New room temperature ionic liquids with interesting ecotoxicological and antimicrobial properties.

A new set of room temperature ionic liquids (RTIL), tetrabutylammonium (TBA) salts: formate, acetate, propionate, butyrate, benzoate, nitrobenzoate, cinnamate, salicylate, sulfanilate, linoleate, and oleate, were prepared by neutralization of tetrabutylammonium hydroxide (TBA OH) and the corresponding acid. The compounds showed interesting chemical and biological properties. They are soluble in water and organic solvents producing conducting solutions and are effective against certain Gram-negative as well as Gram-positive bacteria. Notably, they affected some proteins such as bovine serum albumin (BSA) and catalase (CAT) as inferred by following the fluorescence emission spectra.

Improving the detection limits of antispasmodic drugs electrodes by using modified membrane sensors with inner solid contact.

Three coated wire electrodes (CWEs) for the antispasmodic drugs; dicyclomine (Dc), mebeverine (Mv) and drotaverine (Dv) hydrochlorides were developed. Each electrode based on ion-associate of a heteropoly anion with the drug cation incorporated in membrane sensor modified with graphite and deposited on silver internal solid contact. The influence of addition of graphite to the membranes and the type of the internal solid contact on the potentiometric responses of the electrodes was investigated. The characteristics of the new electrodes were compared to the characteristics of previously reported traditional liquid inner contact electrodes of the same drugs. The lower detection limits of the proposed electrodes were somewhat better than those observed with the corresponding liquid contact ISEs and reached (1.2-2.0)x10(-7)M. The potentiometric selectivity of the CWEs revealed a significant improvement and much faster response times compared to the liquid contact ISEs. The practical utility of each electrode has been demonstrated by using it successfully in potentiometric determination of its respective drug in pharmaceutical preparations both in batch and flow injection conditions. Each electrode was also used as an indicator electrode in the potentiometric titration of the drug against standard silicotungstic acid and in potentiometric determination of the drug concentration in urine samples.

Potentiometric flow injection analysis of mebeverine hydrochloride in serum and urine.

Four PVC membrane electrodes for the determination of mebeverine hydrochloride (MvCl) were fabricated and fully characterized in terms of composition, life span, usable pH range, working concentration range and temperature. The membranes of these electrodes consist of mebeverinium-silicotungstate (Mv-ST), silicomolybdate (Mv-SM), phosphotungstate (Mv-PT), or phosphomolybdate (Mv-PM) ion-associations dispersed in PVC matrix with dibutyl phthalate plasticizer. The electrodes showed near-Nernstian response over the concentration range of 4.0 x 10(-6) to 1.0 x 10(-2)M MvCl and were applied to the potentiometric determination of mebeverinium ion in pharmaceutical preparations, serum and urine in steady state and flow injection (FI) conditions with average recoveries of 96.4-102 % and relative standard deviations of 0.132-1.86%. The electrodes exhibit good selectivity for MvCl with respect to a large number of inorganic cations, organic cations, sugars and amino acids. The sensitivities of these electrodes are high enough to measure as low as 1.86 microg/ml of MvCl which permit the determination of the Ksp values of the ion-associates used. The proposed potentiometric methods offer the advantages of simplicity, accuracy, automation feasibility and applicability to turbid and colored sample solutions.

A new approach for decreasing the detection limit for a ketamine(I) ion-selective electrode.

Our endeavors of lowering the detection limit for a ketamine(I) ion-selective electrode were described. The paper stresses the electrode which showed best results for determination of ketamine ion. The present electrode incorporates ketamine-phosphomolybdate (KT-PM) as ion-exchanger combined with the lipophilic anionic additive (Na-TPB) dissolved in dibutyl phthalate (DBP) as a plasticizer. The characteristics of the electrode were elaborately measured and its performance was tested in various samples and urine. It has favorable features as it provides measurements of the potential with a near-Nernstian slope of 56.6±0.3mV/decade over the concentration range of 1.5×10(-6)-1.0×10(-2)M over the pH range 3.0-6.8 in a short response time (7s). Importantly, it has a low detection limit of 1.2×10(-7)M and its life-span is 22days. Moreover, it displayed notable selectivity for ketamine ion over other species such as inorganic and organic cations and different excipients which may be present in pharmaceutical preparations. The sensor was applied for determination of KT ions in urine and pharmaceutical preparations using potentiometric determination, standard addition and the calibration curve methods. The standard deviation computed on the results indicated excellent repeatability of the measurements. Overall, it showed satisfactory results with excellent percentage recovery comparable to and sometimes better than those obtained by other routine methods for the assay.

Chemically modified carbon paste electrode for the potentiometric determination of dicylomine hydrochloride in batch and in FIA conditions.

A carbon-paste electrode for dicyclomine hydrochloride (DcCl) was prepared and fully characterized in terms of composition, life span, usable pH range and temperature. The electrode was applied to the potentiometric determination of dicylominium ion in its pure state and in pharmaceutical preparations in batch and flow injection conditions and in biological fluids using standard additions method. The electrode is based on a mixture of two ion-exchangers, namely, dicyclominium-phosphomolybdate and dicylominium-tetraphenylborate, dissolved in dioctyl phthalate as pasting liquid. The modified electrode showed a near-Nernstian slope of 58 +/- 2 mV over the concentration range of 1.2 x 10(-5)-1.6 x 10(-2) M with an average recovery of 97-102% and a RSD of 0.090-1.00. The electrode exhibits good selectivity for DcCl with respect to a large number of inorganic cations, sugars, amino acids and organic substances of biological fluids. Potentiometric titrations of DcCl with several titrants have been monitored using this modified carbon paste electrode as an end-point indicator electrode.

Determination of pethidine hydrochloride using potentiometric coated graphite and carbon paste electrodes.

A new approach for lowering the detection limit of a pethidine ion-selective electrode is presented. A coated graphite (CGE) and carbon paste (CPE) electrodes for pethidine ions based on pethidine-phosphotungstate (PD-PT) as ion-pair complex are described. The sensors exhibit a Nernstian slope of 58.1 and 54.2 mVdecade(-1) for pethidine ion over a wide concentration range from 2.6 × 10(-7) to 1.0 × 10(-2) M and 2.1 × 10(-6) to 1.0 × 10(-2) M with a detection limit of 1.8 × 10(-7) M and 7.3 × 10(-7) M for pethidine coated graphite (PD-CGE) and pethidine carbon paste electrode (PD-CPE), respectively. These sensors exhibited a fast response time (about 5-8 s) and good stability. The standard electrode potentials, E(o) , were determined at different temperatures and used to calculate the isothermal temperature coefficient (dE(o) /dT) of the PD-CGE and PD-CPE, which was 0.0062 and 0.0071 V/ °C, respectively. Selectivity coefficients, determined by matched potential method (MPM) and separate solution method (SSM), showed high selectivity for pethidine hydrochloride (PDCl) over a large number of inorganic cations, organic cations, sugars, urine components, and some common drug excipients. The sensors were applied for determination of PDCl in ampoule and in spiked urine samples using potentiometric determination, standard addition and the calibration curve methods. The results obtained were satisfactory with excellent percentage recovery comparable and sometimes better than those obtained by other routine methods for the assay.

Development of novel potentiometric sensors for determination of tartrazine dye concentration in foodstuff products.

Tartrazine dye Na(3)TZ in foodstuff products was determined by a new modified carbon paste electrode, encoded sensor A, and a coated silver wire electrode, encoded sensor B, based on tartrazine TZ- cetryltrimethyl ammoniumbromide CTAB as a chemical modifier TZ-CTA. The electrodes exhibit the following characteristics listed respectively: a Nernstian slope of 17.9±0.5 and 19.4±0.2 mV/decade for tartrazine ion over a wide concentration range from 4.3×10(-7) to 1.0×10(-2) and 1.1×10(-7) to 1.0×10(-2) M. The lower detection limits: 3.2×10(-7) and 5.5×10(-8) M. Short response time (5-8 s) over the pH range 3.8-7.7 and 4.2-8.1. The proposed sensors display significantly high selectivity for TZ ion over a wide variety of sugars, some anions, common organic, inorganic compounds and additives. The developed electrodes were applied to the potentiometric determination of tartrazine ion in different kinds of foodstuffs: solid jelly (strawberry and custard) powder samples and soft drink (orange) samples with satisfactory results.

A comparative study of solid and liquid inner contact benzalkonium chloride ion-selective electrode membranes.

A comparative study was made between two designs of benzalkonium ion (Bz)-selective electrodes: a silver-coated (solid contact) called electrode A and a PVC membrane (liquid inner contact) called electrode B based on benzalkonium-phosphomolybdate (Bz-PM) as ion-exchanger complex. Electrode A has a linear dynamic range from 2.0×10(-8) to 1.0×10(-2) mol L(-1), with a Nernstian slope of 60±0.3 mV/decade and a detection limit of 2.0×10(-8) mol L(-1). Electrode B shows linearity over the concentration range from 2.0×10(-7) to 1.0×10(-2) mol L(-1), with a Nernstian slope of 55±1.2 mV/decade and a limit of detection of 1.5×10(-7) mol L(-1). Electrode A showed better performance than electrode B. The detection limit of benzalkonium chloride (BzCl) was effectively improved by a solid contact ion-selective electrode (SC-ISE), rather than the traditional liquid inner contact electrode that gives lower detection limits because of diminished ion fluxes. The present electrodes show clear discrimination of BzCl from several inorganic, organic ions, sugars and some common drug excipients. The sensors were applied efficiently for determination of BzCl in its pharmaceutical preparations (eye, ear and nasal drops) using standard addition and the calibration curve methods.

A mercury(II) selective sensor based on N,N'-bis(salicylaldehyde)-phenylenediamine as neutral carrier for potentiometric analysis in water samples.

Mercuric ions in water samples were determined by a new modified carbon paste electrode based on N,N'-bis(salicylaldehyde)-phenylenediamine (salophen) as a chemical modifier. The construction, performance, and applications of mercury carbon paste electrode are described. The electrode displays a linear log[Hg(2+)] versus EMF response over a wide concentration range of 3.2 x 10(-7) to 3.2 x 10(-4) with Nernstian slope of 58.8+/-0.3 mV/decade with limit of detection 1.5 x 10(-7) over the pH range 3.8-7.8; the presence of the complex Hg(OH)(+) ion explains the slope of the response curve. The proposed sensor shows a reasonable discrimination ability towards Hg(II) in comparison to some alkali, alkaline earth transition and heavy metal ions. The modified electrode was applied as indicator electrode in potentiometric titration and successfully used to determine mercury(II) in water samples with satisfactory results.

Enhanced sensitivity for Cu(II) by a salicylidine-functionalized polysiloxane carbon paste electrode.

A new approach for decreasing the detection limit for a copper(II) ion-selective electrode (ISE) is presented. The ISE is designed using salicylidine-functionalized polysiloxane in carbon paste. This work describes the attempts to develop the electrode and measurements of its characteristics. The new type of renewable three-dimensional chemically modified electrode could be used in a pH range of 2.3-5.4, and its detection limit is 2.7 x 10(-8)mol L(-1) (1.2 microg L(-1)). This sensor exhibits a good Nernstian slope of 29.4+/-0.5 mV/decade in a wide linear concentration range of 2.3 x 10(-7) to 1.0 x 10(-3)mol L(-1) of Cu(II). It has a short response time (approximately 8s) and noticeably high selectivity over other Cu(II) selective electrodes. Finally, it was satisfactorily used as an indicator electrode in complexometric titration with EDTA and determination of copper(II) in miscellaneous samples such as urine and various water samples.