Ion-selective Membrane Electrodes Research Articles

Overcoming Pitfalls in Boundary Elements Calculations with Computer Simulations of Ion Selective Membrane Electrodes.

Finite difference analysis of ion-selective membranes is a valuable tool for understanding a range of time dependent phenomena such as response times, long and medium term potential drifts, determination of selectivity, and (re)conditioning kinetics. It is here shown that an established approach based on the diffusion layer model applied to an ion-exchange membrane fails to use mass transport to account for concentration changes at the membrane side of the phase boundary. Instead, such concentrations are imposed by the ion-exchange equilibrium condition, without taking into account the source of these ions. The limitation is illustrated with a super-Nernstian potential jump, where a membrane initially void of analyte ion is exposed to incremental concentrations of analyte in the sample. To overcome this limitation, the two boundary elements, one at either side of the sample-membrane interface, are treated here as a combined entity and its total concentration change is dictated by diffusional fluxes into and out of the interface. For each time step, the concentration distribution between the two boundary elements is then computed by ion-exchange theory. The resulting finite difference simulation is much more robust than the earlier model and gives a good correlation to experiments.

Fluorinated tripodal receptors for potentiometric chloride detection in biological fluids

Fluorinated tripodal compounds were recently reported to be efficient transmembrane transporters for a series of inorganic anions. In particular, this class of receptors has been shown to be suitable for the effective complexation of chloride, nitrate, bicarbonate and sulfate anions via hydrogen bonding. The potentiometric properties of urea and thiourea-based fluorinated tripodal receptors are explored here for the first time, in light of the need for reliable sensors for chloride monitoring in undiluted biological fluids. The ion selective electrode (ISE) membranes with tren-based tris-urea bis(CF3) tripodal compound (ionophore I) were found to exhibit the best selectivity for chloride over major lipophilic anions such as salicylate (logKCl−/Sal−pot=+1.0) and thiocyanate (logKCl−/SCN−pot=+0.1). Ionophore I-based ISEs were successfully applied for chloride determination in undiluted human serum as well as artificial serum sample, the slope of the linear calibration at the relevant background of interfering ions being close to Nernstian (49.8±1.7mV). The results of potentiometric measurements were confirmed by argentometric titration. Moreover, the ionophore I-based ISE membrane was shown to exhibit a very good long-term stability of potentiometric performance over the period of 10 weeks. Nuclear magnetic resonance (NMR) titrations, potentiometric sandwich membrane experiments and density functional theory (DFT) computational studies were performed to determine the binding constants and suggest 1:1 complexation stoichiometry for the ionophore I with chloride as well as salicylate.

Fabrication and optimization of Cu(II) ion selective membrane electrode

In this study, the fabrication, performance characteristics and application of a Cu(II) ion selective pyridine based thorium(IV) phosphate membrane electrode are studied. The membrane electrode exhibited a fast response time of 10 s, the wide linear response in the concentration of 1 × 10–1 to 1 × 10–7 M of Cu (II) ions with a slope of 27.60 mV/decade change in concentration and a lifetime of 4 months. The potentiometric response revealed that the potentials are independent of pH in the wide range of 3.0–6.5. It was also used as an indicator electrode in the potentiometric titration of Cu(II) ions using ethylenediamine tetraacetic acid, disodium salt.

Mathematical Modeling of Ion Selective Membrane Systems Subject to Electrical Polarization

Ion selective membrane (ISM) electrodes are widely used for selective ion sensing applications. We have, in our work, applied the ISM to modulate chemical concentrations utilizing the physical process of ion concentration polarization (ICP) for applications in neuroscience and neurotechnology.1 Here, we discuss physicochemical modeling of the ISM and adjacent phases under electrical polarization, focusing on key phenomena relating to ISM-based electrochemical modulation. We have developed several multidimensional models using Nernst-Planck-Poisson (NPP) with bulk reaction for multi-ion solute transport and full Navier-Stokes for solvent transport, making minimal simplifying assumptions. These models were solved using the finite element method (FEM) in COMSOL Multiphysics, and analytical solutions were derived for certain key situations. Previous approaches to modeling this system have relied on assumptions such as electroneutrality,2 excess supporting electrolyte,3 Butler-Volmer interfacial charge transfer,4 and equilibrium reactions.5 By avoiding these, we have been able to observe unique phenomena arising from ISM polarization, expanding the applicability of modeling predictions. Crucial transport properties of the membrane such as conductivity and primary ion transference can be evaluated using a one-dimensional model of chemical transport based on NPP with bulk reaction (shown in Figure 1A). We were able to show the process by which the membrane loses its selectivity for the primary ion upon significant depletion in the adjacent aqueous phase, upon which the membrane starts to transport interfering ions. In addition, we can show how limiting behavior and loss of selectivity occurs when the concentration of ions within the membrane are sufficiently polarized, above which point over-limiting current is carried by leaked counter ions such as chloride. Finally, the solutions to this model allows us to obtain critical information on the time-scale of the relevant processes that govern concentration changes. The dimensions of the ICP region are determined by three different processes, each with different characteristic length-scales: spontaneous convection, forced convection, and three-dimensional diffusion. To evaluate this, two-dimensional NPP with Navier-Stokes (Figure 1B-C) and three-dimensional axisymmetric NPP (Figure 1D-E) were solved for the cases of forced convection and three-dimensional diffusion respectively. Using these models, we were able to determine explicit relationships between variables such as flow rate and electrode dimensions, and the concentration profile of ions throughout the ICP region. In addition, we performed an experimental visualization of the forced convection model using fluorescence imaging of calcium-sensitive dye in a microfluidic channel (Figure 1F). These results are important not only for chemical modulation devices, but also for dynamic ISM sensors based on chronopotentiometry,6 coulometry,7 and amperometry.8

Complex-forming and ion-selective properties of bis(2-diphenylphosphorylalkyl)phenyl ethers of ethylene glycols. Crystal structures of cadmium complexes

New complexes of cadmium iodide with 1,3-bis[2-(diphenylphosphoryl)phenoxy]propane [CdL0I2], 1,2-bis[2-(diphenylphosphorylethyl)phenoxy]ethane [CdL1, 2I2], and 1,8-bis[2-(diphenylphosphorylethyl) phenoxy]-3,6-dioxaoctane [CdL3, 2I2] are synthesized and their IR spectra and crystal structures are studied. Electroanalytical characteristics of membranes of ion-selective electrodes based on L0, L1, 2, L3, 2, and known crown ethers are compared for cations of alkali, alkaline-earth, and transition metals. Ligand L3, 2 is the first podand with terminal diphenylphosphoryl fragments to exhibit selectivity with respect to the cadmium cation.

Optical Ion Sensing Platform Based on Potential-Modulated Release of Enzyme.

We report here on an optical ion sensing platform, in which a polymeric membrane ion-selective electrode (ISE) serves as not only a potentiometric transducer for ion activities in the sample solution but also a reference electrode for the potential-modulated release of enzyme from an iron-alginate-horseradish peroxidase (HRP) thin film modified working electrode. The ISE and working electrode are physically separated by a salt bridge. The dissolution of the HRP-embedded thin film can be triggered by the reduction of Fe3+, which is modulated by the potential response of the ISE to the target ion in the sample. The released enzyme induces the oxidation of its substrate mediated by H2O2 to produce a visual color change. With this setup, an optical ion sensing platform for both cations (e.g., NH4+) and anions (e.g., Cl-) can be obtained. The proposed platform provides a general and versatile visual-sensing strategy for ions and allows optical ion sensing in colored and turbid solutions.

Preparation of poly(2-methylaniline)V(III) tungstate nanofiber and its application as indicator electrode by diffusion phenomenon

Currently, polymer-inorganic composites became inspiration for the design of advanced synthetic materials. Exfoliation/intercalation method was used for the preparation of poly(2-methylaniline)V(III) tungstate nanofiber (POT-VOWO4) composite. The poly(2-methylaniline) into V(III) tungstate was mixed by different volume ratios. A characterization of composite was carried out by XPS, SEM, XRD, FTIR and simultaneous TGA studies. This composite was employed as sensor element in the preparation of ion selective membrane electrode in electrometric titrations by diffusion mechanism. By experiment, it was found that electrode had linear range (1.0×10−1M to 6.0×10−6M), good Nernstian response of 30.4mV/decade change of Hg2+ concentration with working pH range of 3.0–8.0 having short response time of 20s. This electrode was used as indicator electrode for real samples analysis.

An uranyl solid state PVC membrane potentiometric sensor based on 4,13-didecyl-1,7,10,16-tetraoxa-4,13- diazacyclooctadecane and its application for environmental samples

ABSTRACTAn ion-selective membrane electrode based on 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (Kryptofix 22DD) incorporated into a polyvinyl chloride (PVC) membrane has been constructed. The electrode was prepared by a membrane containing dibutylphetalate (DBP) as plasticiser, Kryptofix 22DD as an ionophore, graphite powder as an additive and PVC as a matrix. Under the optimised membrane composition, the constructed electrochemical sensor shows the best response characteristics with a Nernstian behaviour over the concentration range of 1.0 × 10−4–1.0 × 10−1 mol L−1 of solution, with a detection limit of 1.20 × 10−5 mol L−1. The electrode is applicable in the pH range of 1.5–4. It has a fast response time of about 10 s and can be used for at least 12 weeks without any considerable spellcheck in its potential response. The fabricated electrode reveals a good selectivity towards the ion in the presence of several cations in solution and also, it could be applied for determination of this ion in real samples.

Phenoxy-substituted boron subphthalocyanine as a ionophore of ion-selective electrodes

Phenoxy-substituted boron subphthalocyanine was synthesized and studied as an ionophore of plasticized polyvinyl chloride membranes of ion-selective electrodes. The electrodes exhibit reversible response to dobutamine, demonstrating the cation function, as well as reversible response to the salicylate anion. The effects of concentration of the ionophore (0.2–5 wt %) and ionic components (sodium tetraphenylborate, TPhBNa, and tributylhexadecylphosphonium bromide, TBGDPBr), including ionic liquids (ILs), such as diphenylbutylethylphosphonium bis(triflyl)imide, diphenylbutylethylphosphonium hexafluorophosphate, and 1,3-dihexadecylimidazolium chloride, as well as plasticizers, such as ortho-nitrophenyloctyl ether and diethyl sebacate, on the electrochemical characteristics of membranes were studied. For the electrode containing 2% of the phenoxy-substituted boron subphthalocyanine in dobutamine and salicylate solutions, the slopes of the electrode function were 36 ± 1 mV/dec and–46 ± 3 mV/dec and the limits of detection (LODs) were 4 × 10–5 M and 3 × 10–4 M, respectively. The addition of an ionic liquid containing the diphenylbutylethylphosphonium cation and the bis(triflyl)imide and hexaflurophosphate anions to the membrane composition had no effect on the response of membrane electrodes to both dobutamine and salicylate. The use of phenoxy-substituted boron subphthalocyanine in an amount of 2% and the TPhBNa additive significantly improved sensor characteristics: the slope of the electrode function (S) for the dobutamine-selective electrode was (54 ± 1) mV/dec and LOD was 1 × 10–5 M. Dobutamine can be determined in the presence of dopamine, adrenalin, and glucose. Electrodes based on 2% phenoxy-substituted boron subphthalocyanine and 0.5% (C16H33)2ImCl, or TBGDPBr in salicylate solutions demonstrate the slope of the electrode function close to the theoretical one and a low limit of detection: S = (–59 ± 1) mV/dec, LOD = 2 × 10–5 M and S = (–57 ± 1) mV/dec, LOD = 4 × 10–5 M, respectively. The anti-Hofmeister selectivity of sensors was observed. The electrode based on phenoxy-substituted boron subphthalocyanine and (C16H33)2ImCl was used for the assay of acetylsalicylic acid in the drug Cardiomagnyl.

Green Ion Selective Electrode Potentiometric Application for the Determination of Cinchocaine Hydrochloride in Presence of Its Degradation Products and Betamethasone Valerate: A Comparative Study of Liquid and Solid Inner Contact Ion-Selective Electrode Membranes

The sustainable and green chemistry principles enable scientists to protect and benefit the economy, people and the planet by finding creative and innovative ways to reduce waste, conserve energy, and discover replacements for hazardous substances. In this work, an environmentally friendly ion selective electrode (ISE) potentiometric method was developed for the determination of cinchocaine hydrochloride (CIN) in presence of its degradation products either in bulk powder or in its combined pharmaceutical formulation with betametahsone valerate. Two novel CIN-selective electrodes were fabricated and evaluated. The fabrication of electrodes was based on sodium tetrakis [3,5-bis (trifluoromethyl)phenyl]borate as a cationic exchanger in a PVC matrix with 2-nitrophenyl octyl ether (2-NPOE) as a plasticizer and using 2-hydroxy propyl-β-cyclodextrin (2-HP β-CD) as an ionophore. A comparative study was conducted using two designed CIN-selective electrodes; a conventional liquid inner contact, sensor 1, and a glassy carbon solid contact electrode, sensor 2. Sensor 1 has a linear dynamic range of 3.0 × 10−5 mol L−1 to 1.0 × 10−2 mol L−1, with a Nernstian slope of 54.89 mV/decade and a detection limit of 5.01 × 10−6 mol/L. Sensor 2 shows linearity over the concentration range of 1.0 × 10−5 mol L−1 to 1.0 × 10−2 mol L−1, with a Nernstian slope of 57.01 mV/decade and a limit of detection of 2.51 × 10−6 mol L−1 which is much improved as a result of diminishing ion fluxes in this solid contact ion-selective electrode. The present electrodes show clear selectivity for CIN from several inorganic, structurally related organic molecules, sugars, co-formulated drug, some common drug excipients and its degradation products. The results obtained by the proposed sensors were statistically analyzed and compared with those obtained by official method. No significant difference for either accuracy or precision was observed.

Semifluorinated Polymers as Ion‐selective Electrode Membrane Matrixes

AbstractMost commercially available fluorous polymers are ill suited for the fabrication of ion‐selective electrode (ISE) membranes. Therefore, we synthesized semifluorinated polymers for this purpose. Ionophore‐free ion‐exchanger electrodes made with these polymers show a selectivity range (≈14 orders of magnitude) that is nearly as wide as found previously for liquid fluorous ion‐exchanger electrodes. These polymers were also used to construct ISE membranes doped with fluorophilic silver ionophores. While the resulting ISEs were somewhat less selective than their fluorous counterparts, the semifluorinated polymers offer the advantage that they can be doped both with fluorophilic ionophores and traditional lipophilic ionophores, such as the silver ionophore Cu(II)‐I (o‐xylylenebis[N,N‐diisobutyldithiocarbamate]). We also cross‐linked these polymers, producing very durable membranes that retained broad selectivity ranges. K+ ISEs made with the cross‐linked semifluorinated polymer and the ionophore valinomycin showed selectivities similar to those of PVC membrane ISEs but with a superior thermal stability, the majority of the electrodes still giving a theoretical (Nernstian) response after exposure to a boiling aqueous solution for 10 h.

Ion Aggregation and R3N+-C(R)-H···NR3 Hydrogen Bonding in a Fluorous Phase.

Potentiometric selectivities show that in fluorous ion-selective electrode membranes the tetrabutylammonium ion binds to fluorophilic proton ionophores. For the ionophore bis[3-(perfluorooctyl)propyl](2,2,2-trifluoroethyl)amine, this type of interaction is confirmed by the effect of the ionophore on the ionic conductivity of perfluoro(perhydrophenanthrene) solutions of a fluorophilic NBu4+ salt. In this system, ion pairs, triple ions, and higher ionic aggregates dominate over single ions, and the ionophore increases the conductivity by favoring the formation of ion aggregates with a net charge. These observations are consistent with the formation of R3N+-C(R)-H···NR3 type hydrogen bonds between the nitrogen atom of the ionophore and the hydrogen atoms in the α position to the positively charged quaternary ammonium center of NBu4+. Similar interactions were observed in a number of crystalline phases. To date, observations of C-H···N type hydrogen bonds in liquid phases have been very few, and solution-phase N+-C-H···N type hydrogen bonds have not been reported previously. Interestingly, no interactions between NBu4+ and the more basic ionophore tridodecylamine were observed in conventional plasticized poly(vinyl chloride) membranes doped with the ionophore tridodecylamine, emphasizing the uniquely low polarity of fluorous phases.

New bis(azobenzocrown)s with dodecylmethylmalonyl linkers as ionophores for sodium selective potentiometric sensors.

Novel biscrowns 1 and 2 were synthesized from 13-membered azobenzocrown ethers containing bromoalkylenoxy chains in para position relative to the azo group. The synthesized diester molecules are dodecylmethylmalonic acid derivatives differing by the linker length. The synthesized compounds have the potential of being used as sodium ionophores in ion-selective electrodes. They were characterized and used as ionophores in classic and miniature, solid contact (screen-printed and glassy carbon) membrane ion-selective electrodes. Compound 3, a similar monoester derivative of 13-membered azobenzocrown, was synthesized and used in membrane electrodes for comparison. Lipophilicity of new ionophores was determined by TLC. Lipophilicity of bis(azobenzocrown)s was found to be within the range of logPTLC = 12–13. It was observed that the particularly important selectivity coefficients logK Na,K determined for new electrodes, being logK Na,K = −2.5 and −2.6 (SSM, 0.1 M), are better than those of the electrodes featuring seven out of the nine commercially available sodium ionophores. It was concluded that the ionophore 1 creates, in acetone, with sodium iodide, complex of 1:1 stoichiometry (sandwich complex) with stability constant (logK) ca. 3.0.

Lowering Detection Limits Toward Target Ions Using Quasi-Symmetric Polymeric Ion-Selective Membranes Combined with Amperometric Measurements.

An amperometric method is reported that compensates for the interference from marginally discriminated interfering ions when using traditional polymeric ion-selective membrane (ISM) electrodes. The concept involves utilizing two ISMs in a three-compartment electrochemical cell configuration. The two ISMs are identical in composition except for the addition of an ionophore to one of the membranes. Initially, all three compartments contain the same concentration of interfering ion and the membrane does not contain primary ions. Reference electrodes are placed into each of the two outer compartments. At this point, there is no potential difference between the two reference electrodes. We show experimentally and theoretically that, when the concentration of an interfering species is increased in the sample compartment, the phase-boundary potentials of both sample solution|ISMs change similarly. However, when the primary ion is added to the sample, an asymmetry will emerge, and the membrane with the ionophore will exhibit a larger phase-boundary potential change. At low concentrations, the difference in membrane potentials can be too small for reliable potentiometric detection. Current, which can be routinely measured on pA levels, can be used instead to detect the small primary ion concentration changes with a significant lowering of detection limits. The theory of this method is described by Nernst-Planck-Poisson finite element simulations, and both amperometric and potentiometric experimental verification is demonstrated using ammonium ISM. It is shown that amperometric measurements enable 200 nM ammonium to be detected in the presence of 0.1 mM of potassium, detection capability that is not possible via conventional potentiometry.

Amitriptyline-molybdovanadate/-molybdotungstate based ion-selective membrane electrodes for determination of amitriptyline in pharmaceutical formulations and water samples

Poly (vinyl chloride) membrane electrodes for the determination of amitriptyline hydrochloride were fabricated based on the use of amitriptyline-molybdovanadate and amitriptyline-molybdotungstate as electroactive materials and dioctylphthalate as the plasticizing agent. The effect of membrane composition on the electrode response was studied. The membrane electrodes containing amitriptyline-molybdovanadate (electrode A) and amitriptyline-molybdotungstate (electrode B) showed a fast and stable response over the amitriptyline hydrochloride concentration range 1.0×10−4–1.0×10−2molL−1. Under the optimum conditions, the slope of the calibration curve, and detection limits were found to be −36.2mV/decade; −40.81mV/decade and 6.87×10−5; 6.73×10−5molL−1, for electrodes A and B, respectively. The life span of both the electrodes was found to be more than 2months. The isothermal coefficient of electrodes A and B amounted to 0.00070V/°C and 0.00068V/°C, respectively. Both the electrodes were successfully applied to the determination of amitriptyline hydrochloride in tablets and water samples by direct potentiometric method.

Synthesis, characterization, electrical and dielectrical studies of Polypyrrole-Sn(IV)arsenotungstate nanocomposite ion-exchange membrane: Its selectivity as Ba(II)

Polypyrrole-Sn(IV)arsenotungstate (Ppy-SnAT) nanocomposite cation exchanger membrane was prepared by solution casting method of Polypyrrole in the presence of Sn(II)arsenotungstate gel and polyvinyl chloride (PVC) as a binder. The formation of Polypyrrole-Sn(IV)arsenotungstate nanocomposite cation exchanger membrane was characterized by Fourier Transform Infra-Red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX). The membrane having a composition of 4.5:1 (composite:PVC) shows best results for water content, porosity, thickness and swelling. Our studies show that the present ion selective membrane electrode is selective for Ba(II) metal, having detection limit (1×10−8M to 1×10−1M), response time (35s) and working pH range (3–5). The selectivity coefficient values for interfering ions indicate good selectivity for Ba(II) over interfering cations. The analytical utility of this electrode was established by employing it as an indicator electrode in potentiometric titration. The dielectrical constants (ε′, ε″), dielectric loss (tanδ) and AC conductivity (σac) were studied as a function of frequency.

Activity Coefficient Modeling of Ionic Liquids in Water Based on Ion Selective Electrode Potential Measurements

Two ion selective membrane electrodes were prepared based on the ionic liquids [BMIm]Br and [BMIm]BF4 as ion exchangers in a plasticized PVC matrix. These electrodes exhibit fast, Nernstian responses over a wide concentration range. The selectivity coefficient, detection limit, and calibration slope were determined for the electrodes. The proposed sensors were also utilized to obtain the mean activity coefficients of the studied ionic liquids in water using potentiometry. The data were correlated by the Pitzer and extended Debye–Huckel models.

Simple, Robust, and Plasticizer-Free Iodide-Selective Sensor Based on Copolymerized Triazole-Based Ionic Liquid.

Novel solid-contact iodide-selective electrodes based on covalently attached 1,2,3 triazole ionic liquid (IL) were prepared and investigated in this study. Triazole-based IL moieties were synthesized using click chemistry and were further copolymerized with lauryl methacrylate via a simple one-step free radical polymerization to produce a "self-plasticized" copolymer. The mechanical properties of the copolymer are suitable for the fabrication of plasticizer-free ion-selective membrane electrodes. We demonstrate that covalently attached IL moieties provide adequate functionality to the ion-selective membrane, thus achieving a very simple, one-component sensing membrane. We also demonstrate that the presence of iodide as the counterion in the triazole moiety has direct influence on the membrane's functionality. Potentiometric experiments revealed that each electrode displays high selectivity toward iodide anions over a number of inorganic anions. Moreover, the inherent presence of the iodide in the membrane reduces the need for conditioning. The nonconditioned electrodes show strikingly similar response characteristics compared to the conditioned ones. The electrodes exhibited a near Nernstian behavior with a slope of -56.1 mV per decade across a large concentration range with lower detection limits found at approximately 6.3 × 10(-8) M or 8 ppb. These all-solid-state sensors were utilized for the selective potentiometric determination of iodide ions in artificial urine samples in the nanomolar concentration range.

(Invited) Ionophore-Doped Ion-Selective Electrode Membranes

Ion-selective electrodes with ionophore-doped sensing membranes are are highly sensitive and selective analytical tools that offer a variety of advantages, such as simplicity of measurement, high analysis throughput, rapid detection, and low cost of analysis. While such sensors are used in clinical laboratories for billions of measurements every year, applications in biomedical sciences, the food industry, and environmental monitoring are hindered by biofouling and the frequent need for recalibration. With prolonged exposure to biological samples, solid contact polymeric-membrane ISEs exhibit a breakdown of selectivity and response due to biofouling and changes in the phase boundary potential at the interface of the ion-selective membrane and the underlying electron conductor. Therefore, frequent recalibrations are needed for many clinical and biological applications. This talk will discuss experimental techniques such as impedance spectroscopy and hydrodynamic methods to characterize sensor aging, and it will address the use of hydrophobic redox buffers incorporated into the sensing membranes to stabilize the phase boundary potential at the interface to the underlying electron conductor. These redox buffers permit a high electrode-to-electrode reproducibility of the emf response, which is needed for the development of ion-selective potentiometric devices that can be used in a calibration-free manner [1]. [1] Calibration-Free Ionophore-Based Ion-Selective Electrodes With a Co(II)/Co(III) Redox Couple-Based Solid Contact, Zou, X. U.; Zhen, X. V.; Cheong, J. H.; Bühlmann, P. Anal. Chem., 2014, 86, 8687–8692.

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.