Abdel Fattah M. El Walily

Spectrophotometric and spectrofluorimetric estimation of ciprofloxacin and norfloxacin by ternary complex formation with eosin and palladium(II)

Spectrophotometric and spectrofluorimetric methods for the determination of two broad-spectrum fluoroquinolone antibacterials (ciprofloxacin and norfloxacin), either in pure form or in tablets, are described. Both methods are based on the formation of a ternary complex between palladium(II), eosin and the fluoroquinolone in the presence of methyl cellulose, as surfactant. Spectrophotometrically, under the optimum conditions, the ternary complexes showed an absorption maximum at 545 nm, with apparent molar absorptivities of 3.4 x 10(4) and 2.7 x 10(4) 1 mol-1 cm-1 and Sandells sensitivities of 1.01 x 10(-2) and 1.12 x 10(-2) micrograms cm-2 for ciprofloxacin and norfloxacin, respectively. The solution of the ternary complex obeyed Beers law in the concentration range 3-10 micrograms ml-1 for both quinolones. The proposed method was applied to the determination of the two drugs in pharmaceutical tablets. A fluorescence quenching method for the determination of both quinolones by forming this ternary complex was also investigated for the purpose of enhancing the sensitivity of the determination. The results obtained by the application of both procedures and the USP XXIII methods were in good agreement and statistical comparison by means of Students t-test and the variance ratio F-test showed no significant differences between the three methods.

Simultaneous determination of enalapril maleate and hydrochlorothiazide by first-derivative ultraviolet spectrophotometry and high-performance liquid chromatography

Two methods are described for the simultaneous determination of enalapril maleate and hydrochlorothiazide in combined pharmaceutical tablets. The first method depends on first-derivative ultraviolet spectrophotometry, with zero-crossing and peak-to-base measurement methods. The first-derivative amplitudes at 224 and 260 nm were selected for the assay of enalapril maleate and hydrochlorothiazide, respectively. The second method is based on high-performance liquid chromatography on a reversed-phase column using a mobile phase of acetonitrile-water (20:80, v/v) (pH 3.8) with programmable detection at 215 and 275 nm. Both methods showed good linearity, precision and reproducibility. The proposed methods were successfully applied to the determination of these drugs in laboratory-prepared mixtures and in commercial tablets.

Application of first-derivative UV-spectrophotometry, TLC-densitometry and liquid chromatography for the simultaneous determination of mebeverine hydrochloride and sulpiride

Three methods are described for the simultaneous determination of mebeverine hydrochloride (MB) and sulpiride (SU) in combined pharmaceutical tablets. The first method depends on first-derivative ultraviolet spectrophotometry, with zero-crossing measurement method. The first derivative amplitudes at 214.2 and 221.6 nm were selected for the assay of MB and SU, respectively. Calibration graphs follow Beers law in the range of 10-30 and 2-8 microg/ml(-1), and the linearity was satisfactory (r = 0.9999), for MB and SU, respectively. The second method was based on the application of the thin layer chromatographic separation of both drugs followed by the densitometric measurements of their spot areas. After separation on silica gel GF254 plates, using ethanol: diethyl ether: triethylamine (70:30:1 v/v) as the mobile phase, the chromatographic zones corresponding to the spots of MB and SU were scanned at 262 and 240 nm, respectively. The calibration function was established in the ranges of 4-12 microg for MB and 2-8 microg for SU. The third method was an internal standard procedure based on high performance liquid chromatographic separation of the two drugs on a reversed-phase, Bondapak CN column. The detection was done at 243 nm using buclizine hydrochloride as internal standard. All chromatographic methods showed good linearity, precision and reproducibility. No spectral or chromatographic interference from the tablet excipients were found. The proposed methods were successfully applied to the assay of commercial tablets and content uniformity test. The procedures were rapid, simple and suitable for quality control application.

Use of Cerium (IV) in the Spectrophotometric and Spectrofluorimetric Determinations of Penicillins and Cephalosporins in Their Pharmaceutical Preparations

Abstract Spectrophotometric and spectrofluorimetric procedures for the quantitative determination of four penicillins [Amoxycillin (AMX), Bacampicillin (BAC), Piperacillin (PPN) and Sultamcillin (SULT)] and ten cephalosporins [Cefadroxil (CDL), Cefamandole nafate (MAN), Cefuroxime axetil or sodium (CFX), Cefaclor (CFCR), Ceftazidime (CZD), Ceftizoxime (CTIZ), Ceftriaxone (CTRX), Cefoperazone (CPZ), Cefixime (CXIM) and Cefpodoxime proxetil (CFPD)] are described. Both methods are based on the acidic oxidation of the antibiotics with cerium (IV) at elevated temperature. The effect of the reagent concentration, volume of the acid,and the heating temperature were studied to optimize the reaction conditions. Each antibiotic was determined by either measuring the absorbance difference at 317 nm or the cerous inherent fluorescence at 256 and 356 nm for excitation and emission wavelengths, respectively. The two procedures have been successfully applied to the assay of these antibiotics in their pharmaceutical dosage forms. The obtained results have been statistically compared with those obtained by the official methods.

Selective spectrofluorimetric determination of phenolic β-lactam antibiotics through the formation of their coumarin derivatives

A simple, sensitive and selective spectrofluorimetric procedure was developed for the determination of amoxycillin, cefadroxil and cefoperazone. The method is based on the reaction between these drugs and ethyl acetoacetate, in acidic medium, to give yellow fluorescent products with excitation wavelengths ranging from 401 to 467 nm and emission wavelengths ranging from 465 to 503 nm. The reaction conditions were studied and optimized. The reaction obeyed Beers law over the range of 10.0-20.0, 1.5-1.0 and 50.0-100.0 microg ml(-1) for amoxycillin, cefadroxil and cefoperazone, respectively. Interferences from other antibiotics, drugs and dosage forms additives, in capsules and vials dosage forms, were investigated. The proposed method was applied to the analysis of pharmaceutical formulations (capsules and vials) containing the above antibiotics, either alone or in combination with other antibiotics or drugs. The validity of the method was tested by the recovery studies of standard addition which were found to be satisfactory. The results of the proposed method demonstrated that the method is equally accurate, precise and reproducible as the official methods (USP XXIII) and those published for the non-official binary mixtures.

First-derivative spectrophotometric and LC determination of cefuroxime and cefadroxil in urine

Two methods are presented for the determination of cefuroxime and cefadroxil in human urine using first (1D) derivative spectrophotometry and high-performance liquid chromatography. Cefuroxime and cefadroxil were determined by measurement of their first-derivative amplitude in 0.1 N sodium hydroxide at 292.5 and 267.3 nm, respectively in the concentration range of 2-10 microg ml(-1) for each drug. The HPLC method depends upon using a LiChrospher 100 RP-18 (5 microm) column at ambient temperature for cefuroxime and 35 degrees C for cefadroxil with mobile phases consisting of water-acetonitrile-acetic acid (85:15:0.1 v/v) at a flow rate of 1.5 ml min(-1) for cefuroxime; and 0.02 M potassium dihydrogen phosphate-acetonitrile (95:5 v/v) containing 0.003% (w/v) hexanesulphonic acid sodium salt and adjusted to apparent pH 3 with phosphoric acid at a flow rate of 2 ml min(-1) for cefadroxil. Quantitation was achieved with UV detection at 275 and 260 nm for cefuroxime and cefadroxil, respectively, based on peak area with linear calibration curves at the concentration ranges of 2-10 microg ml(-1) for cefuroxime and 5-20 microg ml(-1) for cefadroxil. The proposed methods were applied to the determination of dissolution rate for tablets and capsules containing each drug. The urinary excretion patterns as the cumulative amounts excreted have been calculated for each drug using the proposed methods.

Spectrophotometric Determination of Etilefrine, Ritodrine, Isoxsuprine and Salbutamol by Nitration and Subsequent Meisenheimer Complex Formation

Abstract A simple and sensitive colorimetric method has been developed for the determination of four phenolic drugs, namely, etilefrine hydrochloride, ritodrine hydrochloride, isoxsuprine hydrochloride and salbutamol sulphate. The method is, mainly, based on the nitration of the drug molecule followed by the subsequent formation of meisenheimer complex with a nucleophilic reagent (acetone) in alkaline medium. The experimental conditions leading to optimum chromogen intensity and stability were carefully studied and incorporated in the general procedure. Under the proposed conditions, the method was applicable over the concentration range of 4.8–16 μg ml−1 for the four drugs. The suggested method was further applied for the determination of the studied drugs in bulk and pharmaceutical dosage forms. The results of the analysis were found to agree statistically with those obtained with either the official or the referee methods. The procedure is characterized by its simplicity with accuracy and precision.

Spectrophotometric determination of some phenolic sympathomimetic drugs through reaction with 2,6-dihaloquinone chlorimides

A spectrophotometric procedure is described for the determination of three phenolic sympathomimetic drugs: etilefrine hydrochloride, prenalterol hydrochloride and ritodrine hydrochloride. The method involves the use of 2,6-dichloro- and 2,6-dibromoquinone chlorimides as chromogenic reagents. The phenolic drugs produce a blue color, peaking from 610 to 630 nm. The colors produced obey Beers law and are suitable for the quantitative determination of the named compounds. The molar ratios of the reactions were established and a proposal for the reaction pathway is given. The procedures described were applied successfully to the determination of the compounds in their dosage forms. The results showed that the proposed procedures compared favourably with the reference methods and satisfactory sensitivity, accuracy and precision (SD < 0.1 μg ml−1) were noted. Detection limits are typically 0.2–0.4 μg ml−1. Other advantages of the procedures are their simplicity and speed.

Analysis of nifedipine acebutolol hydrochloride binary combination in tablets using UV-derivative spectroscopy, capillary gas chromatography and high performance liquid chromatography

Three methods are described for the simultaneous determination of nifedipine and acebutolol hydrochloride in combined pharmaceutical tablets. The first method depends on first-derivative ultraviolet spectrophotometry, with peak-to-base and zero-crossing measurements methods. The first derivative amplitudes at 400 and 352 nm were selected for the assay of nifedipine and acebutolol hydrochloride, respectively. Calibration graphs follow Beers law in the range of 4-12 and 44-132 micrograms ml-1 and the linearity was satisfactory (r = 0.999) for nifedipine and acebutolol hydrochloride, respectively. The second method was based on the separation of nifedipine from acebutolol hydrochloride, with an internal standard thymolphthalein, using capillary gas-liquid chromatography with a programmable temperature change. The third method was based on high performance liquid chromatographic separation of the two drugs on a reversed-phase, C18, column using a mobile phase of methanol-water (55:45, pH 4.5) with a programmable flow rate of 1 ml min-1 for 4 min which changed to 2 ml min-1 for the rest of the run. The detection was done at 260 nm using oxprenolol hydrochloride as an internal standard. Both chromatographic methods showed good linearity, precision and reproducibility. No spectral or chromatographic interference from the tablet excipients were found. The proposed methods were successfully applied to the assay of commercial tablets and a content uniformity test. The procedures were rapid, simple nondestructive and suitable for quality control application.

Spectrophotometric determination of flunarizine dihydrochloride through the formation of charge-transfer complex with iodine

A spectrophotometric method is described for the assay of flunarizine dihydrochloride. The method is based on the molecular interaction between the drug and iodine, to form a charge-transfer complex in which the drug acts as n-donor and iodine as sigma-acceptor. The iodine was found to form charge-transfer complex in a 1:1 stoichiometry with absorption bands at 295 and 355 nm. The concentrations were linear over 8-13 micrograms ml-1 at both 295 and 355 nm, respectively. A complete, detailed investigation of the formed complex was made with respect to its composition, associated constant and free energy change. The method has been applied successfully to the analysis of commercially available flunarizine dihydrochloride capsules without interference from the capsules excipient. To validate the proposed method, its accuracy and precision, the results were statistically compared with a newly developed reversed-phase HPLC procedure using Student-t and F-ratio tests.