance. Exposure to noise or treatment with kanamycin suppresses the cochlear microphonics but does not result in significant alterations in the Na+ permeability of the endolymph-perilymph barrier. It is likely that the Na+ permeability of the endolymph-perilymph barrier is not involved in the physiological processes which lead to the cochlear damage produced by noise or kanamycin.

Potentiometry of Na+ in undiluted serum and urine with use of an improved neutral carrier-based solvent polymeric membrane electrode.

We present an improved Na+-selective liquid membrane electrode for measurement of Na+ concentrations in both undiluted serum and urine. The values for urinary Na+ obtained with the ion-selective electrode agree well with those obtained with the flame photometer. The correlation gives a standard residual deviation of +/- 2.7 mmol/L over the Na+ range of 25-280 mmol/L. In serum, this direct potentiometry yields Na+ concentrations 5.4% (SD 1.1%) higher than those obtained by atomic spectrometry and a standard residual deviation of +/- 1.1 mmol/L. Correction of these values for the volumes of protein and lipid leads to potentiometric values 1.2% (SD 0.7%) lower than those by flame photometry (residual standard deviation: +/- 1.0 mmol/L). Other factors that possibly contribute to this discrepancy are discussed.

Determination of Cholic Acids by Ion Selective Liquid Membrane Electrode in Pharmaceutical Products

Abstract An ion selective electrode based on a liquid membrane, constituted by a solution of tributylcetylphosphonium benzoate in nitrobenzene, is employed to determine cholic acids in pharmaceutical products by calibration curve and standard addition methods. The results are compared with those obtained with enzymatic and calorimetric methods. The proposed technique is simple, rapid and sufficently accurate.

Myocardial extracellular K + and H + increase and noradrenaline release as possible cause of early arrhythmias following acute coronary artery occlusion in pigs

In 22 young domestic pigs, after thoracotomy, the distal half of the ramus descendens anterior of the left coronary artery was occluded. This caused an ischemia affecting about 14% w w of both ventricles. The extracellular K + concentration ([K +]e) the extracellular H + activity ([H +]e, pH e) and the coronary arteriovenous noradrenaline differences were measured before and during coronary artery occlusion. [K +]e was measured with K +-selective PVC liquid membrane electrodes which were sewn on the epicardium of the left ventricle, pH e was measured using pH-selective bulb-type glass mini-electrodes which were fixed at a depth of 5 to 7 mm below the surface of the left ventricle. Plasma noradrenaline concentration was measured fluorimetrically using the trihydroxyindole method. About 10 s after the onset of occlusion [K +]e started to increase from a control value of 4.2 ± 0.7 meq/l. In 13 pigs after 2.5 ± 1.0 min at a [K +]e of 10.7 ± 1.9 meq/l a first early phase of ventricular arrhythmias (VA) began and ventricular fibrillation (VF) started after 3.2 ± 1.8 min of ischemia at 12.4 ± 2.8 meq/l. In 9 pigs after 3.4 ± 1.2 min at a [K +]e of 12.6 ± 3.8 meq/l the first early phase of VA started which ended after 8.3 ± 3.1 min at a [K +]e of 14.0 ± 2.9 meq/l without VF. In these 9 pigs after a period without any VA after 20.5 ± 7.5 min of ischemia at a [K +] e of 15.5 ± 2.9 meq/l the second early phase of VA began. It ended after 25.3 ± 12.3 min at a [K +)e of 17.7 ± 3.9 meq/l in 7 pigs with VE. Two pigs survived for some hours without VF. Noradrenaline was released into the coronary venous blood only during the first early phase of arrhythmia. Extracellular [H +] ([H +]e) started to increase 5 to 10 s after the onset of occlusion from a control value of 40 neq/l (pH 7.4) with an average rate of change of 50 to 60 neq/l/min reaching about 3000 neq/l (pH 5.5) after about 50 min of ischemia. Thereafter [H +]e further increased at a much lower rate. These data support the view that electrical inhomogeneity, known to induce arrhythmias following myocardial ischemia during the first early phase of VA, might be caused by a combined effect of [K +]e increase in the ischemic myocardium and noradrenaline release from the ischemic and non-ischemic myocardium, while during the second early phase the further [K +]e increase possibly in the border zone seems to be the main reason. The [H +]e increase does not seem to play an important rule in causing VA.

Stability of the calcium sulphate ion pair at the ionic strength of seawater by potentiometry

The stability of the ion pair CaSO4 was determined from measurement of the change in calcium ion activity with medium composition at constant ionic strength. A calcium selective PVC-matrix liquid membrane electrode was used to monitor the calcium ion activity. All measurements were performed at 1 atm, 25 ± 0.1°C and 0.7 M formal ionic strength. The evaluation of the stability constant depends on the degree of complexation between calcium and chloride and between sodium and sulphate. The dependence of KCaSO4, on KNaSO4 and KCaCl can be described by the following relations: KCaSO4=17.7 KCaCl+16.5 (KNaSO4=1.8) KCaSO4=18.8 KCaCl+17.3 (KNaSO4=2) for KCaCl=0–1A value of KCaSO4=25.4 is suggested.

Factors affecting the response time of a calcium selective liquid membrane electrode

Factors affecting the response time of a calcium selective liquid membrane electrode

Determination of potassium ion concentration in serum using a highly selective liquid-membrane electrode

A simple method for the direct determination of the K + concentration in undiluted blood serum is described. The reproducibility of single determinations using the readings after 60-sec contact of a valinomycin liquid-membrane electrode with the sample is 0.07 mequiv/1 K + (standard deviation). No corrections are needed for the presence of other ions in the sample solutions.