Hoda Mahgoub

Spectrophotometric determination of omeprazole, lansoprazole and pantoprazole in pharmaceutical formulations

The compensation method and other chemometric methods (derivative, orthogonal function and difference spectrophotometry) have been applied to the direct determination of omeprazole, lansoprazole and pantoprazole in their pharmaceutical preparations. The methods have been validated; the limits of detection were found to be 3.3x10(-2), 3.0x10(-2) and 3.5x10(-2) microgram ml(-1) for the three drugs, respectively. The repeatabililty of the methods were found to be 0.3-0.5%. The linearity ranges were found to be 0.5-3.5 microgram ml(-1). The proposed methods have been applied to the determination of the three drugs in their grastro-resistant formulations. The difference spectrophotometric (DeltaA) method is unaffected by the presence of acid induced degradation products; hence can be used as a stability indicating assay.

Spectrophotometric determination of binary mixtures of pseudoephedrine with some histamine H1-receptor antagonists using derivative ratio spectrum method

A derivative spectrophotometric method is developed for the assay of three binary mixtures of pseudoephedrine with fexofenadine (mix I), cetirizine (mix II) and loratadine (mix III). The method is based on the use of the first derivative of the ratio spectrum. The ratio spectrum was obtained by dividing the absorption spectrum of the mixture by that of one of the components. The concentration of the other component was determined from its respective calibration graph treated similarly. Moreover, the influence of Deltalambda for obtaining the first derivative of the ratio spectra and the effect of the divisor concentration on the calibration graphs were studied. The described method was applied for the determination of these combinations in synthetic mixtures and dosage forms. The results obtained were accurate and precise.

Spectrophotometric and titrimetric determination of nizatidine in capsules.

Four simple and accurate methods are described for the determination of nizatidine (NIZ) in pharmaceutical preparations. The first method is based on the formation of an ion-pair complex between the drug and either of bromocresol purple or picric acid with subsequent measurement of the developed colors at 411 and 400 nm, respectively. The second method depends on the condensation of mixed anhydrides of citric acid/acetic anhydride, with the tertiary amino group of the drug, where the developed color is measured spectrophotometrically at 545 nm. The oxidation of nizatidine by N-bromosuccinimide was utilized as a basis for the titrimetric method for its assay in capsules. The last method depends on the oxidation of nizatidine by ammonium cerium IV sulfate in the presence of perchloric acid with subsequent measurement of the absorbance at 314 nm; this principle is adopted to develop a kinetic method for the determination of NIZ in capsules. All the reaction conditions have been studied. The detection limits were varied from 0.44 to 0.78 microg ml(-1). The proposed methods were successfully applied to the assay of nizatidine in capsules.

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.

Non-parametric linear regression of discrete fourier transform convoluted chromatographic peak responses in non-ideal conditions

This manuscript discusses the application of chemometrics to the handling of HPLC response data using a model mixture containing ascorbic acid, paracetamol and guaiphenesin. Derivative treatment of chromatographic response data followed by convolution of the resulting derivative curves using 8-points sinx(i) polynomials (discrete Fourier functions) was found beneficial in eliminating different types of interferences. This was successfully applied to handle some of the most common chromatographic problems and non-ideal conditions, namely: very low analyte concentrations, overlapping chromatographic peaks and baseline drift. For example, a significant change in the correlation coefficient of guaiphenesin, in case of baseline drift, went from 0.9978 to 0.9998 on applying normal conventional peak area and first derivative under Fourier functions methods, respectively. It also compares the application of Theils method, a non-parametric regression method, in handling the response data, with the least squares parametric regression method, which is considered the de facto standard method used for regression. Theils method was found to be superior to the method of least squares as it assumes that errors could occur in both x- and y-directions and they might not be normally distributed. In addition, it could effectively circumvent any outlier data points.

Computerized Derivative Spectrophotometric Assay of two Component Mixture Using Least Squares Method

AbstractTwo computerized spectrophotometry methods; the derivatve (D-) method and the derivative under least squares approach (D-LS) method; have been described for the assay of two component mixture. That mixture has been solved for chlorpheniramine maleate (CP) and phenylephrine hydrochloride (PE) existing in a ratio range of 1/0.8 to 1/2. Being more versatile and fast, the proposed methods supersede the Vierordts method in dealing with the assay of two component mixture since the latter is subjective to many limitations.

Spectrofluorimetric assay of tetracycline and anhydrotetracycline in combination

Spectrofluorimetric methods are described for the assay of tetracycline (TC) and anhydrotetracycline (ATC) in combination, without prior separation. The interference from ATC in the TC assay has been corrected for by forming the aluminium complexes of both drugs and measuring the difference in fluorescence at 475 and 418 nm, with excitation at 393 nm. Similarly, measurement of the fluorescence of the magnesium complexes at 525 and 470 nm (excitation at 440 nm) nullifies TC interference in the ATC assay.

Voltammetric, spectrofluorimetric and spectrophotometric methods to determine flufenamic acid

Simple, rapid and sensitive voltammetric, spectrofluorimetric and spectrophotometric methods for determination of flufenamic acid (FF) in bulk powder and capsule dosage form are presented. The methods are based on the cyclisation reaction of FF with concentrated sulphuric acid to produce the corresponding acridone derivative. The voltammetric method is based on the adsorptive stripping differential pulse (DP) technique. The acridone derivative is determined over the concentration range of 8-60 ng ml(-1) using adsorptive preconcentration at the hanging mercury drop electrode (HMDE). The lower detection limit was found to be 1.02 ng ml(-1). The fluorimetric and spectrophotometric methods are based on the measurement of the fluorescence intensity at 450 nm (lambda(ex) = 400 nm)and peak-to-peak measurements of the first- (D1) and second-derivative (D2) curves, respectively. Beers law is obeyed over the concentration ranges of 2-20 ng ml(-1) and 0.2-8.0 microg ml(-1) for the fluorimetric and spectrophotometric measurements, respectively. The three methods were proved to be accurate and reproducible as indicated by a relative standard deviation of <2%.

Spectrophotometric and fluorimetric determination of aztreonam in bulk and dosage forms

Spectrophotometric and fluorimetric determination of aztreonam were achieved through its reaction with cerium (IV) in acidic medium. The spectrophotometric method involves the quantitation of the amount of ceric equivalent to aztreonam by measuring the absorbance at 317 nm and the corresponding first-derivative value at 284 nm for the blank solution against the reaction solution. Beers law is obeyed over the concentration ranges of 1.5-4 and 1-4 microg ml(-1), respectively. Meanwhile, in the fluorimetric method, higher sensitivity was achieved by measuring the fluorescence intensity of the formed cerium (III) at lambda(em)=357 nm (lambda(ex)=257 nm) within a concentration range 150-350 ng ml(-1). Study of the reaction conditions and reaction stoichiometry were presented. Interference from L-arginine, which is frequently co-formulated with aztreonam, was tested. The proposed procedures were applied successfully to the determination of aztreonam in pure form and in presence of arginine both in laboratory mixtures and commercial vials. The proposed methods are sensitive, accurate and precise as compared with the official USP 24 HPLC method.

Spectrophotometric Assay of Fluphenazine HCL-Nortriptyline HCL Mixture in Tablets Using Fourier Function Method

Abstract The Fourier function method has been applied to the independent determination of fluphenazine hydrochloride (FH) and nortriptyline hydrochloride (KH) (1:20) in both laboratory made mixtures and commercial tablets. The method is based on the absorbance measurement of FE (the minor component) in concentrated mixture solutions, which is then properly diluted prior to NH absorbance measure-