Which staining method uses chromic acid as an oxidizing agent in its protocol?

• A. Bauer-Faulen stain
• B. Periodic acid-Schiff stain
• C. Hematoxylin and eosin stain
• D. Giemsa stain

Answer: (A)

Oxidation steps in staining protocols can create reactive sites that dyes bind to, producing specific color reactions. Chromic acid is a strong oxidizer used in certain stains to drive these reactions. This particular stain is defined by incorporating chromic acid into its protocol, giving it a distinct oxidative step that others in the list do not use. The periodic acid–Schiff method uses periodic acid as the oxidizer, not chromic acid. Hematoxylin and eosin relies on standard dye interactions with tissues rather than a chromic acid oxidation step, and Giemsa depends on dye chemistry and methanol fixation rather than chromic acid oxidation.