Kamla M. Emara

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.

Selective spectrophotometric method for the determination of ascorbic acid in pharmaceutical preparations and fresh fruit juices

A simple and selective method for the determination of ascorbic acid in pharmaceutical preparations and fresh fruit juices is described. The procedure is based on the reaction of ascorbic acid with the zinc chloride salt of diazotized 1-aminoanthraquinone (Fast Red AL salt) in an acidic medium, followed by development of a blue colour (λmax 630 nm) in alkaline solution. Different variables affecting the colour development were studied and optimized. The method was used to determine between 5 and 25 µg ml–1 of ascorbic acid in the final measured solution. The simplicity of the method permits rapid analysis, suitable for routine control. The method is highly specific for the determination of ascorbic acid in the presence of dehydroascorbic acid and all other vitamins normally encountered with it in pharmaceutical dosage forms. Moreover, the proposed method can also be applied to the determination of ascorbic acid in some fresh fruit juices without interference from coloured and other substances present in the fruit extracts. The reliability of the method was established by parallel determinations against the official British pharmacopoeial method.

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.

Colorimetric determination of isoniazid and its pharmaceutical formulations

Two colorimetric methods for the estimation of isoniazid are developed. The first method depends on coupling of isoniazid with diazotized 1-amino anthraquinone zinc chloride salt (fast red AL salt) to form a red colour (lambda(max) 510 nm). The second one is based on the formation of a green complex (lambda(max) 655 nm) between the acid hydrazide and 2,6-dimethoxy-1,4-benzoquinone (DMBQ). All measurements of the two procedures were carried out in the presence of sodium hydroxide at room temperature (20 +/- 3 degrees C). The two methods are applied for the determination of isoniazid in presence of congenial drugs, vitamins and additives normally encountered with it in pharmaceutical dosage forms. The reliability of these methods was established by parallel determination with the reported and official methods.

Spectrophotometric determination of certain local anaesthetics using 3-methylbenzothiazolin-2-one hydrazone

A rapid spectrophotometric procedure for the determination of benzocaine, procaine hydrochloride and amethocaine hydrochloride in pure and dosage forms has been developed. It is based on coupling the local anaesthetic drug with 3-methylbenzothiazolin-2-one hydrazone in the presence of ammonium iron(III) sulphate in an acidic medium. The resulting stable blue product has a λmax. of either 575 nm (for benzocaine and procaine hydrochloride) or 615 nm (for amethocaine hydrochloride). The molar absorptivities range from 0.6 × 103 to 5.5 × 104 l mol–1 cm–1. Job plots of absorbance versus molar ratio of amine to reagent indicate a 1 : 1 ratio for benzocaine and procaine hydrochloride and a 1 : 2 ratio for amethocaine hydrochloride. Results of analyses of pure drugs and their dosage forms by the proposed method are in good agreement with those obtained by the USP XXI method.

Determination of phenyltoloxamine salicylamide, caffeine, paracetamol, codeine and phenacetin by HPLC.

A reversed-phase high-performance liquid chromatographic method for the determination of six common analgesics (phenyltoloxamine dihydrogen citrate, salicylamide, caffeine, paracetamol, codeine phosphate and phenacetin) is presented. The method is specific for detection and determination of each of these compounds in a complex mixture, without pretreatment. A 10-mum C(18) silica gel stationary phase is used with a methanol-acetonitrile-water-tetrahydrofuran mixture (20:20:55:5 v/v) and spectrophotometric detection at 254 nm. All six components are eluted within 7 min. The method has given good results for three commercial products containing two, three and five active ingredients respectively. Phenacetin, a common analgesic which might be found in other formulations, is used as an internal standard.

Spectrophotometric determination of tetracycline and oxytetracycline in pharmaceutical preparations

A simple, rapid and sensitive spectrophotometric procedure for the assay of tetracycline hydrochloride and oxytetracycline hydrochloride has been developed. 2,2-Diphenyl-l-picrylhydrazyl (DPH), an intensely violet-coloured stable free radical, is changed in colour on reaction with the antibiotics investigated. The decrease in the intensity of the violet colour is used to measure the concentration of the drug. All measurements are made at 520 nm on methanolic solutions of the drug and reagent, buffered at pH 6. Beers law is obeyed in the concentration ranges 2.5-15 and 2.5-20 mug/ml for tetracycline and oxytetracycline respectively. The proposed method has been successfully applied to analysis of the bulk drugs and their pharmaceutical formulations.

Determination of memantine in rat plasma by HPLC-fluorescence method and its application to study of the pharmacokinetic interaction between memantine and methazolamide.

A sensitive high-performance liquid chromatographic method with fluorescence detection was developed to determine memantine (MT) in rat plasma. The method consists of pre-column labeling of MT with 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) and a clean-up step with solid-phase extraction. A good separation of DIB-MT was achieved within 12 min on an octadecylsilica (ODS) column (150 × 4.6 mm i.d.; 5 µm) with a mobile phase of acetonitrile-water (70:30, v/v). The calibration curve prepared with fluoxetine as an internal standard showed good linearity in the range of 10-400 ng/mL (r = .999). The limits of detection and quantitation at signal-to-noise ratios of 3 and 10 were 2.0 and 6.6 ng/mL, respectively. The method was shown to be reliable with precisions of <5% for intra-day and <9% for inter-day as relative standard deviation. The fluorescence property and reaction yield of authentic DIB-MT were also examined. The proposed method was successfully applied to study the pharmacokinetic interaction between MT and methazolamide.

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.

Application of 3-methylbenzothiazolin-2-one hydrazone as a chromogenic reagent for the spectrophotometric determination of certain sulpha drugs

The oxidative coupling reaction of 3-methylbenzothiazolin-2-one hydrazone with aromatic amines was applied to the determination of seven pharmaceutical sulphonamides containing a primary aromatic amino group. A mixture of an acidic solution of the sulphonamide and the chromogenic reagent was treated with ammonium iron(III) sulphate. The wavelengths of maximum absorption are from 565 to 620 nm and the molar absorptivities range from 2.18 × 103 to 6.32 × 103 l mol–1 cm–1. A linear correlation was found between absorbance at λmax. and concentration. The procedures developed for bulk sulpha drugs and some of their dosage forms are rapid, accurate, precise and comparable to the Bratton-Marshall procedure. The method is also applicable to blood and urine samples.