Ponceau S

Ponceau S, Acid Red 112, or C.I. 27195 is a sodium salt of a diazo dye that may be used to prepare a stain for rapid reversible detection of protein bands on nitrocellulose or PVDF membranes (Western blotting), as well as on cellulose acetate membranes. A Ponceau S stain is easily reversed with water washes, facilitating subsequent immunological detection. Common stain formulations include 0.1% (w/v) Ponceau S in 5% acetic acid or 2% (w/v) Ponceau S in 30% TCA and 30% sulfosalicylic acid.