M. Rizk

Differential pulse polarographic determination of ofloxacin in pharmaceuticals and biological fluids

A sensitive method is described for the determination of ofloxacin in its pure form, dosage forms and biological fluids. The proposed method depends upon the polarographic activity of ofloxacin in Britton Robinson buffers, whereby a well-defined cathodic wave is produced over the pH range 4.1-10.3. The wave was characterized as being irreversible, diffusion-controlled with limited adsorption properties. The current-concentration relationship was found to be rectilinear over the range 5x10(-5)-5x10(-4) M and 1x10(-5)-5x10(-4) M using the DC(t) and DPP modes respectively, with a minimum detectability (S/N=3) of 3x10(-7) M. The proposed method was successfully applied to the determination of ofloxacin in tablets and biological fluids. The results obtained were found to be in agreement with those obtained by a reference method.

Europium(III) ion probe spectrofluorometric determination of diclofenac sodium

A new method has been devised for the determination of diclofenac sodium in bulk and in pharmaceutical preparations using Eu3+ ions as the Fluorescent probe. The technique was built around the hypersensitive property of the transitions of the fluorescent probe ion, Eu3+, at 616 nm. This is normally a forbidden transition, but the interaction with diclofenac sodium, which contains a carboxylic group, makes the transition allowed and enhances the intensity of its fluorescence emission. The Eu3+ fluorescence emission at 592 nm comes from a non-hypersensitive transition and is not affected by ligation. The intensity ratio, R, defined as I592/I616, was used as a measure of the percentage of bound probe ions. Diclofenac and Eu(III) forms a (1:1) molar complex. The relative stability constant of the complex was found to be 10(5). A linear relationship between bound Eu3+ and the concentration of diclofenac sodium was found for concentrations from 10 to 200 micrograms ml-1, with a recovery percentage of 100.22 +/- 2.27. The method shows a good agreement with a spectrophotometric method.

Estimation of the ionization pKa of pharmaceutical substances using the computer program Sparc

The computer program sparc was used to calculate the pK(a) values of some important pharmaceutical substances. The sparc models proved to be suitable for estimating the pK(a) values of beta-adrenergic blocking agents and benzodiazepine drugs. Ionization macroconstants, microconstants, zwitterionic equilibria, speciation curves as a function of the pH and the isoelectric points of a semi-essential amino acid, arginine, and an anti-inflammatory, niflumic acid, were calculated.

Fluorimetric determination of aminoglycoside antibiotics using lanthanide probe ion spectroscopy.

The application of probe ion fluorimetry has succeeded in the microdetermination of six aminoglycoside antibiotics: neomycin, streptomycin, gentamicin, tobramycin, amikacin and kanamycin as sulfate salts in pure form and in some pharmaceutical preparations. The method is based on the reaction of Eu(3+) ions with aminoglycosides through amino and hydroxy groups. Such interactions enhance the intensity of the 616 nm fluorescence emission of the Eu(3+) ion. The fluorescence at 592 nm comes from a non-hypersensitive transition and is not affected by the ligand which is bound to the probe ions. The intensity ratio R, defined as I (592)I (616) was used to determine the amount of free and bound europium ions. A linear relationship between bound europium ions and aminoglycoside was found within the concentration ranges 20-100 ppm for neomycin, 5-60 ppm for streptomycin, and 10-70 ppm for gentamicin, tobramycin, amikacin, and kanamycin as sulfate salts. The percentage recoveries ranged from 99.22 to 101.07, with standard deviations ranging from +/- 1.5 to +/- 4.38. The relative stability constants ranged from 5 x 10(3) to 2 x 10(4). The optimum reaction conditions were studied and the results obtained compared favourably with the fluorimetric method using fluorescmine reagent.

Voltammetric analysis of certain 4-quinolones in pharmaceuticals and biological fluids

The voltammetric behaviour of Enrofloxacin (I), Sparfloxacin (II) and Fleroxacin (III) was studied using direct current (DCt), differential pulse (DPP) and alternating current (ACt). All the drugs manifest cathodic waves in Britton Robinson buffer over the pH range of 4.0-11.98. The waves were characterized as being irreversible, diffusion-controlled with limited adsorption properties. The diffusion current concentration relationships were found to be rectilinear over the ranges 4 x 10(-5) x 10(-4) M, 1 x 10(-5)-2 x 10(-4) M, 1 x 10(-5)-4 x 10(-4) M using DCt mode for I, II and III, respectively and 1 x 10(-6)-4 x 10(-5) M, 1 x 10(-6)-1 x 10(-4) M, and 2 x 10(-6)-8 x 10(-5) M, using DPP mode for I, II and III respectively, with minimum detectability (S/N = 3) of 1 x 10(-7) M for I, II and 2 x 10(-7) M for III. The proposed method was successfully applied to the determination of the studied compounds either per se or in formulations and biological fluids. The results obtained were concordant to those given using reference methods.

Determination of phenothiazines by charge-transfer complex formation with chloranilic acid

A rapid and sensitive spectrophotometrc method has been developed for the microdetermination of some phenothiazine derivatives as the pure substances and in different dosage forms. The method depends on the formation of stable donor-acceptor complexes between phenothiazines and chloranilic acid in an acetonitrile-2-propanol solvent mixture. The resulting intensely purple chloranilic acid radical anion possesses a characteristic absorption maximum at 515 nm. Beers law is obeyed over the concentration ranges 1-6, 1-10 and 5-30 mug ml for prochlorperazine dimaleate, trifluoperazine dihydrochloride and thiethylperazine dihydrochloride, with apparent molar absorptivities of 7.76 x 10(4), 1.95 x 10(4) and 6.64 x 10(3) 1. mole(-1).cm(-1), respectively. Statistical comparison of the results with those of an official method shows excellent agreement and indicates no significant difference in precision.

Evaluation of Certain Pharmaceuticals with Dibromohydantion. V. Determination of Penicillins

Abstract A new bromometric assay procedure for penicillins was developed, using an organic brominating agent. 1,3-Dibromo, 5,5-dimethylhydantion (DBH). The experimental conditions, the molar ratio as well as the identification of the reaction products were thoroughly studied. The end point could be detected visually or potentiometrically. Spectrophotometric titration could also be performed. The suggested procedure could be successfully applied to pharmaceutical preparations containing penicillins. The percentage recoveries for different penicillins were satisfactory.

Voltammetric analysis of trazodone HCl in pharmaceuticals and biological fluids.

The voltammetric behavior of trazodone (TRZ) HCl was studied using direct current (DC(t)), differential pulse (DPP) and alternating current (AC(t)) polarography. The drug manifests cathodic waves over the pH range of 10-14. The waves were characterized as being irreversible, diffusion-controlled with limited adsorption properties. At pH 10, the diffusion current-concentration relationship was found to be rectilinear over the range 4-32 and 0.8-24 microg ml(-1) using DC(t) and DPP modes, respectively, with minimum detectability (S/N=2) of 0.104 microg ml(-1) (2.45 x 10(-6) M) and 0.314 microg ml(-1) (7.397 x 10(-6) M) using the DPP and DC(t) modes, respectively. The diffusion-current constant (I(d)) is 4.31+/-0.02 (n=6). The proposed method was successfully applied to the determination of the studied compound either in pure form or in formulations. The results obtained were favorably compared with those given using a reference method. Furthermore, the proposed method was applied to the determination of TRZ in spiked human urine and plasma adopting the DPP technique. No prior extraction step is needed in case of urine. The percentage recoveries were 98.43+/-0.79 and 97.44+/-0.705 (n=4) in spiked human urine and plasma, respectively. A pathway for the electrode reaction was postulated.

Direct current polarographic determination of chlorprothixene and thiothixene after bromination

Abstract A direct current (dc) polarographic method is described for the determination of chlorprothixene and thiothixene after reaction with bromine. The bromo derivatives of the two drugs show a well-defined, diffusion-controlled cathodic wave; the height of the latter increases with an increase in the concentration of the depolarizers. The different experimental conditions were carefully studied and incorporated into the procedure. The proposed method was further applied to the studied compounds in dosage forms and the results obtained were compared favorably to those given by compendial methods.

Tetracyanoethylene in pharmaceutical analysis. Part I. A spectrophotometric method for the determination of some pharmaceutically important hydrazine and pyrazolone derivatives

A simple and sensitive spectrophotometric method is described for the determination of some hydrazine and pyrazolone derivatives. The determination is based on the formation of charge-transfer complexes between tetracyanoethylene as a π-acceptor and the studied drugs as n-donors in acetonitrile solvent. The spectra, various experimental parameters and the stoicheiometry and stability of the reaction products were studied. The complexes formed were found to absorb at 395, 380, 410, 420 and 440 nm for the complexes formed with phenelzine sulphate, isonicotinic acid hydrazide, hydralazine hydrochloride, amidopyrine and antipyrine, respectively. Beers law is obeyed in the concentration ranges 20–80, 1–10, 2–40, 10–60 and 30–80 µg ml–1, respectively, for the studied drugs. The proposed method is simple and can be applied to the determination of the studied drugs in their pharmaceutical dosage forms.