Sudan IV
chemical compound
Sudan IV (C24H20N4O) 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.
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 alcohol, 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.
Sudan I, Sudan III, and Sudan IV have been classified as category 3 carcinogen by the International Agency for Research on Cancer.
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.
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Datasets, specimens, observations and peer-reviewed methods provide the appropriate test for the technical claims summarized here. The source revision retrieved here is dated Aug 15, 2026. The linked authority identifier is Q3291758. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Sudan IV” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.