Which hematoxylin solution must be used within a few days after preparation?

• A. Harris
• B. Gill's
• C. Weigert's
• D. Mallory's

Answer: (C)

Hematoxylin solutions rely on a specific chemical form (hematein) complexed with a mordant to stain nuclei. Some formulations are meant to be used soon after preparation because their active components oxidize or degrade quickly, affecting staining reliability. Weigert's hematoxylin is an iron-hematoxylin solution that’s best used fresh; its staining quality can deteriorate within days as the reagents change with time, leading to inconsistent nuclear staining. For that reason, it is standard to prepare it and use it within a few days of preparation. Other hematoxylins like Harris, Gill's, and Mallory's are typically stored or aged to develop the desired color and can be used over a longer period once prepared, whereas Weigert's needs that immediate-use window.