What is the Best Procedure to Remove Formalin Pigment from Formaldehyde-Acetic Acid-Alcohol Fixed Tissues?

There has been some disagreement as to whether formalin pigment is bleached by potassium permanganate/oxalic acid (PPO). This study analyzed the bleaching characteristics of PPO on tissues fixed in formaldehyde-acetic acid-alcohol and compared PPO with other bleaching agents and conventional formalin pigment removal methods. It was found that PPO removed formalin pigment. Other bleaching methods (hydrogen peroxide, periodic and chromic acids) also removed the pigment to some extent. Garvey's pigment removal procedure was more effective than alcoholic picric acid for the routine removal of formaldehyde-acetic acid-alcohol associated formalin pigment. (The J Histotechnol 33(3):109-111, 2010)