What fixative is used with Alcian blue pH 2.5?

• A. 10% NBF, Bouin
• B. Neutral buffered formalin
• C. Bouin’s solution alone
• D. Formalin-fixed, paraffin-embedded

Answer: (A)

Alcian blue staining at pH 2.5 highlights acidic mucins by binding to sulfated and carboxylated glycosaminoglycans, so the fixative chosen must preserve those mucins without extracting them while keeping tissue architecture intact. Bouin’s fixative is especially good at preserving mucins, which gives strong, crisp Alcian blue pH 2.5 staining. In many protocols, a combination of 10% neutral buffered formalin with Bouin’s solution is used to balance excellent mucin preservation with solid overall morphology. This mix tends to yield reliable acid mucin staining and good tissue detail. Neutral buffered formalin alone can be less optimal for mucin preservation, Bouin’s solution alone can cause over-fixation or brittleness in some tissues, and formalin-fixed, paraffin-embedded describes a processing state rather than a fixative choice.