Theory and practice of pharmacopoeial control of quality of drugs and excipients VIII. End-point indication and other conditions for the titration of primary aromatic amines in the European Pharmacopoeia (Ph. Eur.)


Authors: Jan Šubert ;  Jozef Kolář
Published in: Čes. slov. Farm., 2019; 68, 34-36
Category: Short Article

Overview

Indication of the equivalence point for the titration of primary aromatic amines (sulphonamides, etc.) with sodium nitrite solution according to Ph. Eur. (2.5.8) is performed electrometrically or using a prescribed indicator, the electrometric method not being specified. Better reproducibility of the assay results would add to Ph. Eur. the electrometric method to be used for the indication and suitable electrodes for it. The authors of the paper propose a potentiometric indication, which is in Ph. Eur. widely used. Further, they propose to consider whether in Article 2.5.8. Ph. Eur. indications using an indicator as an alternative to the instrumental indication required. The titration in the presence of hydrochloric acid favourably affects the addition of potassium bromide, cooling the solution prior to the titration prescribed by Ph. Eur. is not needed.

Keywords:

Ph. Eur. – titration of aromatic amines with sodium nitrite – endpoint indication – other conditions


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