Indole (Ehrich`s)

Indole (Ehrlich’s Reagent) is a classic chemical reagent containing p‑dimethylaminobenzaldehyde, widely used for detecting indole compounds such as tryptamine derivatives and urobilinogen.

🏭⚗️ Production
Ehrlich’s reagent is prepared by dissolving p‑dimethylaminobenzaldehyde (DMAB) in a mixture of ethanol (or other suitable alcohol) and concentrated hydrochloric acid. The freshly made solution is typically stored in a dark, tightly sealed container to maintain its sensitivity.

🔬 Properties
This reagent appears as a clear, pale-to-medium yellow liquid with acidic properties and excellent solubility in its alcohol-based solvent. Chemically, it reacts with the indole’s electron-rich position to form a colored complex, which can range in hue depending on the specific indole compound present.

🧪 Applications
Ehrlich’s reagent is commonly used in microbiology to detect indole-producing bacteria, particularly non-fermenters and anaerobes. When indole is present, it forms a red or pink ring at the interface after reaction, indicating a positive result. It is also used in clinical laboratories to detect urobilinogen in urine and in forensic or research settings for screening for tryptamine-based psychoactive substances.

⚠️ Safety
This reagent contains corrosive acid and alcohol, and should be handled with appropriate care. Use gloves and eye protection, and handle in a well-ventilated area. Store in a secure, tightly sealed container away from heat and direct light to preserve its reactivity.