Related Experiment Video
Updated: Aug 11, 2026

Facile Preparation of 4-Substituted Quinazoline Derivatives
Published on: February 15, 2016
The determination of sulphoxide in degraded phenothiazine formulations by difference spectrophotometry
Abstract:
A method is described for the assay of phenothiazine sulphoxides which may be formed in phenothiazine formulations during storage under unfavourable conditions. The assay is based upon the measurement of difference absorbance of the sulphoxide solution in 0.2 M hydrochloric acid relative to an equimolar solution reduced with zinc dust. A solvent extraction procedure avoids interference from colouring agents and coloured photolytic breakdown products of the phenothiazines. The assay is specific in the presence of intact drug, sulphone and co-formulated drugs for the formulations examined and is sensitive to 0.5% of the total phenothiazine present as sulphoxide. Many aqueous formulations stored in partially filled containers have been shown to contain up to 31.5% of the total phenothiazine as sulphoxide.
More Related Videos
Related Concept Videos
Preparation and Reactions of Sulfides
Spectrophotometry: Introduction
The essential components of a spectrophotometer include a source of electromagnetic radiation, a slot for placing a material to be analyzed, and a...
Precipitation Titration: Endpoint Detection Methods
In the Volhard method, a standard excess of AgNO3 is first added to the...

