Abdel-Maboud I. Mohamed

Spectrophotometric determination of some dibenzazepines

Abstract Simple and sensitive method is proposed for determination of four di-benzazepine derivatives. The method is based on the oxidation of dibenzazepines by potassium dichromate in acid medium. The reaction was followed spectrophoto-metrically by measuring the rate of change in absorbance of the coloured products at 670 nm. Linear calibration graphs from 5-50 μg/ml of the final solutions are obtained for all the studied drugs. The method has been successfully applied to the determination of dibenzazepines in some commercial and laboratory prepared tablets. The results were compared statistically with those obtained by official procedures.

Spectrophotometric Determination of Some Pharmaceutical Compounds Using 2,2-Diphenyl-1-picrylhydrazyl

Abstract A spectrophotometric method for the determination of some pharmaceutical amides, hydrazides and thiols is described. The method is based on the reaction of the studied drugs with 2,2-diphenyl-1-picryl hydrazyl (DPPH). The latter is employed to abstract a hydrogen atom from the drugs thereby promoting a process of radical coupling. This results in a reduction of the violet colour of DPPH with the formation of the yellow coloured 2,2-diphenyl-1-picrylhydrazine (DPPH2). This fading in colour of DPPH reagent depends on the concentration of the drug being determined. Beers law is obeyed in the ranges of 1–5 μg/ml (for isocarboxazid and gliclazide), 0.25–2.5 μg/ml (for isoniazid), 0.5–5 μg/ml (for iproniazid), 1–7 μg/ml (for tolazamide), 2–15 μg/ml (for captopril) and 1–6 μg/ml (for sulphathiourea). The validity of the method was tested by analysing the studied drugs in pure form as well as in tablets. Results of analyses were compared statistically with the official or reported methods.

Spectrophotometric determination of some dibenzazepine drugs by electrophilic coupling

Two sensitive spectrophotometric methods for the determination of imipramine hydrochloride, clomipramine hydrochloride, desipramine hydrochloride, and trimipramine maleate in bulk and in dosage forms are described. The first method is based on the interaction of diazotized p-nitroaniline (DPNA) with the dibenzazepine drug in 5M hydrochloric acid. The second is based on the oxidative coupling of the dibenzazepine drug with 3-methylbenzothiazolin-2-one hydrazone (MBTH) in the presence of ammonium iron(III) sulphate in 0.1M hydrochloric acid. The resulting chromophores are measured at 575 nm (for the DPNA method) or at 620-630 nm (for the MBTH method), and are stable for at least 24 hr. The commonly encountered excipients and additives do not interfere with the determinations. Results from the analysis of pure drugs, commercial tablets and laboratory-prepared tablets by these methods agree well with those of official methods.

Spectrophotometric determination of some dibenzazepines with picryl chloride

A simple and sensitive spectrophotometric method has been developed for the determination of some dibenzazepines, based on reaction with picryl chloride in chloroform medium and measurement at 395 nm. Beers law is obeyed in concentration ranges 0.1-1.0 microg/ml for imipramine hydrochloride, trimipramine maleate and opipramol dihydrochloride, 0.16-1.6 microg/ml for desipramine hydrochloride and 0.4-2.4 microg/ml for clomipramine hydrochloride. The method was applied successfully to the determination of dibenzazepines in tablets and the results were comparable to those obtained by official procedures.

Use of p-benzoquinone for the spectrophotometric determination of certain sulphonamides.

A simple spectrophotometric method for the determination of 15 sulphonamides in bulk and in dosage forms is described. The method is based on the interaction of p-benzoquinone with sulphonamides in 0.1 M hydrochloric acid. The resulting chromophore is measured at 500 nm. The effects of different variables on colour development were established. Beers law was obeyed in a concentration range of 10-50 micrograms ml-1. Results from the analysis of different sulphonamide tablets and ophthalmic solutions marketed locally were in good agreement with that of a reference method. Correlations between A1cm(1%) and certain physical parameters such as pKa values, characteristic volume Vx, and molecular connectivity indices 1X and 1Xv were determined by linear regression equations. A poor correlation was found between A1cm(1%) and bulkiness parameters but a highly significant negative correlation was obtained with apparent pKa values.

Utility of Certain π-Acceptors for the Spectrophotometric Determination of Isoniazid

Abstract The interaction of isoniazid with three selected π-acceptors in an aqueous-acetonitrile solution of pH 9.0–9.5 was found to give intensely coloured products. A spectrophotometric method based on this reaction is described for quantitation of isoniazid. The determination of products was carried out at 445 nm for chloranil, 450 nm for bromanil and around 750 nm for 7,7,8,8-tetracyanoquinodimethane. The effect of several variables on the colour development was studied. The molecular ratios of the reactants have been established. The proposed methods have been applied successfully for analysis of isoniazid in pure samples and in a number of its pharmaceutical preparations with good accuracy and precision. Results were compared to those obtained by the official methods.

Utility of certain π-acceptors for the spectrophotometric determination of gliclazide and tolazamide

The reaction of gliclazide and tolazamide with three selected π-acceptors in acetonitrile-water (9 + 1) at pH 9.0–9.5 was found to give intensely coloured products. A method based on this reaction is proposed for the determination of trace amounts of both drugs. Quantification was carried out at 445 nm for p-chloranil, 450 nm for p-bromanil and ca. 750 nm for 7,7,8,8-tetracyanoquinodimethane. The molar ratios of the reactants were established and the experimental conditions giving maximum absorption were also studied. The proposed procedures were applied successfully to the determination of both drugs either in pure samples or in tablets with good accuracy and precision. The results were compared with those obtained by the official USP method.

Use of 7,7,8,8-tetracyanoquinodimethane for spectrophotometric determination of certain local anaesthetics and procainamide hydrochloride

A simple and rapid spectrophotometric procedure has been developed for the determination of four local anaesthetics containing a free primary amine moiety and of procainamide hydrochloride as the drug substances and in dosage forms. The method is based on the reaction of the drug with 7,7,8,8-tetracyanoquinodimethane in alkaline solution to produce yellow products. The chromogen was measured at 473 nm. The effects of several variables on colour development were established. Jobs plots of absorbance versus molar ratio of drug to reagent indicated a 1:1 ratio for all the drugs studied. Results of the analysis of drug substances and their dosage forms by the proposed method are in good agreement with those obtained by the USP XX method.

Spectrophotometric determination of some benzothiadiazine diuretics with 7,7,8,8-tetracyanoquinodimethane

A new spectrophotometric method for the determination of some benzothiadiazine drugs is presented, based on reaction with 7,7,8,8-tetracyanoquinodimethane in sodium acetate medium and measurement at 578 nm. Beers law is obeyed in the concentration range 0.7-6.0 mug/ml for all eight drugs tested.

A rapid spectrophotometric method for determination of piperazine.

A spectrophotometric method has been developed for the determination of piperazine and its salts (citrate, phosphate, and tartrate) without prior separation, based on the interaction of piperazine or any of its salts with phenothiazine and N-bromosuccinimide in aqueous methanol. The products exhibit absorption maxima at 448, 595 and 645 nm. Measurements are made at 595 nm. Beers law is obeyed in the concentration range 0.5-5 mug/ml for piperazine salts and 0.5-3 mug/ml for piperazine hexahydrate. The method is rapid, simple and successful for analysis of some pharmaceutical preparations.