Collaborative study of a semiautomated method for the analysis of prednisolone and prednisone tablets

A semiautomated colorimetric method for the determination of prednisolone and prednisone was collaboratively studied by 6 collaborators. In the method, an alcoholic solution of the drug is extracted with chloroform and the extract is reacted with tetramethylammonium hydroxide and blue tetrazolium; the absorbance of the resulting color is read at 525 nm. Collaborators were supplied with 4 composites of tablets of different dosage levels, 2 containing prednisolone and 2 containing prednisone. Results agreed with those obtained by the author using the USP total steroid assay method. The coefficients of variation of the individual collaborator's results for prednisolone and prednisone ranged from 0.54 to 2.38 and from 0.34 to 2.19%, respectively. This method has been adopted as official first action.