Omayma Abdel Razak

Utilization of carbon disulphide for the analytical determination of betahistine hydrochloride and captopril in their pharmaceutical preparations

Spectrophotometric, atomic absorption spectrometric and high performance liquid chromatographic (HPLC) procedures have been developed for the determination of betahistine hydrochloride and captopril. The three procedures are based on the reaction of the drugs with carbon disulphide in alkaline medium with the formation of the dithiocarbamate or the trithiocarbonate derivative of betahistine (BHT) and captopril (CAP), respectively, then subsequent chelation with divalent metals. The absorbance measurement of the formed chelates or of the metal moiety of chelates was used as the basis for the spectrophotometric and atomic absorption spectrometric determinations. The formed complexes have been used as pre-column derivatizing procedure for the HPLC determination of the two drugs. The different experimental conditions were optimized. The calibration graphs were linear over the applicable concentration ranges. The proposed procedures were applied successfully for the determination of the two investigated drugs in their tablets dosage form.

Spectrophotometric and HPLC determination of secnidazole in pharmaceutical tablets.

Simple and accurate spectrophotometric and HPLC methods were developed for the determination of secnidazole in tablets dosage form. The first spectrophotometric method depends on the reduction of secnidazole molecule with zinc dust and hydrochloric acid followed by condensation with either p-dimethylaminobenzaldehyde or anisaldehyde to give colored chromogens having absorbance at 494 and 398 nm, respectively. The second method was based on the reaction of the drug with sodium nitroprusside in the presence or absence of hydroxylammonium hydrochloride. The formed colored chromogens were measured at 584 and 508 nm, respectively. The experimental conditions were optimized and Beers law was obeyed over the applicable concentration ranges. The application of HPLC procedures depended on using either a conventional or microbore reverse-phase (C18) column along with mobile phases consisting of water and methanol (30:70), at pH of 3.5. Both techniques were applied successfully for the analysis of secnidazole in tablets form. The results obtained from both procedures were statistically compared using the Students-t and F-variance ratio tests.

Fluorimetric and spectrophotometric determination of ritodrine hydrochloride in bulk and pharmaceutical formulations

Two simple sensitive and accurate methods have been developed for the determination of ritodrine hydrochloride in bulk and pharmaceutical preparations. The first method involves the direct measurement of the native fluorescence of the drug in the concentration range 4-9 microg ml(-1), the second method is based on the oxidation of ritodrine HCl with cerium(IV) followed either by spectrophotometric or fluorimetric measurement in the concentration ranges 0.5-1.0 and 0.05-0.1 microg ml(-1), respectively. The interference of various formulation excipients was examined. The reliability of the proposed methods was checked at three different concentrations; the standard deviation varied from 2.7 x 10(-3)-0.109. The described methods have been applied to the determination of ritodrine HCl in tablets and ampoules. The assay results showed insignificant difference with those of the official USP 23 HPLC method.

Polarographic determination of phenytoin and benzophenone (as impurity) in pharmaceutical preparations

A differential pulse polarographic method is described for detection and trace determination of benzophenone (the main impurity) in phenytoin powder. The method depends upon the polarographic activity of benzophenone in Britton-Robinson buffer pH 5.6. The limit of detection was found to be 2.5 x 10(-6) microg ml(-1). Phenytoin has been analysed polarographically after oxidation with alkaline permanganate to give benzophenone; the limit of detection was found to be 6 x 10(-6) microg ml(-1).

Spectrophotometric investigation of the formed chelate between timonacic and palladium(II) and its analytical applications

A simple spectrophotometric method for the determination of timonacic is presented. The procedure is based on the chelate formation with palladium(II) chloride in buffered medium. The optimum conditions for the complex formation were ascertained and the method was developed for the determination of timonacic in the concentration range of 28-48 micrograms ml-1. The emperical formula of the formed complex was determined, by applying different spectrophotometric methods, at optimum pH of 4.8 and an ionic strength of mu = 0.5. The stoichiometric ratio was found to be 2:1 (timonacic/palladium) as calculated by the mole ratio, continuous variations and Asmus methods. The continuous variations and Nash methods were applied for the determination of the conditional stability constant of the formed yellow-water soluble complex and was found to be 3.27 x 10(7). The proposed methods was found to be suitable for the determination of timonacic in bulk and in its pharmaceutical tablets.

High-Performance Liquid Chromatographic and Derivative Ultraviolet Spectrophotometric Determination of Pindolol and Clopamide Mixture in Tablets

Abstract Two rapid assay procedures based on high performance liquid chromatography (HPLC) and derivative ultraviolet (UV) spectrophotometry have been developed for the simultaneous determination of pindolol and clopamide in two component tablets. An HPLC assay with RP-18 column, of 250 × 4.6 mm ID as dimension and 10 μm silica particles, was used. The mobile phase consisted of water-methanol-acetonitrile (50–45–5) with pH of 3 and a flow rate of 1.5 ml min−1. Detection was at 264 nm with a band width of 10 nm. The derivative spectrophotometric procedure depends on the measurements of 2D amplitude in methanol at 264 nm for pindolol and ▴1D amplitude of the delta absorption spectra (methanolic HCl -methanolic NaOH) at 249 nm for clopamide. For HPLC procedure the calibration graphs were linear in the ranges of 10–20 and 5–10 μg ml−1 for pindolol and clopamide, respectively. For the derivative method, they were linear in the ranges of 10–26 and 10–20 μg ml−1 for pindolol and clopamide, respectively. The cali...