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Eosin Yellow Sodium Salt
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Eosin Yellow Sodium Salt (Eosin Y)
Biological Staining Dye — H&E Counterstain & Cytoplasm Visualization | CAS 17372-87-1
Cat. No. ASD-607 Eosin Y | CI 45380 C₂₀H₆Br₄Na₂O₅ MW 691.86 g/mol ~99% Dye Content 🇦🇺 Made in Melbourne ⚡ Same-Week Dispatch
Overview & Biochemistry
Eosin Yellow Sodium Salt (Eosin Y) is an anionic xanthene dye and the universal counterstain in the Haematoxylin and Eosin (H&E) technique — the most widely performed staining procedure in diagnostic histopathology and biological research. As an anionic (negatively charged) dye, Eosin Y binds selectively to positively charged (basic/cationic) cellular components, staining cytoplasm, extracellular matrix, collagen fibres, and red blood cells in shades of pink to red, providing the critical contrast against the blue-purple nuclear staining produced by haematoxylin.
The sodium salt form (Eosin Y, disodium salt) offers superior water solubility compared to the free acid form (Eosin B), making it the preferred grade for aqueous and alcoholic staining solutions used in routine laboratory workflows.
Mode of Action
Anionic Dye → Electrostatic Binding → Cytoplasmic & ECM Staining
Eosin Y carries a net negative charge (anionic) in aqueous solution due to its brominated xanthene structure and sodium salt dissociation. It binds electrostatically to positively charged amino groups on proteins — particularly abundant in cytoplasmic proteins, muscle fibres, collagen, and erythrocytes. The interaction is reinforced by hydrophobic bonding between the dye's aromatic rings and protein side chains. Unlike nuclear staining with haematoxylin, eosin binding does not require a mordant — it proceeds directly via ionic attraction, producing the characteristic pink-to-red coloration that defines the "E" component of H&E.
Eosin Y carries a net negative charge (anionic) in aqueous solution due to its brominated xanthene structure and sodium salt dissociation. It binds electrostatically to positively charged amino groups on proteins — particularly abundant in cytoplasmic proteins, muscle fibres, collagen, and erythrocytes. The interaction is reinforced by hydrophobic bonding between the dye's aromatic rings and protein side chains. Unlike nuclear staining with haematoxylin, eosin binding does not require a mordant — it proceeds directly via ionic attraction, producing the characteristic pink-to-red coloration that defines the "E" component of H&E.
Applications
🔬
H&E Staining
Primary counterstain — cytoplasm & ECM
🧬
Cytology
Papanicolaou & cytoplasm visualization
🧠
Histopathology
Tissue architecture & diagnosis
📈
Haematology
Erythrocyte & blood smear staining
🧮
Fluorescence
Photoconversion & STED microscopy
🏫
Education
Teaching labs & demonstrations
H&E Staining Protocol — Eosin Counterstain Step
| 1 | Prepare Eosin Y solution: Dissolve 1 g Eosin Y (ASD-607) in 100 mL distilled water (1% aqueous stock). For alcoholic eosin, dissolve in 80% ethanol. Add 0.5 mL glacial acetic acid per 100 mL to intensify staining and sharpen differentiation. |
| 2 | After haematoxylin: Ensure sections have been stained with haematoxylin, differentiated in acid-alcohol, and blued in running tap water. Sections should be purple-blue at this stage. |
| 3 | Apply eosin: Flood slides with Eosin Y solution. Stain for 1–5 minutes depending on desired intensity. Longer times produce deeper pink cytoplasm and more vivid red blood cell staining. |
| 4 | Rinse: Rinse briefly in distilled water or 70% ethanol. Avoid prolonged washing — eosin is water-soluble and will decolourise with excess rinsing. |
| 5 | Dehydrate & clear: Pass through graded alcohols (70% → 95% → 100% ×2) then clear in xylene ×2. Mount with DPX or equivalent permanent mountant. |
| 6 | Result: Nuclei — blue-purple (haematoxylin). Cytoplasm, muscle, collagen — pink to red (eosin). Erythrocytes — bright red/orange. Keratin — deep orange-red. |
⚠️ Note: Eosin staining intensity is highly sensitive to rinsing time, alcohol concentration, and acetic acid content. Optimise for your specific tissue type, fixation method, and coverslipping medium. Alcoholic eosin generally produces crisper differentiation than aqueous formulations.
Eosin Y vs Eosin B — Comparison
| Property | Eosin Y (ASD-607) | Eosin B |
|---|---|---|
| CAS | 17372-87-1 (Na salt) | 548-24-3 |
| Colour | Bright pink / rose | Bluish-red / crimson |
| Water solubility | High (preferred) | Moderate |
| Routine H&E use | Universal standard | Occasional specialist use |
| Cytoplasm staining | Pink-red | Darker red-crimson |
| λmax | ~516 nm | ~514 nm |
Cross-Reference / Equivalent Products
| Manufacturer | Product Name | Cat. No. | Notes |
|---|---|---|---|
| Sigma-Aldrich (Merck) | Eosin Y, disodium salt | E4009 | Equivalent powder grade |
| Merck Millipore | Eosin yellowish for microscopy (Certistain®) | 1.15935 | Equivalent powder grade |
| Thermo Fisher Scientific | Eosin Y Solution, Alcoholic | E3857 | Ready-to-use solution; ASD-607 is powder |
| Atom Scientific | Eosin Y Sodium Salt | BIEY10 | Equivalent powder grade |
Cross-references are for convenience only. Catalogue numbers are trademarks of their respective owners.
Related Products
Chemical & Physical Properties
| Product Name | Eosin Yellow Sodium Salt (Eosin Y) |
| Catalogue Number | ASD-607 |
| Synonyms | Eosin Y; Eosin Yellowish; Acid Red 87; CI 45380; Tetrabromofluorescein disodium salt |
| CAS Number | 17372-87-1 |
| Colour Index | CI 45380 |
| Molecular Formula | C₂₀H₆Br₄Na₂O₅ |
| Molecular Weight | 691.86 g/mol |
| Grade | Biological Stain Grade |
| Appearance | Red to orange crystalline powder |
| Dye Content | ~99% |
| Solubility (water) | ~400 g/L at 25°C (freely soluble) |
| Solubility (ethanol) | Soluble (~20 g/L in 95% ethanol) |
| λmax (aqueous) | ~516 nm |
| Charge | Anionic (negatively charged at physiological pH) |
| Melting Point | >300°C (with decomposition) |
Working Solution Preparation
| Formulation | Concentration | Solvent | Application |
|---|---|---|---|
| Aqueous Eosin Y | 0.5–1.0% w/v | Distilled water | Routine H&E, general histology |
| Alcoholic Eosin Y | 0.5–1.0% w/v | 70–80% ethanol | Crisper differentiation; cytology |
| Acidified Eosin | 1.0% w/v + 0.5% AcOH | 80% ethanol | Enhanced intensity; sharper contrast |
| Phloxine-Eosin | 0.5% Eosin + 0.1% Phloxine B | 80% ethanol | Enhanced cytoplasm contrast |
Quality Control Specifications
| Test Parameter | Specification |
|---|---|
| Appearance | Red to orange crystalline powder; free-flowing |
| Dye Content | ~99% (CI 45380 titration) |
| λmax | 516 ± 3 nm (0.01% aqueous solution) |
| Staining Performance | Clear pink-red cytoplasmic staining; sharp contrast vs haematoxylin-stained nuclei |
| Solubility | Complete dissolution in distilled water at 10 mg/mL |
| Heavy Metals | ≤20 ppm (ICP-OES) |
Storage & Stability
| Storage Temperature | 15–25°C (ambient, away from heat sources) |
| Container | Tightly sealed, light-resistant container |
| Protect From | Direct light, moisture, and strong oxidising agents |
| Shelf Life (powder) | 3 years from manufacture date when stored correctly |
| Working Solutions | Aqueous solutions stable 6–12 months at RT; alcoholic solutions stable 12–24 months. Filter if precipitate forms. |
Literature & References
| # | Reference |
|---|---|
| 1 | Bancroft JD, Gamble M (eds). Theory and Practice of Histological Techniques. 6th ed. Churchill Livingstone; 2008. [Standard H&E protocol and eosin formulations] |
| 2 | Kiernan JA. Histological and Histochemical Methods: Theory and Practice. 4th ed. Scion Publishing; 2008. [Eosin binding mechanism and differentiation] |
| 3 | Fischer AH, Jacobson KA, Rose J, Zeller R. Hematoxylin and eosin staining of tissue and cell monolayers. Cold Spring Harb Protoc. 2008;(5):pdb.prot4986. [Standard H&E protocol reference] |
| 4 | Titford M, Horenstein MG. Histochemical staining in the era of immunohistochemistry. Am J Clin Pathol. 2005;123(suppl):S56–S68. [Ongoing relevance of eosin in modern pathology] |
| 5 | Minamikawa T, Kawano S, Ishitobi H, et al. Eosin Y as a photosensitizer. J Biomed Opt. 2016;21(4):046001. [Fluorescence and photoconversion applications] |
📄 Full SDS available: Download the complete 16-section GHS Safety Data Sheet (Australian WHS Regulations 2023 / GHS 7th Edition) — contact support@ausamics.com.au
Section 1 — Identification
| Product Name | Eosin Yellow Sodium Salt (Eosin Y) |
| Catalogue No. | ASD-607 |
| Supplier | AuSaMicS Pty Ltd | ABN 56 676 640 467 |
| Address | 31 Longview CT, Thomastown VIC 3074, Australia |
| Emergency | Poisons Information Centre: 13 11 26 (24 hr, Australia) |
| Phone | +61 412 520 598 |
| support@ausamics.com.au |
Section 2 — Hazard Identification (GHS 7th Ed / WHS 2023)
| GHS Classification | Eye Irrit. 2 — H319: Causes serious eye irritation Not classified as acutely toxic by oral, dermal, or inhalation routes at laboratory use concentrations |
| Signal Word | WARNING |
| GHS Pictograms | ⚠️ Exclamation mark |
| Additional Note | Stains skin, clothing, and surfaces pink/red — use appropriate PPE. Staining is not a hazard but is persistent. |
Sections 4–8 — First Aid, Fire & PPE
| Inhalation | Remove to fresh air. Seek medical attention if symptoms persist. |
| Skin Contact | Wash with soap and water. Note: pink staining of skin is expected and harmless; fades within 24–48 hr. Use nitrile gloves to prevent staining. |
| Eye Contact | Irrigate with large amounts of water ≥15 min, hold eyelids apart. Seek immediate medical attention if irritation persists. |
| Ingestion | Rinse mouth with water. Not expected to be acutely toxic at laboratory amounts. Call Poisons Centre 13 11 26 if large amounts ingested. |
| Extinguishing Media | Water spray, foam, dry powder, CO₂ |
| Respiratory Protection | P1 particulate filter if dust generated during weighing |
| Eye Protection | Safety glasses — staining of eyes/face is a practical risk |
| Skin Protection | Nitrile gloves, lab coat. Eosin Y stains skin and fabric permanently. |
Sections 12–15 — Ecology, Disposal & Regulatory
| Aquatic Toxicity | Limited data; avoid discharge to waterways as a precaution. |
| Disposal | Dispose per local EPA regulations. Small quantities may be diluted and discharged to sewer in accordance with local trade waste regulations. |
| Transport | Not classified as dangerous goods — ADG Code, IMDG, IATA |
| Regulatory Framework | Australian WHS Regulations 2023 | GHS 7th Edition | Safe Work Australia COP 2021 |
| AICIS Status | Listed on Australian Inventory of Industrial Chemicals (AIIC) |
| Poisons Schedule | Not scheduled under SUSMP |
Quality Specifications
| Parameter | Specification | Method |
|---|---|---|
| Appearance | Red to orange crystalline powder; free-flowing | Visual |
| Dye Content | ~99% (CI 45380) | Dye content titration |
| λmax | 516 ± 3 nm | UV-Vis spectrophotometry |
| Staining Performance | Clear pink-red cytoplasmic staining; sharp contrast vs haematoxylin nuclei | Functional H&E staining test |
| Solubility | Complete dissolution in distilled water at 10 mg/mL | Visual inspection |
| Heavy Metals | ≤20 ppm | ICP-OES |
| Batch COA | Available for every production lot | On request or download |
Manufacturing & Documentation
Manufactured by AuSaMicS Pty Ltd
31 Longview CT, Thomastown VIC 3074, Australia | ABN 56 676 640 467
✓ Batch-level quality control on every lot
✓ Full GHS-compliant documentation (COA, TDS, SDS)
✓ Australian stock — no import delays, no customs holdups
✓ Technical support direct from our formulation team
31 Longview CT, Thomastown VIC 3074, Australia | ABN 56 676 640 467
✓ Batch-level quality control on every lot
✓ Full GHS-compliant documentation (COA, TDS, SDS)
✓ Australian stock — no import delays, no customs holdups
✓ Technical support direct from our formulation team
Available Documentation
| 📄 Certificate of Analysis (COA) | Batch-specific | Available on request |
| 📋 Technical Data Sheet (TDS) | Full specifications and preparation notes |
| ⚠️ Safety Data Sheet (SDS) | GHS 7th Ed | WHS 2023 compliant | 16 sections |
⚠️ Intended Use: For laboratory and research use only. Not for diagnostic, clinical, therapeutic, human, veterinary, or environmental treatment use.