Sudan IV

Sudan IV (C24H20N4O) is a lysochrome (fat-soluble dye) diazo dye used for 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.

Sudan IV is one of the dyes used for Sudan staining. Similar dyes include Oil Red O, Sudan III, and Sudan Black B. Staining is an important biochemical technique, offering the ability to visually qualify the presence of the fatty compound of interest without isolating it. For staining purposes Sudan IV can be made up in propylene glycol. Alternatively, authors have reported using the dye saturated in isopropyl acohol, 95% ethanol, or 0.05% by weight in acetone:ethanol:water (50:35:15). The idea is to use a moderately apolar solvent to solubilize the dye allowing it to partition into the highly apolar fat without the solvent solubilizing the fat to be stained.

Its risk and safety phrases are / and.

Sudan IV is also known as Sudan R, C.I. Solvent Red 24, C.I. 26105, Lipid Crimson, Oil Red, Oil Red BB, Fat Red B, Oil Red IV, Scarlet Red, Scarlet Red N.F, Scarlet Red Scharlach, and Scarlet R. In its purified form it is called Biebrich scarlet R, which should not be confused with the water-soluble Biebrich scarlet.

In industry, it is used to color nonpolar substances like oils, fats, waxes, greases, various hydrocarbon products, and acrylic emulsions. Sudan IV is also used in United Kingdom as a fuel dye to dye lower-taxed heating oil; because of that it is also known as Oil Tax Red. As a food dye, Sudan IV is considered an illegal dye, mainly because of its harmful effect over a long period of time, as it is a carcinogenic It was ruled unsafe in the 1995 food safety regulations report.