TETRAZOLIUM ASSAY OF STEROIDS
A number of steroids essentially having a α-ketol (21-hydroxy-20 keto) side-chain group, for instance : hydrocortisone, hvdrocortisone acetate, prednisolone, methylprednisolone, methylprednisolone acetate, flucocinolone acetonide, triamcionolone acetonide and the like—are quantitatively reduced by tetrazolium salts to their respective coloured formazan derivatives. Thus, it is possible to carry out the assay of a number of formulations that contain corticosteroids by using triphenyltetrazolium chloride. The said reaction is usually performed in an alkaline medium (tetramethylammonium hydroxide) between a temperature ranging between 30° to 35°C for a duration of 1 to 2 hours. The absorbance of the resulting formazan derivative producing a red product is usually measured around 484 nm.