Sudan IV is a lysochrome (fat-soluble dye) diazo dye used for the staining of lipids, triglycerides and lipoproteins on frozen paraffin sections. It has the appearance of reddish brown crystals with melting point 199 °C and maximum absorption at 520(357) nm.

Application

Sudan IV is lipophilic diazo dye, very similar to Sudan III. It is primarily used in Sudan IV staining method or in Churukian's variety of Lillie-Ashburn method in which it replaces Oil Red O. Those methods are used for staining lipids, triglycerides and lipoproteins on frozen histology sections.