Fawzy A. El-Yazbi

Spectrophotometric and spectrofluorometric methods for the assay of lisinopril in single and multicomponent pharmaceutical dosage forms

Simple and sensitive methods are described for the assay of lisinopril in tablets. The first method (A) is based on the reaction of the drug with chloranil in aqueous solution of pH 9.5 to give yellow colour measured at 346 nm. The second method (B) is based upon the interaction of lisinopril with dichlone resulting in the formation of an intense purple colour measured at 580 nm. The third method (C) depends on the reaction of the drug with acetylacetone and formaldehyde to form a coloured condensation product measured at 356 nm and also has a strong fluorescence at 475 nm (lambda(ex) 410 nm). This method is extended to determine lisinopril in binary mixtures with hydrochlorothiazide. The last method (D) depends on measuring the first and second derivative spectra of lisinopril. Moreover, the derivative method is used as stability-indicating method where lisinopril can be determined in presence of its degradation products. The proposed methods proved to be suitable for a rapid quality control of commercial dosage forms. The results obtained were precise and accurate.

Spectrophotometric methods for the determination of benazepril hydrochloride in its single and multi-component dosage forms

Three sensitive and accurate methods are presented for the determination of benazepril in its dosage forms. The first method uses derivative spectrophotometry to resolve the interference due to formulation matrix. The second method depends on the color formed by the reaction of the drug with bromocresol green (BCG). The third one utilizes the reaction of benazepril, after alkaline hydrolysis, with 3-methylbenzothialozone (MBTH) hydrazone where the produced color is measured at 593 nm. The latter method was extended to develop a stability-indicating method for this drug. Moreover, the derivative method was applied for the determination of benazepril in its combination with hydrochlorothiazide. The proposed methods were applied for the analysis of benazepril in the pure form and in tablets. The coefficient of variation was less than 2%.

Spectrophotometric determination of aldehydes in alcohols

A simple and sensitive method was described for the determination of formaldehyde and acetaldehyde in methanol and ethanol, respectively. A limit for aldehydes in alcohols is a necessary requiremen...

Determination of Some Cephalosporins Using Derivative Spectrophotometry

Abstract A rapid and simple method for the determination of cephalexin, cephalothin sodium and cephradin without prior separation from their alkali-induced degradation products is presented. By measuring the values of the first and second derivative spectra at certain wavelengths, the concentration of the intact drug can be calculated directly without interference of degradation products. The method was proved using synthetic mixtures of the intact drugs with their degradation products, and its suitability to monitor the stability of the drugs was demonstrated.

Spectrophotometric Determination of Enalapril Maleate and Ramipril in Dosage Forms

Abstract Three sensitive and accurate spectrophotometric methods have been developed for the assay of enalapril maleate and ramipril, each in its dosage forms. These methods depend on the reaction of the drugs with p-chloranilic acid, the reaction with picric acid, and the ion-pair salt formation with bromocresol green. The proposed methods have been applied to the analysis of these drugs in their commercial tablets. The results obtained were precise and accurate.

Spectrophotometric and titrimetric determination of clindamycin hydrochloride in pharmaceutical preparations

Two simple and accurate methods are described for the determination of clindamycin hydrochloride. The spectrophotometric method involves the oxidation of the sulfur atom in this drug with potassium iodate in acidic medium with the liberation of iodine and subsequent extraction with cyclohexane followed by measuring the absorbance at 520 nm. The titrimetric method involves direct titration of the drug with N-bromosuccinimide. The relative standard deviation for both methods was less than 1%. The proposed methods were applied to the determination of the drug in pure and capsule forms.

Spectrophotometric and Spectrofluorimetric Methods for the Determination of Terazosin in Dosage Forms

Abstract Five simple and accurate methods are presented for the determination of terazosin (TZ) in tablets. These methods are based on: the direct measurements of the first and second derivative spectra of samples (A), the reaction of TZ with chloranil (CH) in aqueous solution of pH 9 to give an intense yellow color measured at 340 nm (B), the reaction of the drug with mercurochrome (MER) in aqueous alkaline medium to give an intense red color measured at 543 nm (C), the formation of an ion-pair salt between the drug and bromocresol purple (BCP) with subsequent absorbance measurements at 412 nm (D), and a sensitive fluorimetric method (E). The latter method was extended to determine TZ in presence of its degradation products.

Spectrophotometric and Spectrofluorimetric Determination of Ofloxacin

Abstract Two methods are presented for the analysis of ofloxacin. The first method is based on the application of Amax, ΔA, first and second derivative techniques for its determination in bulk powder, tablet form, and in urine. The use of absorbance and derivative maxima ratios as purity indices has been discussed. The second depends on the fluorescence characteristics of ofloxacin in acidic solutions. The spectrofluorimetric method is 10 times more sensitive than the spectrophotometric one. The accuracy and reproducibility of the methods were shown by the within day and between day coefficient of variation (less than 3%).

Determination of cholesterol in sera.

Two methods are described for the determination of cholesterol in sera. The principle of these methods is that hydrogen peroxide, liberated by action of cholesterol esterase and cholesterol oxidase on cholesterol esters (or free cholesterol), is coupled under the catalytic effect of peroxidase with 4-hydroxyphenylacetic acid to form a fluorescent product, and with 3-methylbenzothiazoline-2-one hydrazone and 3-dimethylaminobenzoic acid to obtain a coloured compound. The main advantages of these procedures over comparable methods are their short reaction time, high sensitivity and low cost of the tests.

Derivative spectrophotometric analysis of two-component mixtures using a compensation technique

A method based on the compensation technique is presented for the derivative spectrophotometric determination of binary mixtures with overlapping spectra. By using ratios of the derivative maxima, the exact compensation of either component in the mixture can be achieved, followed by its determination. The personal judgement of the correct evaluation of the balance point is eliminated. The results obtained were precise and accurate.