Ehrlich's Reagent
Definition
A solution of para-dimethylaminobenzaldehyde in acid. It reacts with urobilinogen and related pyrrole-containing compounds to produce a pink-red colour, used as a chemical test for faecal material in forensic screening.
- Active reagent
- Para-dimethylaminobenzaldehyde in acid
- Target compound
- Urobilinogen and pyrrole compounds
- Positive colour
- Pink-red
- Application
- Presumptive faecal stain screening
Common questions
Why is urobilinogen a useful marker for faecal material specifically?+
Urobilinogen is a breakdown product of bile pigment produced by gut bacteria and is characteristically concentrated in faeces, so its presence supports faecal origin for a stain in a way that general protein or blood tests cannot.
Can Ehrlich's reagent be confused with the test of the same name used for indole alkaloids?+
Yes, the name is shared with the presumptive drug screen for LSD and related indoles, which uses the same core chromogen but is applied to a different sample type and target analyte, so case notes should specify which application was performed.
Related terms
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- Glycogen
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- Periodic Acid-Schiff (PAS) Reaction
- A histochemical staining method that oxidises polysaccharides (including glycogen) to produce aldehydes, which are then detected by Schiff reagent as a magenta...
- RSID-Vaginal Mucosa
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- Urobilinogen
- A colourless bile pigment metabolite produced by intestinal bacteria from bilirubin. It is excreted in faeces (as urobilin/stercobilin) and detected in forensic...