A spectrofluorimetric determination of phenothiazine derivatives after their photooxidation or chemical or electrochemical oxidation in a flow injection arrangement
Abstrakt
A flow injection spectrofluorimetric determination of phenothiazine derivatives after their photo- or chemical or electrochemical oxidation has been developed. The determination in all the oxidation modes is based on the production of a colored phenothiazine radical-cation, which is spectrofluorimetrically detected.
A bench Hg ultraviolet lamp has been used for the photooxidation of the derivatives in a simple, laboratory-made photoreactor. For the chemical oxidation of the derivatives, two strong oxidants were tested, cerium(IV) sulfate and potassium permanganate (both in acidic media).
A better sensitivity has been attained with cerium(IV) ions. The electrochemical oxidation of the derivatives has been carried out continuously, in a laboratory-made thin-layer electrochemical flow-through cell.
The best sensitivity and the lowest detection limit (2.6 ng/mL of chlorpromazine) have been attained with photooxidation. On the other hand, the sample throughputs of flow-injection analysis are mutually comparable for chemical and electrochemical oxidation (60 samples per hour) and are higher than those for photooxidation (30 samples per hour).
The determination proposed has been used for determination of chlorpromazine and diethazine contents in medicinal preparations.