Ehrlich's reagent or Ehrlich reagent is a

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

containing ''p''-dimethylaminobenzaldehyde (DMAB) and thus can act as an indicator to presumptively identify indoles and

urobilinogen Urobilinogen is a colorless by-product of bilirubin reduction. It is formed in the intestines by bacterial action on bilirubin. About half of the urobilinogen formed is reabsorbed and taken up via the portal vein to the liver, enters circulation an ...

. 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. It is named after Nobel Prize winner Paul Ehrlich who used it to distinguish typhoid from simple diarrhoea. The Ehrlich reagent works by binding to the C2 position of two indole moieties to form a resonance stabilised carbenium ion compound.

Medical testing

Ehrlich reagent can be used to detect

, which can indicate

jaundice Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme meta ...

or other liver-related issues. A very common Ehrlich test is a simple spot test to identify possible

psychoactive A psychoactive drug, psychopharmaceutical, psychoactive agent or psychotropic drug is a chemical substance, that changes functions of the nervous system, and results in alterations in perception, mood, consciousness, cognition or behavior. Th ...

compounds such as tryptamines (e.g.

DMT ''N'',''N''-Dimethyltryptamine (DMT or ''N'',''N''-DMT, SPL026) is a substituted tryptamine that occurs in many plants and animals, including human beings, and which is both a derivative and a structural analog of tryptamine. It is used as a ...

) and

ergoloid Ergoloid mesylates (USAN), co-dergocrine mesilate ( BAN) or dihydroergotoxine mesylate, trade name Hydergine, is a mixture of the methanesulfonate salts of three dihydrogenated ergot alkaloids ( dihydroergocristine, dihydroergocornine, and a ...

s (e.g. LSD). It gives a negative test-result for

25I-NBOMe 25I-NBOMe (2C-I-NBOMe, Cimbi-5, Smiles and also shortened to "25I") is a synthetic hallucinogen that is used in biochemistry research for mapping the brain's usage of the type 2A serotonin receptor; it is also sometimes used for recreational pu ...

and many other non-indole-related psychoactives. The reagent will also give a positive result for

opium Opium (or poppy tears, scientific name: ''Lachryma papaveris'') is dried latex obtained from the seed capsules of the opium poppy ''Papaver somniferum''. Approximately 12 percent of opium is made up of the analgesic alkaloid morphine, which i ...

, because of the presence of tryptophan in natural opium.

Pyridoxine Pyridoxine, is a form of vitamin B6 found commonly in food and used as a dietary supplement. As a supplement it is used to treat and prevent pyridoxine deficiency, sideroblastic anaemia, pyridoxine-dependent epilepsy, certain metabolic disorde ...

, present in

vitamin supplements A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrien ...

, can give positive results to the Ehrlich test, showing a pink colour change.

Preparation

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 Propan-1-ol (also propanol, n-propyl alcohol) is a primary alcohol with the formula and sometimes represented as PrOH or ''n''-PrOH. It is a colorless liquid and an isomer of 2-propanol. It is formed naturally in small amounts during many ferme ...

, can also be used as well. The Ehrlich reagent is similar to a number of other indole tests: * The

van Urk reagent A van is a type of road vehicle used for transporting goods or people. Depending on the type of van, it can be bigger or smaller than a pickup truck and SUV, and bigger than a common car. There is some varying in the scope of the word across ...

, which uses 0.125 g of p-DMAB, 0.2 mL of ferric chloride solution (25 g/mL) in 100 mL of 65%

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

. This is sometimes referred to as the Hofmann reagent or p-DMAB-TS (Test Solution) and gives slightly different colours with different indoles. * 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 1.45) to

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

References

Chemical tests Analytical reagents Drug testing reagents Paul Ehrlich {{chem-stub

Medical testing

Preparation

See also

References