Sudan III

Technical Specifications

Product Description & Scientific Applications

Sudan III (C.I. Solvent Red 23; C.I. 26100; Cerasin Red; 1-{[4-(phenyldiazenyl)phenyl]diazenyl}naphthalen-2-ol) is a disazo (bis-azo) lysochrome — a fat-soluble dye built on a phenylazo–phenylazo–naphthol skeleton whose two consecutive azo (–N=N–) linkages form the extended chromophore, giving an absorption maximum near 507 nm (solvent-dependent) and a red-orange colour. It stains by physical partitioning — far more soluble in lipids and organic solvents (chloroform, benzene, acetone, toluene; only slightly in ethanol) than in water or the alcoholic staining solution, so it concentrates in lipid-rich phases and leaves aqueous compartments unstained. Sudan III is one of the foundational histological lipid stains, an oil-soluble industrial colorant, and an analytical reference standard in food-adulteration testing.

Common Scientific Applications

• Histological lipid staining: A classical lysochrome for neutral lipids — chiefly triglycerides, and to a lesser extent fatty acids — on fresh or frozen (cryostat) sections, since routine paraffin processing dissolves them. It shows fat droplets in adipocytes and the sudanophilic breakdown products of degenerating myelin, viewed by conventional light microscopy over a haematoxylin nuclear counterstain.
• Teaching and reference stain: Oil Red O gives a deeper red and has largely replaced Sudan III for routine fat staining; Sudan III has a more orange shade, remains a classical demonstration of the lysochrome principle, and serves as a simple bench indicator for fats and oils. It is a brightfield absorption stain — fluorescent lipid detection instead uses dyes such as Nile Red or BODIPY.
• Cell and plant microscopy: Stains stored-oil bodies and lipid droplets in plant and cultured animal cells, and colours cutinised (cuticle) and suberised (cork, Casparian strip) cell walls red-orange.
• Solvent dye and colorant: As the solvent dye Solvent Red 23, it colours non-polar substrates — mineral oils and petroleum/hydrocarbon products, waxes, greases, fats, plastics and acrylic emulsions.
• Food-adulteration reference standard: Sudan dyes are not authorised as food colorants and are characterised by EFSA as potentially genotoxic and carcinogenic, yet have been used illegally to deepen the colour of chilli powder, palm oil and spices; Sudan III is a target analyte and reference standard for HPLC, LC-MS/MS and immunoassay (ELISA) screening — with emerging aptamer-based (ELONA) assays — of Sudan I–IV in food-safety testing.
• Oil-phase and multiphase-flow tracer: Sudan III, the parent molecule of the family and used with the more common Sudan IV and Oil Red O, stains and tracks non-aqueous-phase liquids (NAPLs) in porous-media flow experiments, including subsurface-contamination studies, exploiting selective partitioning into the organic phase and strong visible absorption.

Shipping Destinations

• EU & UK: Priority delivery, 2–5 business days.
• United States (DDP): 3–7 business days, duties and taxes prepaid.
• EFTA Countries (DDP): 3–7 business days, duties and taxes prepaid.
• Worldwide: 7–14 business days, selected locations.