Pakinaz Y. Khashaba

Analysis of some antifungal drugs by spectrophotometric and spectrofluorimetric methods in different pharmaceutical dosage forms

Simple spectrophotometric and spectrofluorimetric methods are suggested for the determination of antifungal drugs; clotrimazole, econazole nitrate, ketoconazole, miconazole and tolnaftate. Spectrophotometric one depends on the interaction between imidazole antifungal drugs as n-electron donor with the pi acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in methanol or with p-chloranilic acid (p-CA) in acetonitrile. The produced chromogens obey Beers law at lambda(max) 460, and 520 nm in the concentration range 22.5-200 and 7.9-280 microg ml(-1) for DDQ, and p-CA, respectively. Spectrofluorimetric method is based on the measurement of the native fluorescence of ketoconazole at 375 nm with excitation at 288 nm and or the induced fluorescence after alkaline hydrolysis of tolnaftate with 5 M NaOH solution at 420 nm with excitation at 344 nm. Fluorescence intensity versus concentration is linear for ketoconazole at 49.7-800 ng ml(-1) while for tolnaftate, it is in the range of 20.4-400 ng ml(-1). The proposed methods were applied successfully for the determination of all the studied drugs in their pharmaceutical formulations.

Spectrofluorimetric analysis of certain macrolide antibiotics in bulk and pharmaceutical formulations

The macrolides (erythromycin, erythromycin esters, azithromycin dihydrate, clarithromycin and roxithromycin) can be analyzed by a simple spectrofluorimetric method based on the oxidation by cerium(VI) in the presence of sulphuric acid and monitoring the fluorescence of cerium(III) formed at lambda(ex) 255 nm and lambda(em) 348 nm. All variables affecting the reaction conditions as cerium(VI), sulphuric acid concentrations, heating time, temperature and dilution solvents were carefully studied. Linear calibration graphs were obtained in the range of 42.6-1200 ng ml(-1) with a percentage relative standard deviation in the range of 0.014-0.058%. Quantitation and detection limits were calculated. The method was applied successfully for the assay of the studied drugs in pure and pharmaceutical dosage forms as tablets, capsules and suspension. Recovery experiments revealed recovery of 98.3-100.8%. The effect of potential interference due to common ingredients as glucose, sucrose, lactose, citric acid, and propylene glycol was investigated. Applying standard addition method shows a recovery of 97.7-100.9% macrolide antibiotics from their corresponding dosage forms.

Spectrophotometric determination of clotrimazole in bulk drug and dosage forms

A simple, specific, rapid and sensitive spectrophotometric method has been developed for the assay of clotrimazole, in bulk drug and its pharmaceutical preparations. This method is based on the ion-pair complex reaction of clotrimazole and methyl orange in aqueous methanol, and in the presence of citric acid. The chromogen, being extractable with chloroform, could be measured quantitatively at 422 nm. All variables were studied to optimize the reaction conditions. Regression analysis of beers plot showed good correlation in a general concentration range of 2-14 mu/ml. The proposed method has been successfully applied for the analysis of the bulk drug and its dosage forms such as powder, vaginal tablets, topical solution and creams. No interference was observed from betamethasone dipropionate (Lotriderm cream) or dexamethasone acetate and azidamphenicol (Baycuten cream) or other common pharmaceutical adjuvants. In addition, this method was also found to be specific for the analysis of clotrimazole in the presence of its hydrolytic products as well as imidazole, as a possible impurity.

Charge-Transfer Complexation for Spectrophotometric Assay of Certain Imidazole Antifungal Drugs

Abstract A spectrophotometric method is described for the assay of some antifungal agents containing an imidazole ring: clotrimazole, econazole, ketoconazole and miconazole. The method is based on the formation of a charge-transfer complex between the drug as n-electron donor and iodine as [sgrave]-acceptor. The product exhibited two absorption maxima at 290 and 377 nm; measurements are made at 290 nm. Beers law is obeyed in a concentration range of 1-40 μg/ml. The method is rapid, simple and sensitive and can be applied to the analysis of some commercial dosage forms without interference. A detailed investigation of the formed complex was made with respect to its composition, association constant and free energy change. To whom all correspondence should be addressed.

Determination of trimetazidine HCl by adsorptive stripping square-wave voltammetry at a glassy carbon electrode

The adsorptive and electrochemical behavior of trimetazidine hydrochloride on a glassy carbon electrode were investigated in acetate buffer solution by using cyclic and square-wave voltammetry. Cyclic voltammetric studies indicated the oxidation of trimetazidine hydrochloride at the electrode surface through a single two-electron irreversible step and fundamentally controlled by adsorption. The solution condition and instrumental parameters were optimized for the determination of the authentic drug using adsorptive square wave stripping voltammetry. Trimetazidine hydrochloride gave a sensitive adsorptive oxidative peak at 0.750 V (vs. Ag/AgCl). The oxidation peak was used to determine authentic trimetazidine hydrochloride concentration in the range 5.0 x 10(-8)-5.0 x 10(-6) M with a detection limit of 2.0 x 10(-8) M. The procedure was successfully applied for assay of trimetazidine hydrochloride in the tablet dosage form (Vastarel). A mean recovery of 94.7% with a relative standard deviation (R.S.D.) of 0.88% was obtained. Applicability to assay the drug in urine samples was illustrated. The peak current was linear with the drug concentration in the range 17-85 microg per ml urine. The detection limit was 1.7 microg ml(-1) urine.

Selective spectrophotometric determination of ascorbic acid in drugs and foods

A new analytical method was developed for the determination of ascorbic acid. The method is based on the reaction of ascorbic acid with 4-chloro-7-nitrobenzofurazane (NBD-Cl) in the presence of 0.2M sodium hydroxide, where a bluish green colour (lambda(max) 582 nm) is developed after dilution with 50% (v/v) aqueous acetone solution. Beers law was obeyed in a concentration range of 5-20 microg ascorbic acid/ml with a good correlation coefficient (r = 0.9990). The method was found to be highly specific for the determination of ascorbic acid in the presence of dehydro-ascorbic acid, all other vitamins and minerals possibly present in multivitamin preparations, rutin, salicylamide, acetyl salicylic acid, paracetamol, caffeine, phenylephrine hydrochloride and dipyrone. Moreover, the proposed procedure was also successfully applied for the determination of ascorbic acid in some canned and fresh fruit juices, some vegetables and infant milk products without interference from coloured and other substances present in the plant extracts.

Spectrodensitometric determination of some pharmaceutical mixtures containing proton pump inhibitors

Two ultraviolet (UV)—spectrodensitometric methods were proposed for the separation and determination of binary and ternary mixtures containing proton pump inhibitors (PPIs). Method A was developed for the assay of omeprazole, panoprazole, rabeprazole, and lansoprazole in binary mixtures with domperidone (DOM) using their isoabsorptive points. Method B was developed for the determination of a ternary mixture containing omeprazole, tinidazole, and clarithromycin. It depends on using malonic acid–acetic anhydride as a spraying reagent to form yellow color (for omeprazole) and dark brown color (for clarithromycin) that are measured at λmax = 350 nm and λmax = 492 nm, respectively, while tinidazole was measured by UV at λmax = 310 nm. For method A, Beer’s law was obeyed for all studied PPIs and domperidone in the concentration range of 180–1440 and 120–720 ng spot−1, respectively. The detection limits for proton pump inhibitors and domperidone were 48.05–73.45 and 30.74–32.50 ng spot−1, respectively, and the quantitation limits were 145.59–222.47 and 93.14–98.48 ng spot−1, respectively. For method B, Beer’s law was obeyed for omeprazole, clarithromycin, and tinidazole in the concentration range of 180–480, 2250–6000, and 30–180 ng spot−1, respectively. The detection limits for omeprazole, clarithromycin, and tinidazole were 20.36, 272.60, and 2.05 ng spot−1, respectively, and the quantitation limits were 61.7, 825.9, and 6.2 ng spot−1, respectively, for the investigated drugs.

Simultaneous voltammetric analysis of anti-ulcer and D2-antagonist agents in binary mixture using redox sensor and their determination in human serum

Pencil graphite electrode was successfully modified with a thin film of poly (eriochrome black T) and applied for the sensitive and selective voltammetric simultaneous determination of pantoprazole sodium and domperidone in a binary mixture. The preparation and basic electrochemical behavior of poly (eriochrome black T) film on the Pencil graphite electrode were investigated. The modified electrode has exhibited very high electro-catalytic activity towards the cited mixture. The anodic peaks of the both species were well defined with enhanced oxidation peak currents. Under the optimum conditions, the linearity ranges were 0.4-55×10-7M and 0.1-34×10-7M for pantoprazole sodium and domperidone, respectively with detection limits of 0.12×10-7M and 0.04×10-7M for pantoprazole sodium and domperidone, respectively. The proposed sensor has been successfully applied in the analysis of pantoprazole sodium and domperidone in synthetic binary mixtures and human serum.

Utility of Diazotized 4 - Amino-6-Chloro-1,3-Benzene Disulphonamide for the Spectrophotometric Determination of 8-Hydroxquinolines and Dibenzazepines.

The present study is based on the interaction of diazotized 4-amino-6-chloro-1,3-benzene disulphonamide (DACBS) with 8-hydroxyquinolines in slightly alkaline medium and with dibenzazepines in strongly acidic medium to form red coloured products in the range of 500- 555 nm. Under optimum reaction condition, Beers law is obeyed in the concentration range 0.5-25 μg/ml for 8-hydroxyquinolines and 1.0-25 μg/ml for dibenzazepines. The stoichiometry of the reaction was investigated and was found to be 1:1 for all the studied drugs. Interference due to other co-formulated drugs, common additives and excepients was studied. The proposed method was applied successfully for the determination of the cited drugs in their pharmaceutical preparations and results were comparable with that of the official, reported method.

Development of a novel and cost-effective redox sensor for voltammetric determination of pantoprazole sodium during pharmacokinetic studies

A pencil graphite electrode modified with poly (bromocresol green (BCG)) was prepared by electro-polymerization process for the determination of pantoprazole sodium. The surface morphology and structure of poly (BCG) film were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The determination of pantoprazole sodium in Britton–Robinson buffer (pH 7.0) was carried out by square wave adsorptive stripping voltammetric technique. Under optimum conditions, the linear response of the peak with concentration of the cited drug was in the range of 6.6–360 × 10−8 M with limit of detection of 2.2 × 10−8 M. Moreover, the poly (BCG)-modified electrode has been successfully applied to determine pantoprazole sodium in tablets, vials and during pharmacokinetic studies.