Samiha A. Hussein

Spectrofluorimetric method for determination of some angiotensin II receptor antagonists

A simple, rapid, accurate and highly sensitive spectrofluorimetric method has been developed for determination of some angiotensin II receptor antagonists (AIIRAs), namely Losartan potassium (Los-K), Irbesartan (Irb), Valsartan (Val) and Candesartan cilexetil (Cand) in pure forms as well as in their pharmaceutical dosage forms. All the variables affecting the relative fluorescence intensity (RFI) were studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9982–0.9991) were obtained over the concentration range from 0.006 μg/mL to 1.7 μg/mL. Good accuracy and precision were successfully obtained for the analysis of tablets containing each drug alone or combined with hydrochlorothiazide (HCTZ) without interferences from the co-formulated HCTZ or the additives commonly present in tablets.

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 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.

Utility of quercetin for determination of some tertiary amine and quaternary ammonium salts

A simple and sensitive spectrophotometric method for the assay of eight drugs containing quaternary ammonium or tertiary amine moieties is described. The method is based on the interaction of these drugs with quercetin after its oxidation with N-bromosuccinimide (as counter ion) to give highly colored ion-pairing complexes extractable with organic solvents. The absorbances of the colored complexes are measured in the range of 528-560 nm. Beers law is obeyed for the studied drugs in the range 5-30 mug ml(-1). The method is successfully applied to the analysis of the studied drugs in commercial dosage forms.

A sensitive spectrophotometric method for the determination of H2-receptor antagonists by means of N-bromosuccinimide and p-aminophenol

A sensitive spectrophotometric method for the determination of H2-receptor antagonists by means of N-bromosuccinimide and p-aminophenol A simple, accurate and sensitive spectrophotometric method for determination of H2-receptor antagonists: cimetidine (CIM), famotidine (FAM), nizatidine (NIZ), and ranitidine hydrochloride (RAN) has been fully developed and validated. The method was based on the reaction of these drugs with NBS and subsequent measurement of the excess N-bromosuccinimide by its reaction with p-aminophenol to give a violet colored product (λmax at 552 nm). Decrease in the absorption intensity (ΔA) of the colored product, due to the presence of the drug, was correlated with its concentration in the sample solution. Different variables affecting the reaction were carefully studied and optimized. Under optimal conditions, linear relationships with good correlation coefficients (0.9988--0.9998) were found between ΔA values and the corresponding concentrations of the drugs in a concentration range of 8--30, 6--22, 6--25, and 4--20 μg mL-1 for CIM, FAM, NIZ, and RAN, respectively. Limits of detection were 1.22, 1.01, 1.08, and 0.74 μg mL-1 for CIM, FAM, NIZ, and RAN, respectively. The method was validated in terms of accuracy, precision, ruggedness, and robustness; the results were satisfactory. The proposed method was successfully applied to the analysis of the above mentioned drugs in bulk substance and in pharmaceutical dosage forms; percent recoveries ranged from 98.5 ± 0.9 to 102.4 ± 0.8% without interference from the common excipients. The results obtained by the proposed method were comparable with those obtained by the official methods. Osjetljiva spektrofotometrijska metoda za određivanje antagonista H2-receptora uz uporabu N-bromsukcinimida i p-aminofenola Razvijena je i validirana ispravna, jednostavna i osjetljiva spektrofotometrijska metoda za određivanje antagonista H2-receptora: cimetidina (CIM), famotidina (FAM), nizatidina (NIZ) i ranitidin hidroklorida (RAN). Metoda se temelji na reakciji tih ljekovitih tvari s N-bromsukcinimidom (NBS). Višak N-bromsukcinimida određuje se nakon reakcije s p-aminofenolom s kojim daje ljubičasti produkt (λmax pri 552 nm). Smanjenje apsorpcijskog intenziteta (ΔA) obojenog produkta, zbog prisutnosti ljekovite tvari korelirano je s njegovom koncentracijom u otopini uzorka. Proučavane su različite varijable koje utječu na reakciju. Linearno koncentracijsko područje za CIM, FAM, NIZ i RAN, s koeficijentom korelacije od 0,9988 do 0,9998, iznosi 8--30, 6--22, 6--25 odnosno 4--20 μg mL-1. Granice detekcije bile su 1,23, 1,02, 1,09 i 0,75 g mL-1 za CIM, FAM, NIZ, odnosno RAN. Predložena metoda je uspješno primijenjena za analizu navedenih ljekovitih tvari i ljekovitih pripravaka. Nepreciznost od 0,7 do 1,2% i visoka ispravnost (analitički povrat između 98,5 i 102,4%), bez interferencije uobičajenih pomoćnih tvari, ukazuju na dobru analitičku metodu. Rezultati dobiveni predloženom metodom usporedivi su s rezultatima dobivenim službenom metodom.

Colorimetric determination of theophylline and aminophylline with diazotized p-nitroaniline

The reactions of theophylline and aminophylline with diazotized p-nitroaniline in alkaline medium have been studied and developed into a sensitive assay for both drugs. The yellow azo-dyes formed with theophylline and aminophylline show maximum absorption at 440 and 410 nm respectively. Beers law is valid within the concentration range 2-16 mug/ml for theophylline and 1-8 mug/ml for aminophylline. All variables which affect the reactions were studied and optimized. The proposed method has been successfully applied to determination of the drugs in their commercially available dosage forms. Statistical analysis of the results revealed that the proposed method is as precise and accurate as the official USP procedure.

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.