Ehrlich's reagent or Ehrlich reagent is a reagent containing ''p''-dimethylaminobenzaldehyde (DMAB) and thus can act as an

indicator Indicator may refer to: Biology * Environmental indicator of environmental health (pressures, conditions and responses) * Ecological indicator of ecosystem health (ecological processes) * Health indicator, which is used to describe the health o ...

to presumptively identify

indole Indole is an aromatic heterocyclic organic compound with the formula C8 H7 N. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indole is widely distributed in the natural environme ...

s 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 A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, geneti ...

; some are

drug test A drug test is a technical analysis of a biological specimen, for example urine, hair, blood, breath, sweat, or oral fluid/saliva—to determine the presence or absence of specified parent drugs or their metabolites. Major applications of d ...

s and others contribute to

diagnosis Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engin ...

of various

disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

s or

adverse drug reaction An adverse drug reaction (ADR) is a harmful, unintended result caused by taking medication. ADRs may occur following a single dose or prolonged administration of a drug or result from the combination of two or more drugs. The meaning of this term ...

s. It is named after Nobel Prize winner

Paul Ehrlich Paul Ehrlich (; 14 March 1854 – 20 August 1915) was a Nobel Prize-winning German physician and scientist who worked in the fields of hematology, immunology, and antimicrobial chemotherapy. Among his foremost achievements were finding a cure ...

who used it to distinguish

typhoid Typhoid fever, also known as typhoid, is a disease caused by '' Salmonella'' serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several ...

from simple

diarrhoea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...

. 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 met ...

or other

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

-related issues. A very common Ehrlich test is a simple

spot test Spot analysis, spot test analysis, or spot test is a chemical test, a simple and efficient technique where analytic assays are executed in only one, or a few drops, of a chemical solution, preferably in a great piece of filter paper, without using ...

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

tryptamine Tryptamine is an indolamine metabolite of the essential amino acid, tryptophan. The chemical structure is defined by an indole ─ a fused benzene and pyrrole ring, and a 2-aminoethyl group at the second carbon (third aromatic atom, with the f ...

s (e.g. DMT) and ergoloids (e.g.

LSD Lysergic acid diethylamide (LSD), also known colloquially as acid, is a potent psychedelic drug. Effects typically include intensified thoughts, emotions, and sensory perception. At sufficiently high dosages LSD manifests primarily mental, vi ...

). 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 p ...

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 ...

, because of the presence of

tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromati ...

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 disor ...

, 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 Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a h ...

and 50 mL of concentrated

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dig ...

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 fer ...

, can also be used as well. The Ehrlich reagent is similar to a number of other indole tests: * The van Urk reagent, which uses 0.125 g of p-DMAB, 0.2 mL of

ferric chloride Iron(III) chloride is the inorganic compound with the formula . Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The colo ...

solution (25 g/mL) in 100 mL of 65% sulfuric acid. 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 Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solutio ...

(specific gravity 1.45) to methanol.

References

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

Medical testing

Preparation

See also

References