| Indigo carmine, or 5,5-indigodisulfonic acid sodium salt, also known as indigotine or FD&C Blue 2, is a pH indicator with the chemical formula C16H8N2Na2O8S2. It is approved for use as a food colorant in the United States[2] and in Europe.[3] and has the E number E132. Indigo carmine is commonly used as a pH indicator, often in a 0.2% aqueous solution. It is blue at pH 11.4 and yellow at 13.0. Indigo carmine is also a redox indicator, turning yellow upon reduction. Another use is as a dissolved ozone indicator[4] through the conversion to isatin-5-sulfonic acid.[4] This reaction has been shown not to be specific to ozone, however: it also detects superoxide, an important distinction in cell physiology.[5] Indigo carmine is also used as a dye in the manufacturing of capsules. In obstetric surgery, indigo carmine solutions are sometimes employed to detect amniotic fluid leaks. In urologic surgery, intravenous injection of indigo carmine is often used to highlight portions of the urinary tract. The dye is filtered rapidly by the kidneys from the blood, and colors the urine blue. This enables structures of the urinary tract to be seen in the surgical field, and demonstrate if there is a leak. However, the dye can cause a potentially dangerous increase in blood pressure in some cases.[6] Synonyms: Acid blue 74, C.I. 73015, 5,5-Indigodisulfonic Acid Disodium Salt, 2-(1,3-Dihydro-3-oxo-5-sulfo-2H-indol-2-ylidene)-2,3-dihydro-3-oxo-1H-Indole-5-sulfonic Acid, C.I. Acid Blue 74 (6CI), [delta2,2-Biindoline]-5,5-disulfonic Acid, 3,3-dioxo-, disodium Salt (8CI), 12070 Blue, 1311 Blue, 5,5-Indigodisulfonic Acid Disodium Salt, A.F. Blue No. 2, Acid Blue 74, Acid Blue W, Acid Leather Blue IC, Airedale Blue IN, Amacid Brilliant Blue, Aniline Carmine Powder, Ariavit Indigo Carmine, Atul Indigo Carmine, Basovit Blue 665E, Blue 2, Bucacid Indigotine B, C.I. 73015, C.I. 75781, C.I. Food Blue 1, C.I. Natural Blue 2, Canacert Indigo Carmine, Carmine Blue, Carmine indigo, Cilefa Blue R, Cogilor Blue 511.11, Disodium 5,5-Indigodisulfonate, Disodium 5,5-Indigotin Disulfonate, Dolkwal Indigo Carmine, E 132, Edicol Supra Blue X, Eurocert Indigo Carmine 311811, FD & C Blue 2, FD & C Blue No 2-307045, FD and C Blue 2, FD and C Blue No. 2, FD&C Blue No. 2, FD&C Blue No. 2-37006, Food Blue 1, Food Blue 2, Food Blue No. 1, Food Blue No. 2, Grape Blue A, HD Indigo Carmine, HD Indigo Carmine Supra, Hexacert Blue No. 2, Hexacol Indigo Carmine Supra, Indigo Carmine 307019, Indigo Carmine 36009, Indigo Carmine 37006, Indigo Carmine A, Indigo Carmine AC, Indigo Carmine BP, Indigo Carmine Conc. FQ, Indigo Carmine Powder, Indigo Carmine X, Indigo Extract, Indigo carmine, Indigo carmine 85E132, Indigo carmine NB, Indigotin, Indigotin (solubilized), Indigotine, Indigotine B, Indigotine Blue LZ, Indigotine Carmine, Indigotine Extra Pure A, Indigotine I, Indigotine IA, Indigotine Lake, Indigotine N, Indigotine disodium salt, Indocarmine F, Intense Blue, Japan Blue 2, Japan Food Blue No. 2, L Blue Z 5010, Maple Indigo Carmine, Mitsui Indigo Carmine, Necol Indigo Carmine, Neelicol Indigo Carmine, San-ei Indigo Carmine, Sepisperse Dry 1003, Sodium 5,5-indigodisulfonate, Sodium 5,5-indigotindisulfonate, Soluble indigo, Soluble indigo blue, Sumitomo Wool Blue SBC, Usacert Blue No. 2, Usacert FD & C Blue No 2-310118, Usacert FD and C Blue No. 2, WAS 35, Water Blue 177557, Water Blue 177558 CAS No: 860-22-0 Molecular Formula: C16H8N2Na2O8S2 Molecular Weight: 466.35 Appearance: Dark blue to purple powder Dye Content: 95% (dried basis) Heavy Metals: 40mg/Kg (as Pb) Arsenic (As): 0.0008% Lead (Pb): 0.001% UV Ratios: lambda max: 608nm (water) Visual Transition Range: pH 11.5 (Blue) to pH 14.0 (Yellow) Loss on Drying: 5% Solubility: Soluble in water (1g in 2ml at 25 C) Additional: Subsidiary dyes excluding disosdium 3,3-dioxo 2,2-bi- indolylidine-5,7 disulfonate: 1% Dye Intermediates: 0.50% Storage: Store at RT |
