Plastic Membrane Ion-selective Electrode Research Articles

Dissolution testing and potentiometric determination of famciclovir in pure, dosage forms and biological fluids

The performance characteristics of two new plastic membrane ion selective electrodes (ISEs) used for the determination of famciclovir (Fcv) based on the ion associate of Fcv with phosphotungstic acid (PTA) or phosphomolybdic acid (PMA) are described. Different experimental conditions as type of plasticizer to be incorporated in the membrane, life span, effect of soaking, pH, temperature, and interferences were studied. Both electrodes showed similar performance under these conditions, exhibiting Nernstian slopes of S (Fcv-PTA)=58.60±0.84mV/decade and S (Fcv-PMA)=58.77±0.68mV/decade within a usable concentration range of 10−5–10−2 [Fcv/M] at 298/K. Famciclovir was assayed potentiometrically in its pure solution, pharmaceutical preparations and biological fluids (urine and plasma) using proposed electrodes under batch and flow injection analysis (FIA) conditions with a recovery % ranging between 96.76% and 102.83% having RSD of 0.66%–1.81%. The electrodes were also successfully applied in the determination of the dissolution profile of Fcv tablets and the results came in agreement with the validated results of the HPLC method obtained from the quality control unit of the company producing the tablets.

Single interface flow system with potentiometric detection for the determination of nitrate in water and vegetables

In this work a single interface flow system (SIFA) with potentiometric detection was for the first time implemented and applied to the determination of nitrate in waters and plant extracts. The analytical potential of the SIFA system was exploited not only to transport the sample towards detection but also to carry out, in a reproducible and automated way, the tasks associated with sample pre-treatment, namely ionic strength, pH adjustment and interfering species suppression. The advantageous aspects of combining a SIFA system with potentiometry with enhanced simplicity, ease of implementation and automation were further discussed and emphasised. The obtained results showed relative deviations lower than 5%, for both types of samples, with sampling rates of about 40 h −1. In addition, an innovative and straightforward process for constructing plastic membrane ion selective electrodes with a tubular configuration able to be coupled to flow-based analytical systems is also proposed. The developed approach, consisting of assembling the electrode inside a flow tubing connector is very simple to implement, robust, particularly adequate to be combined with flow methodologies and maintains all dynamic and analytical characteristics exhibited by previous assembling processes.

Flow Injection Analysis with Tubular Membrane Ion‐Selective Electrode and Coated Wires for Buspirone Hydrochloride

New Plastic membrane ion-selective electrode for buspirone hydrochloride based on buspironium tetraphenylborate was prepared. The electrode exhibited mean slope of calibration graph of 58.4 mV per decade of BusCl concentration at 25 degrees C. The electrode can be used within the concentration range 6.3 x 10(-5) - 10(-2) M BusCl at a pH range of 2.5-7.0. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal temperature coefficient of the electrode, amounting to 0.00056 V degrees C(-1). The electrode showed a very good selectivity for BusCl with respect to a number of inorganic cations, sugars and amino acids. The electrode was applied to the potentiometric determination of the buspirone ion and its pharmaceutical preparation under batch and flow injection conditions. Also, buspirone was determined by conductimetric titrations. Graphite rod, copper and silver coated wire electrodes were prepared and characterized as sensors for the drug under investigation.

Development of novel plastic membrane Ion-selective electrode for metformin hydrochloride

A new plastic membrane ion-selective electrode for determination of metformin hydrochloride has been prepared, after forming the ion pair of metformin hydrochloride with sodium tetraphenylborate. Dioctyl phthalate and sodium tetraphenylborate were used as plasticizer and counter ion respectively. The electrode exhibited a linear potential response in the concentration range 1 × 10-5 M–1 × 10-1 M with slope of 42.0±0.82 mv per decade. The electrode has a rapid response time (45 s), shorter conditioning time (2 h) and a lower limit of detection (1 × 10-5 M). The electrode showed high selectivity for metformin hydrochloride with respect to some common ions, excipients and other drugs present as combined dosage formulations. Stability studies of ion-selective membrane were carried out by differential scanning calorimetry. The electrode can successfully be applied for the analysis of metformin hydrochloride in pure solution, pharmaceutical preparations, biological fluid and in presence of its degraded products.

Flow Injection Analysis With Trimetazidine Dihydrochloride Ion-Selective Electrode

New Plastic membrane ion-selective electrode for trimetazidine dihydrochloride based on trimetazidinium-tetraphenylborate was prepared. The electrode exhibited mean calibration graph slope of 29.5 mV per decade of (TrimCl2) concentration at 25°C. The electrode can be used within the concentration range 3.2×10-5-10-2 M (TrimCl2) at pH ranges of 1.5-3.8 and 4.5-7.5. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode, which was (0.00088 V°C-1). The electrode showed a very good selectivity for (TrimCl2) with respect to a number of inorganic cations, sugars and amino acids. The electrode was applied to the potentiometric determination of the trimetazidine ion and its pharmaceutical preparation under batch and flow injection conditions. Graphite coated wire was prepared and characterized as sensor for the drug under investigation. Also, trimetazidine was determined by conductimetric titrations.

Reproterol plastic membrane ion-selective electrodes based on its individual and mixed ion-exchangers with phosphotungstic and/or phosphomolybdic acids

Reproterol hydrochloride (RpCl), selective PVC membranes based on ion associates of reproterolium-phosphotungstate (Rp-PTA); reproterolium-phospho-molybdate (Rp-PMA) or a mixture of both (Rp-PTA/PMA) were prepared. The electrodes displayed a linear response over the concentration range of 6.3×10 −6–1.0×10 −1 mol dm −3 RpCl. The working pH ranges of the above electrodes were 2.5–9.0, 2.5–8.5 and 2.0–9.0 and their isothermal temperature coefficients were 0.00014, 0.00090 and 0.00103 V/°C, respectively. The electrodes showed good selectivity to the reproterolium ion with respect to many inorganic cations, sugars and amino acids. The standard additions and potentiometric titration methods were used to determine RpCl in pure solutions and in its pharmaceutical preparations with high accuracy and precision.

Plastic membrane electrode for selective determination of diclofenac (voltaren) in pharmaceutical preparations

A novel plastic membrane ion-selective electrode for determining the diclofenac anion is described. The sensing membrane of the electrode consists of diclofenac-nickel(II) bathophenanthroline as an ion-exchanger site in a poly(vinyl chloride) matrix plasticized with o–nitrophenyl phenyl ether. In borate buffer solutions of pH 8–12, the electrode exhibits a fast, stable and linear response for 1 × 10–2–5 × 10–5 mol dm–3 diclofenac with an anionic slope of 55.1 ± 0.2 mV decade–1 at 25 °C. Potentiometric selectivity measurements revealed negligible interferences from 14 different anions including aromatic and aliphatic carboxylic acid salts. The electrode displays useful analytical characteristics for the direct determination of diclofenac in various pharmaceutical preparations. Results with an average recovery of 98 ± 0.6% of the nominal value were obtained.

Plastic membrane ion selective electrodes for the determination of some anesthetic compounds

Lignocaine (LC), procaine (PC), and benzocaine (BC) ion selective electrodes based on incorporation of ion pairs of tetraphenylborate anion (TPB) with protonated LC, PC, and BC in plasticized polyvinyl chloride membranes were prepared. The electrodes showed linear responses with Nernstian slopes over the concentration ranges 3.16 × 10 −5–1.25 × 10 −2, 1.99 × 10 −5–1.60 × 10 −2, and 6.31 × 10 −6–1.20 × 10 −2 M of LC, PC, and BC, respectively. The change in pH did not affect the electrode performance within the ranges 2.0–7.6, 2.9–8.1, and 5.5–8.5 for the three electrodes, respectively. The electrodes were very selective for the respective drugs and exhibited very small isothermal coefficients amounting to 0.00099, 0.00083, and 0.00065 V/deg for LC, PC, and BC electrodes, respectively. Potentiometric titrations were successfully applied to determine LC, PC, and BC using standard TPB solution as titrant and the respective electrodes as potentiometric sensors.

Determination of tetracycline and related compounds using plastic membrane ion-selective electrodes

PVC membrane electrodes selective for hydrochlorides of tetracycline (TC), doxycycline (DC) and oxytetracycline (OTC) are prepared. The electrodes show a linear response with Nernstian slope over the range of 1.6 × 10 −5–10 −2 M, 7.9 × 10 −5–1.9 × 10 −3 M, and 6.3 × 10 −5–6.3 × 10 −3 M for TC, DC, and OTC, respectively. The effects of pH of the test solution and time of soaking on the electrodes' performance are studied. The electrodes exhibit good selectivity for the investigated antibiotics with respect to a large number of inorganic cations and organic substances of biological importance. TC, DC, and OTC are determined successfully in pure solutions and in some pharmaceutical preparations using the standard additions method.

Simple determination of ammonium and nitrate ions in activated sludge process waters with plastic-membrane ion selective electrodes.

Determination of ammonium and nitrate ions in activated sludge process waters was examined by using plastic-membrane ammonium- and nitrate-selective electrodes. Magnesium sulfate solution was added to the samples for adjustment of ionic strength. Consequently the sample solutions contained 2.5×10-2 M MgSO4. Results obtained for ammonium ion (NH4+-N, 125 mg/l) were a little higher than those by ion chromatography and coulometric titration method. Results for nitrate ion (NO3--N, 136mg/l) were slightly higher than those by ion chromatography. These results could be attributed to interference by potassium and chloride ions (determined by ion chro-matography) for ammonium- and nitrate-selective electrodes, respectively. Thus, the present method is useful for routine analysis and successfully gives quick results on the effectiveness of nitrofication-denitrofication process.