The Porter-Silber reaction utilizes which reagent to detect corticosteroids?

The Porter-Silber reaction is specifically designed to detect the presence of corticosteroids by utilizing phenylhydrazine as the reagent. In this reaction, phenylhydrazine reacts with the ketone group present in corticosteroids to form a colored hydrazone product. The intensity of the color produced can be measured spectrophotometrically, allowing for the quantification of corticosteroids in a sample. This method is sensitive and specific to corticosteroids, making it a valuable tool in clinical laboratories for assessing adrenal function and diagnosing various conditions related to corticosteroid levels.

The other options are not used in the Porter-Silber reaction; phosphoric acid, acetic anhydride, and sodium acetate do not participate in the specific reaction that detects corticosteroids in the way phenylhydrazine does.