The determination of phenothiazine drugs in pharmaceutical preparations by a difference spectrophotometric method

Abstract

A method is described for the rapid determination of phenothiazine drugs in a wide variety of pharmaceutical preparations. The drugs are determined by a difference spectrophotometric technique based upon the absorbance of the sulphoxide derivative of the drug relative to the absorbance of a solution of the underivatized drug. The sulphoxide derivatives are formed rapidly and quantitatively at room temperature by the addition of a solution of peroxyacetic acid, prepared by the slow reaction of hydrogen peroxide and glacial acetic acid on standing. The difference absorbance of the solutions is proportional to the concentration of the phenothiazine drug in the preparation and is specific for the intact drug in the presence of oxidative and photochemical decomposition products, colouring and flavouring agents, excipients and most co-formulated drugs.

Differential pulse cathodic voltammetric determination of floctafenine and metopimazine

“…FFN in Idarac-D ® tablets was assayed spectrophotometrically through the reaction with pchloranilic acid and measuring the 1 D of the product at 375 nm [7]. MPZ in Vogalene ® syrup was assayed using a difference spectrophotometric technique based on measuring the A at 358 nm after the addition of a solution of hydrogen peroxide and glacial acetic acid [18,19]. Applying the Student's t-and the variance ratio F-tests, the calculated values did not exceed the theoretical ones at P = 0.05, demonstrating that the proposed method is as accurate and precise as the reference spectrophotometric methods.…”

Difference spectrophotometric assay of nitrazepam in tablet formulations

“…The advantages of difference spectrophotometry, which is a modified spectrophotometric technique for the selective analysis of certain drugs in the presence of absorbing substances that interfere in a direct spectrophotometric assay, have been amply demonstrated (eg Doyle & Fazzari 1974;Davidson 1976Davidson , 1982Davidson , 1984aDavidson , 1987. The basis of a difference spectrophotometric assay is that an absorbance difference (AA) is measured between two equimolar solutions of the absorbing analyte in the presence of different reagents that reproducibly alter the spectral properties of the analyte.…”

Spectrophotometric Assay of Prothipendyl through the Determination of Its Sulfoxide

“…However, the real great importance of difference spectrophotometry is in quantitative analysis as a consequence of its potential to increase the selectivity of the measurement(16).The aim of this research is to develop a new and simple method for prothipendyl hydrochloride determination. It seems promising to carry out the analysis of prothipendyl hydrochloride in the form of the corresponding stable S-oxide, which is easily obtained in a slightly acidic medium using aliphatic diperoxyacids or inorganic Caro peroxoacid(10,15,17,18).in water and a water-ethanol solution 1:1 (v/v) respectively. All other used chemicals were analytical grade.…”