Ehrlich's reagent or Ehrlich reagent is a reagent that contains p-dimethylaminobenzaldehyde (DMAB) and thus can act as an indicator to presumptively identify indoles and urobilinogen. Several Ehrlich tests use the reagent in a medical test; some are drug tests and others contribute to diagnosis of various diseases or adverse drug reactions. A very common Ehrlich test is a simple spot test to identify possible psychoactive compounds such as tryptamines (e.g. DMT) and ergoloids (e.g. LSD). The reagent will also give a positive result for opium, despite the opiates not containing the indole functional group, because of the presence of tryptophan in natural opium. It is named after Nobel Prize winner Paul Ehrlich who used it to distinguish typhoid from simple diarrhoea.
The reagent is prepared by dissolving 0.5–2.0 g of p–dimethylaminobenzaldehyde (DMAB) in 50 mL of 95% ethanol and 50 mL of concentrated hydrochloric acid and is best used when fresh. Other alcohols, such as 1-propanol, can also be used as well.
The Ehrlich reagent is similar to a number of other indole tests:
- The van Urk reagent, which uses DMAB, sulfuric acid and an oxidant.
- The Renz and Loew reagent, which uses p-dimethylaminocinnamaldehyde and may also be used for the detection of flavonoids.
- The "improved hallucinogen reagent", which uses a 1:1 solution of 5% DMAB in concentrated phosphoric acid (specific gravity 1.75) to methanol.
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- O’Neal, Carol L; Crouch, Dennis J; Fatah, Alim A (April 2000). "Validation of twelve chemical spot tests for the detection of drugs of abuse". Forensic Science International. 109 (3): 189–201. doi:10.1016/S0379-0738(99)00235-2. PMID 10725655.
- "Color Test Reagents/Kits for Preliminary Identification of Drugs of Abuse" (PDF). Law Enforcement and Corrections Standards and Testing Program. July 2000. Retrieved 2011-07-24.
- 02 July 2014. "Ehrlich's Reagent Safety Data Sheet" (PDF). Labchem. Retrieved 11 January 2015.
- Ehmann, A. (1977). "The van URK-Salkowski reagent — a sensitive and specific chromogenic reagent for silica gel thin-layer chromatographic detection and identification of indole derivatives" (PDF). Journal of Chromatography A. 132 (2): 267–276. doi:10.1016/S0021-9673(00)89300-0.
- Maunder, M. J. de Faubert (August 1974). "A field test for hallucinogens: further improvements". Journal of Pharmacy and Pharmacology. 26 (8): 637–638. doi:10.1111/j.2042-7158.1974.tb10677.x.
- Kovar, Karl-Artur; Laudszun, Martina (February 1989). "Chemistry and Reaction Mechanisms of Rapid Tests for Drugs of Abuse and Precursors Chemicals" (PDF). UNODC. p. 15. Retrieved 3 January 2016.