Analysis of steroids. Part XXI. A spectrophotometric method for the determination of 21-amino corticosteroids

Abstract

A method is described for determining 21-amino corticosteroids that involves their oxidation with mercury(II)-EDTA complex and condensation of the resulting 20-keto-21-aldehyde with 4,5-dimethyl-O-phenylenediamine to form the quinoxaline derivative; the latter is then determined spectrophotometrically in a strongly acidic medium at wavelength 351 nm. The molar extinction coefficient (12 500) is high enough for the method to be sufficiently sensitive.

As 21-hydroxy corticosteroids do not react with the mercury(II)-EDTA complex, the method is highly specific for amino corticosteroids, and has proved suitable for the determination of 21-amino corticosteroids in various pharmaceutical formulations. The coefficients of variation range between 1 and 3 per cent.