What fixation and section thickness are recommended for Rhodanine staining?

• A. 10% NBF; paraffin 6-8 μm
• B. Formalin; 4-5 μm
• C. Alcohol; 2-3 μm
• D. Bouin's; 8-10 μm

Answer: (A)

Rhodanine staining relies on preserving copper deposits in the tissue and allowing the stain to penetrate evenly. Fixation with 10% neutral buffered formalin stabilizes tissue morphology without introducing artifacts that could mimic or mask copper. Embedding in paraffin and cutting sections 6–8 μm thick provides enough tissue for a clear color reaction while still letting the dye reach copper deposits. Other fixatives like Bouin's can introduce pigments or alter staining; alcohol fixation can dehydrate and shrink tissue, affecting copper localization; too thin or too thick sections can lead to inconsistent staining. Therefore, the recommended combination is 10% neutral buffered formalin fixation with paraffin sections cut at 6–8 μm.