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.

Determination of ethinyloestradiol in the presence of norethisterone by derivative-difference spectrophotometry

A simple and direct method for the determination of ethinyloestradiol as a minor component in the presence of norethisterone and in oral contraceptive tablets is presented. The method is based on measuring the signal intensity, d delta A/d lambda and d2 delta A/d lambda 2, of the generated first and second derivative spectra of the delta-absorbance curves obtained by measuring solutions in methanol and methanol-sodium hydroxide at certain wavelengths. The method has been applied to the determination of ethinyloestradiol in oral contraceptive tablets, with a coefficient of variation of less than 2%.

Derivative Spectrophotometric Determination of Some Corticosteroids in Combinations with Other Drugs

Three 2-component mixtures, namely, dexamefhazone-chlorpheniramine maleate, prednisolone-chlorpheniramine maleate, and prednisolone-salicylic acid, have been assayed using their first (D1,) and second (D2) derivative spectra in methanol, delta absorption (ΔA), and second derivative of Δ A (Δ D2) spectra in methanol-methanolic HC1. In the first 2 mixtures, chlorpheniramine maleate was determined by measuring its Δ D2 value at 278 nm, while dexamethazone and prednisolone were analyzed by measuring their D1 values at 248 nm. Prednisolone and salicylic acid were analyzed in combination by using their respective D2 spectral responses at 272 and 314 nm. The results obtained are reasonably reproducible with a relative standard deviation <2%. The method has been successfully applied to the analysis of these drugs in their pharmaceutical formulations.

Spectrophotometric Determination of Captopril and Penicillamine through the Use of Ligand Exchange Complexation Reactions

Two spectrophotmetric methods based on combined redox - ligand exchange reactions were developed for the determination of captopril and penicillamine in pure form and in their dosage forms. The first method is based on attenuating the absorbance of a ternary complex: silver (I) - bromopyrogallol red - phenanthroline in a buffer solution of pH6-8. The method has the concentration ranges 2-10 μg mL(-1) and 0.5-1.75 μg mL(-1) for captopril and penicillamine respectively, and the detection limits 7.1 × 10(-2) and 5.7 × 10(-2) μg mL(-1) for captopril and penicillamine respectively. The second method is based on decreasing the absorbance of a chloroformic solution of copper (II) - oxine chelate when shaken with the drug solution in buffer medium of pH 8. The drugs were determined in the concentrations 30-90 μg mL(-1) and 30-100 μg mL(-1) for captopril and penicillamine respectively, and the detection limits 0.94 and 1.76 μg mL(-1) for captopril and penicillamine respectively. The proposed methods were applied in the analysis of both compounds in their pharmaceutical preparations, and results were favorably compared with reference spectrophotometric methods regarding accuracy and precision.