ASD-639
Indigo Carmine (E132) – Food Grade Colourant, CI 73015, CAS 860-22-0 | ASD-639
$27.00
AUD ex GST
Biological Stains & Dyes · C.I. 73015
Indigo Carmine (Indigotine, E 132)
Water-soluble indigoid dye for histological counterstaining, redox and alkaline pH indication, and E 132 colour reference work.
Cat. No. ASD-639CAS 860-22-0Dye content ≥ 85 %λmax ≈ 610 nmFood-grade E 132
Also known as: Indigotine, Acid Blue 74, CI Food Blue 1, FD&C Blue No. 2, indigo-5,5′-disulfonic acid disodium salt.
At a Glance
FormulaC₁₆H₈N₂Na₂O₈S₂
Mol. weight466.35 g/mol
AppearanceDark blue powder
Solubility (water)≈ 10 g/L, 25 °C
pH range11.6 blue → 14.0 yellow
Batch dye content90.72 %
Overview
Indigo carmine is the disodium salt of indigo-5,5′-disulfonic acid. Adding two sulfonate groups turns insoluble indigo into a water-soluble anionic dye with an intense blue colour and an absorption maximum near 610 nm.
The dye is valued in the laboratory for three properties. It binds collagen and cytoplasm as an acid dye. It changes colour reversibly on reduction and oxidation. It turns from blue to yellow in strongly alkaline solution.
For laboratory, research, education and quality-control use. Not intended for human or veterinary therapeutic use, diagnosis, or direct consumption. Food-grade (E 132) material. For food-industry supply, contact Ausamics for suitability and regulatory documentation.
How It Works
Oxidised form is blue. Reduced (leuco) form is yellow. In alkaline glucose solution the dye passes through red intermediates, then re-oxidises to blue when shaken with air.
Alkaline pH indicator
pH 11.6 · bluepH 14.0 · yellow
Key Applications
HistologyCounterstain in picro-indigo carmine methods, giving blue-green collagen against red or magenta nuclei.
Redox ChemistryRedox indicator: blue when oxidised, yellow in the reduced leuco form. Used in oxygen-sensitive reactions.
Alkaline pH IndicatorColour change from blue to yellow between pH 11.6 and 14.0 in strongly alkaline solutions.
EducationClassic glucose–indigo carmine “traffic light” demonstration of oxidation and reduction.
Food Colour QCReference material for E 132 identification, spectrophotometry and colour-matching work.
Microscopy & TracingWater-soluble blue dye for contrast, tracing and visualisation in research models.
Advantages & Considerations
Advantages
- High dye content: specification ≥ 85 %, current batch 90.72 %
- Meets the E 132 purity limits on the manufacturer's batch certificate
- Water-soluble and easy to prepare as aqueous stock
- Reversible colour change for redox teaching and testing
Considerations
- Light sensitive: store powder and solutions in the dark
- Fades in strong oxidants (e.g. hypochlorite) and reducing conditions
- Limited solubility (≈ 10 g/L); warm gently for stronger stocks
- Harmful if swallowed (H302); wear gloves when handling
Specification Summary
| Parameter | Specification |
|---|---|
| Physical appearance | Blue powder |
| Total dye content (dried basis, 105 ± 1 °C, 2 h) | Min. 85 % |
| Loss on drying at 135 °C, plus chlorides and sulfates (as sodium salts) | Max. 15 % |
| Water-insoluble matter | Max. 0.2 % |
| Combined ether extracts | Max. 0.2 % |
| Subsidiary dyes | Max. 1 % |
| Isatin sulfonic acid | Max. 0.5 % |
| Lead (Pb) | Max. 2 ppm |
| Arsenic (As) | Max. 3 ppm |
| Heavy metals | Max. 40 ppm |
Frequently Asked Questions
What is the difference between indigo carmine and indigo?
Indigo is insoluble in water. Indigo carmine is indigo with two sulfonate groups added, sold as the disodium salt, so it dissolves in water and works as an acid dye.
Is this the same as E 132 or FD&C Blue No. 2?
Yes. Indigo carmine, indigotine, E 132 and FD&C Blue No. 2 are names for the same colour. This batch meets the purity limits of the E 132 specification on the manufacturer's certificate.
How do I make a stock solution?
Dissolve 0.1–1.0 g in 100 mL of purified water to make a 0.1–1 % w/v solution. Solubility is about 10 g/L at 25 °C, so warm gently for stronger solutions. Store in an amber bottle and prepare fresh when colour intensity matters.
Why did my solution turn yellow?
Indigo carmine turns yellow in two cases: when it is reduced (for example by glucose in alkaline solution) and above about pH 12. Shaking a reduced solution with air restores the blue colour.
What dye content does this product have?
The specification is at least 85 % total dye content on a dried basis. The current batch tested at 90.72 %. A batch COA is available on request.
Technical Specifications
| Catalogue No. | ASD-639 |
| C.I. number | 73015 |
| CAS / EC | 860-22-0 / 212-728-8 |
| E number | E 132 |
| Formula | C₁₆H₈N₂Na₂O₈S₂ |
| Mol. weight | 466.35 g/mol |
| Dye content | Min. 85 % (dried basis) |
| λmax | ≈ 610 nm (water) |
| Storage | 15–25 °C, dry, dark, tightly closed |
| Documents | TDS, SDS; batch COA on request |
Applications
- Picro-indigo carmine counterstain
- Redox indicator
- Alkaline pH indicator
- Chemistry teaching demonstrations
- E 132 reference and QC
Stock Solution (1 % w/v)
- Weigh 1.0 g of indigo carmine.
- Add to about 80 mL of purified water.
- Stir, warming gently to 40–50 °C if needed, until dissolved.
- Make up to 100 mL with purified water.
- Filter if required. Store in an amber bottle at room temperature.
Storage & Stability
Store at 15–25 °C in a dry place, tightly closed and protected from light. Use before the expiry date on the label. Prepare working solutions fresh when colour intensity is critical.
Technical Data Sheet — Indigo Carmine
TDS-ASD-639 · Rev 1.0 · November 20261. Identification
| Chemical name | Disodium 3,3′-dioxo-2,2′-bi-indolylidene-5,5′-disulfonate |
| Synonyms | Indigotine; Indigo-5,5′-disulfonic acid disodium salt; Acid Blue 74; CI Food Blue 1; FD&C Blue No. 2 |
| C.I. number | 73015 |
| E number | E 132 |
| CAS number | 860-22-0 |
| EC number | 212-728-8 |
| Molecular formula | C₁₆H₈N₂Na₂O₈S₂ |
| Molecular weight | 466.35 g/mol |
| Dye class | Indigoid, anionic (acid) dye |
2. Intended Use
Histological counterstain, redox indicator, alkaline pH indicator, teaching reagent and E 132 reference colour. For laboratory, research, education and quality-control use. Not intended for human or veterinary therapeutic use, diagnosis, or direct consumption.
3. Mode of Action
The two sulfonate groups make the dye anionic, so it binds positively charged tissue proteins such as collagen in acidic stains. The central indigoid chromophore is reversibly reduced to a yellow leuco form, and above about pH 12 the dye shifts from blue to yellow.
4. Physical & Chemical Properties
| Appearance | Dark blue powder |
| Colour of aqueous solution | Blue |
| Absorption maximum (λmax) | approx. 610 nm in water |
| Solubility | Water: approx. 10 g/L at 25 °C; slightly soluble in ethanol |
| pH indicator range | pH 11.6 (blue) to 14.0 (yellow) |
| Redox behaviour | Reduced to a yellow leuco form; re-oxidised to blue by air |
| Light sensitivity | Light sensitive; protect solutions and powder from light |
5. Specifications
| Parameter | Specification |
|---|---|
| Physical appearance | Blue powder |
| Total dye content (dried basis, 105 ± 1 °C, 2 h) | Min. 85 % |
| Loss on drying at 135 °C, plus chlorides and sulfates (as sodium salts) | Max. 15 % |
| Water-insoluble matter | Max. 0.2 % |
| Combined ether extracts | Max. 0.2 % |
| Subsidiary dyes | Max. 1 % |
| Isatin sulfonic acid | Max. 0.5 % |
| Lead (Pb) | Max. 2 ppm |
| Arsenic (As) | Max. 3 ppm |
| Heavy metals | Max. 40 ppm |
6. Solution Preparation
Stock solution (1 % w/v): dissolve 1.0 g in about 80 mL purified water, warming gently if needed, and make up to 100 mL. Dilute for use according to your method. Store in amber glass.
7. Storage & Shelf Life
Powder: 15–25 °C, dry, tightly closed, protected from light. Use before the expiry date on the label.
8. References
- Commission Regulation (EU) No 231/2012, Annex: E 132 Indigotine, Indigo carmine. Specifications for food additives.
- FAO/WHO JECFA. Indigotine: Combined Compendium of Food Additive Specifications, Monograph 1.
- EFSA ANS Panel (2014). Scientific Opinion on the re-evaluation of indigo carmine (E 132) as a food additive. EFSA Journal 12(7):3768.
- Horobin R.W., Kiernan J.A. (eds) (2002). Conn's Biological Stains, 10th ed. BIOS Scientific Publishers, Oxford.
- Suvarna S.K., Layton C., Bancroft J.D. (eds) (2019). Bancroft's Theory and Practice of Histological Techniques, 8th ed. Elsevier.
Safety Data Summary — Indigo Carmine
SDS-ASD-639 · Rev 1.0 · November 2026 · Full 16-section SDS available on requestHazard Classification (GHS)
Signal word: Warning
Acute toxicity, oral, Category 4
H302 Harmful if swallowed.
Acute toxicity, oral, Category 4
H302 Harmful if swallowed.
Precautionary statements: P264 Wash hands thoroughly after handling. P270 Do not eat, drink or smoke when using this product. P301+P312 If swallowed: call a Poisons Information Centre or doctor if you feel unwell. P330 Rinse mouth. P501 Dispose of contents and container in accordance with local regulations.
Handling & Protection
- Avoid creating and breathing dust. Use with adequate ventilation.
- Wear nitrile gloves, laboratory coat and safety glasses.
- The dye stains skin and surfaces; clean spills promptly with water.
First Aid
- Inhalation: Move to fresh air.
- Skin: Wash with soap and water.
- Eyes: Rinse with water for several minutes. Seek medical advice if irritation persists.
- Ingestion: Rinse mouth. Call a Poisons Information Centre or doctor if you feel unwell.
Poisons Information Centre (Australia): 13 11 26 · Emergency: 000
Storage & Disposal
Store at 15–25 °C, dry, tightly closed and protected from light. Dispose of according to local regulations.
Transport
Not regulated as dangerous goods for road (ADG), sea (IMDG) or air (IATA) transport.
Quality & Certificate of Analysis
ASD-639 · Batch-specific COA available on requestEach batch is supplied with traceable manufacturer test data. A batch-specific Certificate of Analysis is available on request. Please quote the batch number printed on the label.
Typical Batch Results (Batch ZC30U)
| Test | Specification | Result |
|---|---|---|
| Physical appearance | Blue powder | Complies |
| Total dye content (dried basis, 105 ± 1 °C, 2 h) | Min. 85 % | 90.72 % |
| Loss on drying at 135 °C, plus chlorides and sulfates (as sodium salts) | Max. 15 % | 8.97 % |
| Water-insoluble matter | Max. 0.2 % | 0.109 % |
| Combined ether extracts | Max. 0.2 % | 0.098 % |
| Subsidiary dyes | Max. 1 % | < 1 % |
| Isatin sulfonic acid | Max. 0.5 % | < 0.5 % |
| Lead (Pb) | Max. 2 ppm | < 2 ppm |
| Arsenic (As) | Max. 3 ppm | < 3 ppm |
| Heavy metals | Max. 40 ppm | < 40 ppm |
Results as reported on the manufacturer's certificate for batch ZC30U. Manufactured 30/03/2026; expiry 29/03/2031.