Rasha M. El-Nashar

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.

Salbutamol plastic membrane electrodes based onindividual and mixed ion-exchangers of salbutamolium phosphotungstate andphosphomolybdate

Salbutamol (Sl), also known as albuterol, selective PVC membranes based on ion associates of salbutamolium phosphotungstate (Sl-PTA), salbutamolium phosphomolybdate (Sl-PMA) or a mixture of both (Sl-PTA/PMA) were prepared. The electrodes displayed a linear response over the concentration range 6.3 × 10−6–1.0 × 10−1 mol dm−3 salbutamol sulfate (Sl2SO4). The working pH ranges of the above electrodes were 2.5–11.0, 3.0–11.0 and 2.5–10.5 and their isothermal temperature coefficients were 0.00095, 0.00105 and 0.00136 V °C−1, respectively. The electrodes showed good selectivity to salbutamolium ion with respect to many inorganic cations, sugars and amino acids. The standard additions method was used to determine Sl2SO4 in pure solutions and pharmaceutical preparations with high accuracy and precision.

Construction and performance characteristics of new ion selective electrodes based on carbon nanotubes for determination of meclofenoxate hydrochloride

This work offers construction and comparative evaluation the performance characteristics of conventional polymer (I), carbon paste (II) and carbon nanotubes chemically modified carbon paste ion selective electrodes (III) for meclofenoxate hydrochloride are described. These electrodes depend mainly on the incorporation of the ion pair of meclofenoxate hydrochloride with phosphomolybdic acid (PMA) or phosphotungestic acid (PTA). They showed near Nernestian responses over usable concentration range 1.0 × 10(-5) to 1.0 × 10(-2)M with slopes in the range 55.15-59.74 mV(concentrationdecade)(-1). These developed electrodes were fully characterized in terms of their composition, response time, working concentration range, life span, usable pH and temperature range. The electrodes showed a very good selectivity for Meclo with respect to a large number of inorganic cations, sugars and in the presence of the degradation product of the drug (p-chloro phenoxy acetic acid). The standard additions method was applied to the determination of MecloCl in pure solution, pharmaceutical preparations and biological samples. Dissolution testing was also applied using the proposed sensors.

Determination of the design space of the HPLC analysis of water-soluble vitamins.

Analysis of water-soluble vitamins has been tremendously approached through the last decades. A multitude of HPLC methods have been reported with a variety of advantages/shortcomings, yet, the design space of HPLC analysis of these vitamins was not defined in any of these reports. As per the food and drug administration (FDA), implementing the quality by design approach for the analysis of commercially available mixtures is hypothesized to enhance the pharmaceutical industry via facilitating the process of analytical method development and approval. This work illustrates a multifactorial optimization of three measured plus seven calculated influential HPLC parameters on the analysis of a mixture containing seven common water-soluble vitamins (B1, B2, B6, B12, C, PABA, and PP). These three measured parameters are gradient time, temperature, and ternary eluent composition (B1/B2) and the seven calculated parameters are flow rate, column length, column internal diameter, dwell volume, extracolumn volume, %B (start), and %B (end). The design is based on 12 experiments in which, examining of the multifactorial effects of these 3 + 7 parameters on the critical resolution and selectivity, was carried out by systematical variation of all these parameters simultaneously. The 12 basic runs were based on two different gradient time each at two different temperatures, repeated at three different ternary eluent compositions (methanol or acetonitrile or a mixture of both). Multidimensional robust regions of high critical R(s) were defined and graphically verified. The optimum method was selected based on the best resolution separation in the shortest run time for a synthetic mixture, followed by application on two pharmaceutical preparations available in the market. The predicted retention times of all peaks were found to be in good match with the virtual ones. In conclusion, the presented report offers an accurate determination of the design space for critical resolution in the analysis of water-soluble vitamins by HPLC, which would help the regulatory authorities to judge the validity of presented analytical methods for approval.

Etilefrine Plastic Membrane Electrodes Based on Individual and Mixed Ion-exchangers of Etilefrinium Phosphotungstate and Tetraphenylborate.

Abstract Etilefrine hydrochloride (EfCl) selective PVC membrane electrodes based on Etilefrinium phosphotungstate (I), Etilefrinium tetraphenylborate (II) and a mixture of both (III) were prepared, The electrodes exhibited near Nernstian response over the concentration ranges 5.0 × 10−6 - 1.0 × 10−1, 6.3 × 10−6 - 1.0 × 10−1 and 6.3 × 10−5 - 1.0 × 10−1 M EfCl for electrodes I, II and III, respectively. The working pH ranges of electrodes I, II and III were 10 - 8.0, 10 - 7.5 and 10 - 7.5 and their isothermal coefficients were 0.00150, 0.00088 and 0.00072 V/°C, respectively. The electrodes showed good selectivity to EfCl with respect to many inorganic cations, sugars and amino acids. The standard additions method was used to determine EfCl in pure solutions and in pharmaceutical preparations.

Potentiometric flow injection determination of salbutamol

ABSTRACT Potentiometric detection of salbutamol sulphate Sl2SO4 using electrodes containing its ion-exchangers with phosphotungstic; phosphomolybdic acid or a mixture of both was applied in flow injection systems in the Nernastian range of the electrodes response. The selectivity of these electrodes towards different cations was studied in comparison to that obtained in batch conditions. The method was then used to determine the drug in its pharmaceutical preparations.

Flow Injection Potentiometric Determination of Dothiepin Hydrochloride

Abstract New plastic membrane electrodes for dothiepin hydrochloride (DpCl) based on dothiepin phosphotungstate (Dp‐PTA), dothiepin phosphomolybdate (Dp‐PMA), and a mixture of both (Dp‐PTA/PMA) were prepared. The electrodes were fully characterized in terms of their composition, life span, pH, and temperature, and then were applied to the potentiometric determination of the dothiepinium ion in its pure state and pharmaceutical preparations in batch and flow injection conditions. The selectivity of the electrodes toward many inorganic cations, sugars, and amino acids was also tested.

Flow-injection potentiometric and conductometric determination of papaverine hydrochloride in the parent substance and a related pharmaceutical preparation

Papaverine (Pap) ion-selective plastic membrane electrodes based on ion associates of papaverine with phosphotungstic acid (Pap-PTA) and phosphomolybdic acid (Pap-PMA) were prepared and fully characterized in terms of membrane composition, life span, pH, and temperature. The proposed electrodes were applied to potentiometeric determination of papaverine in the parent substance and a related pharmaceutical preparation under batch and flow-injection analysis conditions. In addition, conductometric titrations were used for the assay of papaverine in the parent substance and the related pharmaceutical preparation. The selectivity of electrodes with respect to a large number of foreign inorganic cations, amino acids, and sugars was tested. The solubility product of the ion associate and the rate constant of the precipitation reaction leading to the ion associate formation were determined conductometrically.

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

Abstract 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.

Enantiomeric Separation of Underivatized Amino Acids: Predictability of Chiral Recognition on Ristocetin A Chiral Stationary Phase

The present work aimed to investigate the predictability of the chromatographic behavior for the separation of underivatized amino acids on ristocetin A, known as Chirobiotic R, using a DryLab high-performance liquid chromatography (HPLC) method development software, which is typically used to predict the effect of changing various chromatographic parameters on resolution in the reversed phase mode. After implementing the basic runs, and judging the predictability via the computed resolution map, it can be deduced that the chiral recognition mechanisms tend towards a hydrophilic interaction chromatography rather than the reversed phase mode, which limits the ability of DryLab software to predict separations on Chirobiotic R.