Bahia A. Moussa

Determination of some aminobenzoic acid derivatives : glafenine and metoclopramide

Simple, sensitive and accurate spectrophotometric methods for the determination of glafenine and metoclopramide hydrochloride are described. The first method is based on the oxidation of glafenine with iodic acid in strong acid medium to give a coloured diphenylbenzidine derivative and subsequent measurement of the coloured product at 509 nm. Beers law is obeyed over the concentration range 2.5-20 microg ml(-1). The second method depends on the interaction of metoclopramide hydrochloride with p-dimethylaminocinnamaldehyde, to give a red coloured schiffs base with an absorbance maximum at 548 nm. Obedience to Beers law is achieved over the concentration range 5-30 microg ml(-1). First-derivative method is used to overcome the slight interference of p-dimethylaminocinnamaldehyde reagent blank at the wavelength of measurement. Linearity between the peak heights at 576 nm versus concentration range 5-25 microg ml(-1) metoclopromide hydrochloride is obtained. The proposed methods have been successfully applied to the determination of these drugs in commercial products without interference. The validity of the methods is assessed by applying the standard addition technique, the relative standard deviation is less than 1%. The proposed methods are compared with reference methods with good agreement.

Simultaneous Densitometric TLC Analysis of Olmesartan Medoxomil and Hydrochlorothiazide in the Tablet Dosage Form

A simple, rapid, and selective densitometric thin-layer chromatographic (TLC) method has been established and validated for simultaneous quantitative analysis of olmesartan medoxomil and hydrochlorothiazide in the presence of olmesartan medoxomil degradation products. Chromatography was performed on aluminum foil-backed HPTLC plates coated with 0.2 mm layers of nano-silica gel 60 F254 as stationary phase. RF values of olmesartan medoxomil, its degradation products, and hydrochlorothiazide were significantly different when chloroform-methanol-formic acid 8:1.5:0.5 (v/v) was used as mobile phase. Detection was performed at 260 nm and 272 nm for olmesartan medoxomil and hydrochlorothiazide, respectively. Regression plots revealed good linear relationships in the concentration range 0.05–1 mg mL−1. Accuracy was checked by conducting recovery studies; average recovery was 100.35 ± 1.060 and 99.91 ± 1.154 for olmesartan medoxomil and hydrochlorothiazide, respectively. The amounts of the drugs in the dosage formulation were 102.78 ± 1.525% of the label claim for olmesartan medoxomil and 103.09 ± 1.259 for hydrochlorothiazide. Method validation was performed in accordance with USP guidelines.

DETERMINATION OF CERTAIN ANTISPASMODIC DRUGS AS SINGLE INGREDIENT, MEBEVERINE HYDROCHLORIDE, AND IN TWO COMPONENT MIXTURES, MEBEVERINE HYDROCHLORIDE–SULPIRIDE AND ISOPROPAMIDE IODIDE–TRIFLUOPERAZINE HYDROCHLORIDE

ABSTRACT Two simple and sensitive methods are described for the quantitative determination of mebeverine hydrochloride as single ingredient. The first method depends on the application of quantitative 1H-NMR spectroscopy using deuterated chloroform and hexamine as an internal reference standard. The second method is based on measuring the native fluorescence of mebeverine hydrochloride in 0.1 N sulphuric acid at 360 nm with excitation at 290 nm. Furthermore simultaneous determinations of two component mixtures, mebeverine hydrochloride with sulpiride and isopropamide iodide with trifluoperazine hydrochloride are presented using first-derivative and second-derivative UV-spectrophotometry, respectively. The proposed methods have been successfully applied to the determination of the cited drugs in commercial tablets. Compared with the reference methods, the proposed methods are more sensitive, with good accuracy and reproducibility.

Simultaneous Determination of Amlodipine Besylate and Atorvastatin Calcium in Binary Mixture by Spectrofluorimetry and HPLC Coupled with Fluorescence Detection

Caduet tablets are novel prescription drug that combines amlodipine besylate (AM) with atorvastatin calcium (AT). A spectrofluorimetric and an HPLC-fluorescence detection methods were developed for simultaneous determination of both drugs in tablets. In the spectrofluorimetric method, native fluorescence of AM and AT were measured in methanol at 442 and 369 nm upon excitation at 361 and 274 nm, respectively. The emission spectrum of each drug reveals zero value at the emission wavelength of the other drug, thus allowing their simultaneous determination without interference. In the HPLC method, separation of AM and AT was achieved within 8 minutes on a C18 column using acetonitrile:phosphate buffer (0.015 M, pH 3) (45:55, v/v) as the mobile phase. Fluorescence detection was carried out using excitation wavelengths 361 and 274 nm and emission wavelengths 442 and 378 nm for AM and AT, respectively. Excellent linearity was observed. Careful validation proved advantages of the new methods: high sensitivity, accuracy, selectivity and suitability for quality control laboratories.

Colorimetric analysis of some diuretic drugs: hydrochlorothiazide and spironolactone

Two convenient spectrophotometric methods were developed for the determination of hydrochlorothiazide and spironolactone. A specific colour reaction for the determination of hydrochlorothiazide is reported. One method is based on the reaction of hydrochlorothiazide withn-butylamine and cobaltous chloride in anhydrous methanol. A blue-violet colour is produced and is measured at 570 nm. A highly selective colorimetric method was adopted for the analysis of spironolactone by reacting with isoniazid forming a coloured hydrazone derivative and subsequent measurement of the coloured product at 405 nm.

Colorimetric determination of parasiticides hycanthone and metronidazole

Sensitive, simple and accurate methods are described for the colorimetric determination of hycanthone and metronidazole. The methods are based on the reaction of hycanthone with 2,4-dimtrophenylhydrazine and the separated hydrazone when treated with ethanolic potassium hydroxide solution, gives a wine red colour. Metronidazole on reduction with zinc and hydrochloric acid forms complex with p-dimethylaminocinnamaldehyde which is highly coloured. The methods are applicable to nucrogram amounts and can be used successfully for the determination of hycanthone and metronidazole in dosage forms.

Spectrofluorimetric determination of gemifloxacin mesylate and linezolid in pharmaceutical formulations: Application of quinone-based fluorophores and enhanced native fluorescence

Abstract Quinone-based fluorophores and enhanced native fluorescence techniques were applied for a fast quantitative analysis of gemifloxacin mesylate (GEM) and linezolid (LIN) in pharmaceutical formulations. For this purpose, three sensitive, accurate and precise spectrofluorimetric methods were developed. GEM, as an n-electron donor, reacts with 7,7,8,8-tetracyanoquinodimethane (method A) and 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (method B) as п-electron acceptors, forming charge transfer complexes that exhibit high fluorescence intensity at 441 and 390 nm upon excitation at 260 and 339 nm, respectively. Method C depends on measurement of enhanced native fluorescence of LIN in phosphate buffer (pH 5) at 380 nm upon excitation at 260 nm. Experimental factors affecting fluorescence intensity were optimized. Linearity was obtained over concentration ranges 50-500, 10-60 and 20-400 ng mL-1 for methods A, B and C, respectively. The developed methods were validated and successfully applied for determination of the cited drugs in tablets.

ACID- ALKALI DEGRADATION STUDY ON OLMESARTAN MEDOXOMIL AND DEVELOPMENT OF VALIDATED STABILITY-INDICATING CHROMATOGRAPHIC METHODS

A reversed phase liquid chromatography (RP-HPLC) and thin layer chromatography (HPTLC) densitometry methods as a stability indicating assays of olmesartan medoxomil in presence of its acid or alkaline induced degradation products were developed. Olmesartan medoxomil and its degradation products were analyzed by HPLC equipped with UV-Variable wave length detector at 257 nm where quantitation was achieved by isocratic elution on Agilent, Exclipse XDB- C 18 column with mobile phase composed of acetonitrile: methanol: water: glacial acetic acid (40:35:25:0.1 v/v/v/v) at flow rate 1ml min.-1. HPTLC was performed on aluminum packed Nano silica gel 60 F 254 TLC plates as stationary phase with significant difference in Rƒ values between olmesartan medoxomil and its degradates using chloroform: methanol: formic acid (8:1.5:0.5 v/v/v) as mobile phase. Densitometric evaluation of intact drug was carried out at 260 nm. The calibration curve of olmesartan medoxomil in bulk form was linear from 0.5- 10 µg ml-1 and 0.05- 1 mg ml-1 with mean percentage accuracy 99.97 ± 1.085 % and 100.35 ± 1.060 % for HPLC and HPTLC methods, respectively. The two proposed methods were successfully applied for the determination of olmesartan medoxomil in drug substance and in drug product. Methods validation was tested for linearity; accuracy; precision; selectivity and robustness, according to USP guidelines.

Analysis of some antispasmodic drugs: oxyphencyclimine and glycopyrronium bromide

Oxyphencyclimine hydrochloride (via its tertiary amine group) and glycopyrronium bromide (via its quaternary ammonium group) were analysed by two different colorimetric methods. The first method depends on the dye-salt formation method using tropeolin ooo as the anionic dye and 1,2-dichloroethane as solvent for the extraction of the formed ion pairs. The coloured ion pairs have maximum absorption at 483–486 nm. The second method is based on the use of citric acid-acetic anhydride reagent. The coloured complex has maximum absorption at 562–565 nm.

Resolution of overlapped spectra for the determination of ternary mixture using different and modified spectrophotometric methods

Four new spectrophotometric methods were developed, applied to resolve the overlapped spectra of a ternary mixture of [aliskiren hemifumarate (ALS)-amlodipine besylate (AM)-hydrochlorothiazide (HCT)] and to determine the three drugs in pure form and in combined dosage form. Method A depends on simultaneous determination of ALS, AM and HCT using principal component regression and partial least squares chemometric methods. In Method B, a modified isosbestic spectrophotometric method was applied for the determination of the total concentration of ALS and HCT by measuring the absorbance at 274.5nm (isosbestic point, Aiso). On the other hand, the concentration of HCT in ternary mixture with ALS and AM could be calculated without interference using first derivative spectrophotometric method by measuring the amplitude at 279nm (zero crossing of ALS and zero value of AM). Thus, the content of ALS was calculated by subtraction. Method C, double divisor first derivative ratio spectrophotometry (double divisor (1)DD method), was based on that for the determination of one drug, the ratio spectra were obtained by dividing the absorption spectra of its different concentrations by the sum of the absorption spectra of the other two drugs as a double divisor. The first derivative of the obtained ratio spectra were then recorded using the appropriate smoothing factor. The amplitudes at 291nm, 380nm and 274.5nm were selected for the determination of ALS, AM and HCT in their ternary mixture, respectively. Method D was based on mean centering of ratio spectra. The mean centered values at 287, 295.5 and 269nm were recorded and used for the determination of ALS, AM and HCT, respectively. The developed methods were validated according to ICH guidelines and proved to be accurate, precise and selective. Satisfactory results were obtained by applying the proposed methods to the analysis of pharmaceutical dosage form.