Which fixative contains sodium phosphate di- and monobasic?

• A. Zamboni
• B. Orth
• C. Zenker
• D. B-5

Answer: (A)

Buffering with sodium phosphate di- and monobasic helps keep a fixative’s pH near neutral during tissue fixation, which preserves morphology more reliably and reduces acid-related artifacts. Zamboni fixative is a formaldehyde-based fixative that includes this phosphate buffering system, providing stable pH and better preservation of fine cellular detail and antigenicity. That buffering feature is what makes it distinct from the other fixatives listed, which rely on different chemical components (such as mercuric salts, picric acid, or acetic acid) and do not use the sodium phosphate di- and monobasic buffering system.