Mona M. Bedair

Spectrophotometric and polarographic determination of enalapril and lisinopril using 2,4-dinitrofluorobenzene

The reaction of enalapril maleate and lisinopril with 2,4-dinitrofluorobenzene has been used to form colored products and polarographically active derivatives. The different experimental conditions have been optimized. The proposed methods have been validated and applied to the determination of both drugs in their commercial tablets. The results have been statistically compared with those obtained using the official HPLC methods.

Colorimetric Determination of Seven Nonsteroidal Antiinflammatory Drugs Using 2-Nitrophenylhydrazine Hydrochloride

Abstract A simple, sensitive and convenient colorimetric method for the determination of seven nonsteroidal anti-inflammatory drugs, namely, flufenamic acid, mefenamic acid, niflumic acid, ketoprofen, ibuprofen, diclofenac sodium and indomethacin, was developed. The method is based on reaction of the abovementioned compounds - being carboxilic compounds, reacting with 2-nitrophenylhydrazine in presence of diclohexylcarbodiimide in ethanolic medium to give acid hydrazine, which showed intense violet colour with a maximum absorption at around 550 nm. The effect of reagent concentration (2-nitrophenylhydrazine hydrochloride, pyridine and dicyclohexylcarbodiimide), heating temperature and heating time were studied to optimize reaction conditions. The method was successfully applied to the determination of those drugs in pure and dosage forms, with a relative standard deviation less than 2%.

Computer-assisted spectrophotometry: multicomponent analysis with a discrete fourier transform.

A computer-assisted method for analysis of multicomponent mixtures by use of conventional absorbance as well as discrete Fourier transforin coefficients (combined trigonometric functions) is presented. The program can store absorbance data (A vs. lambda), process data by convolution with combined trigonometric functions, apply least-squares analysis and solve the resultant simultaneous linear equations, and display data on screen, printer or plotter.

Derivative spectrophotometric determination of glibenclamide, mebeverine hydrochloride and clopamide in the presence of their alkaline-induced degradation products

First- and second-derivative spectrophotometric methods have been proposed for the determination of glibenclamide, mebeverine hydrochloride and clopamide with their corresponding degradation products. Solutions of these drugs were analysed by measuring the first- and second-derivative spectral response at certain wavelengths where the respective degradation products exhibit no contribution. Also, clopamide can be determined in a mixture with reserpine and dihydroergocristine by utilising the second-derivative method. Kinetic investigation of the alkaline degradation rate of these drugs revealed that the proposed methods were stability indicating. The different pharmaceutical preparations were assayed and were found to give results of the same accuracy and reproducibility as the corresponding official method or “maximum absorbance” methods of assay.

The utilization of copper(II) phosphate for the anodic stripping voltammetric assay of alendronate sodium, desferrioxamine mesylate and lisinopril.

A sensitive differential pulse anodic stripping voltammetric method is described for the determination of alendronate sodium, desferrioxamine mesylate and lisinopril. The procedure is based on the formation of labile drug-copper(II) complex when shaking with copper(II) phosphate suspension. The voltammetric peaks, which correspond to the reduction of the copper(II) moiety of the formed complexes are obtained at -153, -74 and -111 mV, respectively. The different experimental parameters have been carefully studied. The method has been fully validated. The limit of detection was as low as 8.6 ng ml(-1). The method has been applied successfully for the determination of the drugs in plasma and in their pharmaceutical preparations. The obtained results were compared statistically with those obtained from a published method, in case of AS, or the official USP methods, for the other two drugs.

Spectrofluorimetric determination of guanethidine sulphate, guanoxan sulphate and amiloride hydrochloride in tablets and in biological fluids using 9,10-phenanthraquinone.

A highly sensitive spectrofluorimetric method for the determination of some drugs of the monosubstituted guanidine derivatives in laboratory made tablets, in spiked human serum and in urine samples is presented. The method is based on the reaction of guanethidine sulphate (I), guanoxan sulphate (II) and amiloride hydrochloride (III) with 9,10-phenanthraquinone (IV) to give highly fluorescent derivatives. The linearity ranges were found to be 0.06-0.96 mug/ml for (I) and (II) and 0.04-0.28 mug/ml for (III), with relative standard deviation less than 2%. Mean percentage recoveries for tablets were found to be 99.9 +/- 1.3, 100.5 +/- 1.1 and 100.0 +/- 1.6 for I, II and III, respectively. For I and III the results are highly correlated with the B.P. methods. Using the synchronous fluorimetry, differentiation between I and II was possible. Chloroform, dichloromethane and ethyl acetate have been used to extract I, II and III, respectively from serum and urine at basic pH, followed by applying the proposed fluorimetric method. Percentage recoveries were found to be 95.7-102.2%. The limit of detection is 0.04 mug/ml for I and II and 0.02 mug/ml for III.

Colorimetric Determination of Mebeverine Hydrochloride in Tablets by Charge

AbstractThree simple, rapid and sensitive colorimetric methods for the assay of mebeverine hydrochloride are described. The first method is based on the reaction of mebeverine with iodine to give a yellow molecular charge transfer complex in chloroform with a maximum absorbance at 292nm. The other two methods depend on the formation of radical anions between mebeverine hydrochloride and tetracyanoethylene (TCNE) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile with absorbance maxima at 416, 840 nm, respectively. Beers law was obeyed for the proposed methods, the apparent molar absorptivities were calculated to be 1.42×105, 1.46×104 and 1.59×104 respectively. The proposed methods have been applied for the assay of mebeverine hydrochloride in commercial tablets.

Spectrofluorimetric determination of three pharmaceutical thiocompounds and allopurinol using mercurochrome

Abstract A new, simple and sensitive fluorimetric method for the determination of three pharmaceutical thiocompounds: cimetidine, thiabendazole and carbimazole, and also allopurinol, has been presented. The method is based on the fluorescence quenching of mercurochrome (MER) in an aqueous alkaline medium. Calibration graphs correlating the fluorescence difference (Fo-F) or the fluoresence ratio (Fo/F) of MER before (Fo) and after (F) quencher addition versus the concentration of the latter are linear. Such linearity permitted the successful application of

Colorimetric determination of some penicillins and cephalosporins with 2-nitrophenylhydrazine hydrochloride.

A simple and sensitive calorimetric method for the determination of some penicillins and cephalosporins is presented. The method is based on reaction with 2-nitrophenylhydrazine hydrochloride in presence of dicyclohexylcarbodi-imide and pyridine. The violet colour of the resulting acid hydrazide is measured at the appropriate wavelength. The method has been applied to determination of these antibiotics in bulk and dosage forms, with a coefficient of variation less than 2%.

Analysis of Diphenhydramine Hydrochloride and Naphazoline Hydrochloride in Presence of Methylene Blue in Eye Drops by Second Derivative Spectrophotometry

AbstractA second (D2) derivative spectrophotometric technique has been applied for the determination of diphenhydramine hydrochloride in mixture with naphazoline hydrochloride and in presence of Methylene blue. Diphenhydramine hydrochloride has been extracted with chloroform and D2-value was measured at 255 nm. Naphazoline hydrochloride in the mixture has been determined by direct measurement of its D2 at 273 nm. Methylene blue could be determined in the mixture by direct absorbance measurement at 663 nm. As illustrate example, commercial eye drops was analysed for these two drugs in presence of methylene blue in pharmaceutical preparation. The results obtained were of high accuracy and good reproducibility.