Ponceau 4R (Acid Red 18) is a synthetic strawberry red azo dye that is a food colorant dye used in a variety of food products. It is stable to light, heat and acid, but fades in the presence of ascorbic acid. It is usually synthesized from aromatic hydrocarbons.

Tissue Staining:
1. prepare a staining solution for Ponceau 4R (usually in water or an appropriate buffer at a concentration of 0.1%-1%).
2. for staining of tissue sections or certain biological samples, after which the stain is rinsed with an appropriate solution to remove background staining.
3. protein electrophoresis or immunoblotting experiments: under certain circumstances, Ponceau 4R may be used as a dye to detect protein bands, but is less commonly used for routine immunoblotting (WB) because its azo dye properties may interfere with certain experimental analyses."