Surface analysis of new chlorpromazinium plastic membrane electrodes.

New chlorpromazinium (Cp) plastic membrane electrodes of the conventional type were constructed and characterized. They are based on incorporation of Cp-reineckate (CpRn) ion pair, Cp-phosphotungstate (Cp3PT), or Cp-phosphomolybdate (Cp3PM) ion associate into poly(vinyl chloride) membrane. The electrodes exhibited calibration graph slopes of 49.83, 52.87, and 61.30 mV/Cp concentration decade over life spans of 1, 5, and 3 days, respectively. All electrodes proved to be selective for Cp and have been applied to the assay of a pharmaceutical preparation. Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), as well as scanning electron microscopy (SEM) showed that the limitation of the lifetime of the electrodes is attributed to leaching of the ion exchanger from the membrane into the test solution in addition to deformation of the surface.

New conventional coated-wire ion-selective electrodes for flow-injection potentiometric determination of chlordiazepoxide.

New chlordiazepoxide hydrochloride (Ch-Cl) ion-selective electrodes (conventional type) based on ion associates, chlordiazepoxidium-phosphomolybdate (I) and chlordiazepoxidium-phosphotungstate (II), were prepared. The electrodes exhibited mean slopes of calibration graphs of 59.4 mV and 60.8 mV per decade of (Ch-Cl) concentration at 25 degrees C for electrodes (I) and (II), respectively. Both electrodes could be used within the concentration range 3.16 x 10(-6)-1 x 10(-2) M (Ch-Cl) within the pH range 2.0-4.5. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficients of the electrodes, which were 0.00139 and 0.00093 V degrees C(-1) for electrodes (I) and (II), respectively. The electrodes showed a very good selectivity for Ch-Cl with respect to the number of inorganic cations, amino acids and sugars. The electrodes were applied to the potentiometric determination of the chlordiazepoxide ion and its pharmaceutical preparation under batch and flow injection conditions. Also, chlordiazepoxide was determined by conductimetric titrations. Graphite, copper and silver coated wires were prepared and characterized as sensors for the drug under investigation.

Ionization of some derivatives of benzamide, oxamide and malonamide in DMF-water mixture.

The ionization of six compounds of bis-phenolic amides was studied spectrophotochemically in DMF-water mixture. The compounds showed two pK(a) values in the range of 5.97-7.32 for pK(a(1)) and 7.61-8.44 for pK(a(2)). The obtained values of K(a) were normalized using the distribution diagrams of the different species and found to be in the range of 5.81-7.42 for pK(a(1)) and 7.48-8.27 for pK(a2).

Spectrophotometric determination of meclozine HCl and papaverine HCl in their pharmaceutical formulations.

A simple, accurate and highly sensitive spectrophotometric method is proposed for the rapid determination of meclozine and papaverine hydrochlorides using chromotrope 2B (C2B) and chromotrope 2R (C2R). The method consists of extracting the formed ion-associates into chloroform in the case of meclozine HCl and into methylene chloride in case of papaverine HCl. The ion-associates exhibit absorption maxima at 536 and 524 nm for C2B and C2R with meclozine HCl and at 540 and 528 nm with papaverine HCl, respectively. Meclozine can be determined up to 4.0 and 2.6 mg ml(-1), using C2B and C2R, respectively, while papaverine can be determined up to 1.68 and 1.37 mg ml(-1), respectively. The effect of acidity, reagent concentration, time, solvent and stoichiometric ratio of the ion-associates were studied. The molar absorptivity and Sandell sensitivity of the reaction products were calculated. The method was applied to the determination of the drugs in their pure state or pharmaceutical preparations with mean recovery values of 99.63-100.80 and 99.75-100.08% and coefficient of variation 0.945-2.210 and 1.020-1.268 for meclozine HCl and papaverine HCl, respectively.

Conductimetric determination of reproterol HCl and pipazethate HCl and salbutamol sulphate in their pharmaceutical formulations.

A simple and sensitive conductimetric method for the determination of salbutamol sulphate and reproterol and pipazethate hydrochlorides is presented based on their ion associates with phosphotungstic and phosphomolybdic acids. The effect of solvent, molar ratio, reagent concentration and temperature were studied, and the solubility products of the formed ion associates were calculated. The method was applied to the determination of the drugs in their pure state or pharmaceutical preparations with mean recovery values of 99.82-100.54, 99.75-100.12 and 99.95-100.40%, and coefficient of variation 0.28-0.52, 0.16-0.36 and 0.19-0.33 for salbutamol sulphate, reproterol HCl and pipazathate HCl, respectively.

Flow injection potentiometric determination of pipazethate hydrochloride.

New plastic membrane electrodes for pipazethate hydrochloride based on pipazethatium phosphotungstate, pipazethatium phosphomolybdate and a mixture of the two were prepared. The electrodes were fully characterized in terms of composition, life span, pH and temperature and were then applied to the potentiometric determination of the pipazethate ion in its pure state and pharmaceutical preparations under batch and flow injection conditions. The selectivity of the electrodes towards many inorganic cations, sugars and amino acids was also tested.

Potentiometric determination of ephedrine hydrochloride using plastic membrane ion-selective electrode.

A plastic membrane electrode based on phenylephrine-tetraphenylborate ion association shows a Nernstian response to both ephedrinium (Ep+) and silver (Ag+) cations over the concentration ranges 2 x 10(-5)-10(-1) M and 10(-5)-10(-1) M for Ep+ and Ag+, respectively. The performance characteristics of the electrode were investigated. The electrode proved to be an excellent potentiometric sensor for the determination of Ep-hydrochloride in its pure solutions and pharmaceutical preparations using the extrapolation method and potentiometric titration using a standard solution of AgNO3.

Selective membrane electrode potentiometry and spectrophotometry of a photochemical reaction of thioredazine hydrochloride.

A PVC membrane electrode of the coated wire type was prepared which is selective for thioredazine. It showed a Nernstian response over a thioredazine concentration range 6.3 x 10(-6) to 2.5 x 10(-3) M, at 25 degrees C, and was selective, precise, and usable within the pH range 2.1-7.0. The standard electrode potentials, E degrees, were determined at different temperatures and used to calculate the isothermal temperature coefficient of the electrode. The photoreaction occurring in thioredazine solution exposed to daylight did not affect the electrode performance. This reaction was investigated kinetically to determine its rate constant and half-life at different temperatures.

Hydralazine-selective PVC membrane electrode based on hydralazinium tetraphenylborate.

A hydralazine ion-selective PVC membrane electrode based on hydralazinium tetraphenylborate has been prepared with dioctyl phthalate as plasticizer. The electrode showed linear response with a slope factor of 57.5 mV/concentration decade at 20 degrees over the concentration range from 4 x 10(-4) to 10(-1)M hydralazine. The effects, on the electrode performance, of membrane composition, pH of the test solution and the time of soaking were studied. The electrode exhibited good selectivity for hydralazine with respect to a large number of inorganic cations and organic substances of biological importance. The standard-addition method and potentiometric titrations were used to determine hydralazine concentrations in pure solutions and in a pharmaceutical preparation, with satisfactory results.