ANALYTICAL APPLICATION OF REACTIONS OF 2-DISUBSTITUTED AND 10-DISUBSTITUTED PHENOTHIAZINES WITH SOME OXIDIZING-AGENTS

Phenothiazines substituted in the 2 and 10 positions exhibit many valu able analytical properties due to their characteristic structure (the presence of chemically active sulphur, nitrogen and substituents). The y are easily oxidized in an acidic medium by some oxidizing agents wit h the formation of coloured products. This property has been exploited in volumetric and spectrophotometric analysis. Phenothiazines have be en used as reversible redox indicators in the titrations of some reduc ing agents and as reagents for the spectrophotometric determinations. The influence of iodide, nitrite, vanadium and iron ions on the oxidat ion of phenothiazines by means potassium bromate and hydrogen peroxide was used for the development of kinetic spectrophotometric methods. I t was found that several spectrophotometric methods of the determinati on of phenothiazines are based on the formation of coloured oxidation products. Various oxidants recommended for the spectrophotometric dete rmination of phenothiazines are described in the present paper. The pa per is divided into six parts. The first chapter presents the structur es of the coloured products of 2,10-disubstituted phenothiazines and t he mechanism of their formation. Chapters 2 and 3 are devoted to the a pplication of the phenothiazines as indicators and reagents in chemica l analysis. Chapter 4 shows the catalytic influence of trace amounts o f some ions on the oxidation of phenothiazines by means potassium brom ate and hydrogen peroxide. Chapter 5 is devoted to the application of various oxidants for the determination of phenothiazines and main conc lusions are drawn in Chapter 6. The paper is based on the chemical lit erature up to 1996.