Marquis Reagent
Definition
A presumptive drug test reagent consisting of formaldehyde in concentrated sulphuric acid, first described by Edmund Marquis in 1896. It produces characteristic colours with aromatic amines and opioid alkaloids through electrophilic aromatic substitution and oxidative cyclisation reactions.
- Composition
- Formaldehyde plus concentrated sulfuric acid
- First described
- 1896 by Edmund Marquis
- Test type
- Presumptive color-based screening (Category C, requires confirmation)
Common questions
What is Marquis reagent made of?+
Marquis reagent is formaldehyde mixed with concentrated sulfuric acid. It was first described by Edmund Marquis in 1896. The reaction works through electrophilic aromatic substitution and oxidative cyclisation.
What color does Marquis reagent turn with different drugs?+
The reagent produces different colors depending on the substance. Heroin and morphine turn it purple-black. Amphetamine and MDMA turn it purple to violet, while amphetamines alone produce an orange-brown color. Aspirin turns it yellow-orange, and cocaine shows no color change.
Why is Marquis reagent called a presumptive test?+
Marquis reagent is presumptive because the color change suggests the presence of a drug but does not definitively identify it. It is a Category C technique under SWGDRUG standards, so a positive result always requires confirmatory testing with more specific methods before drawing conclusions.
Related terms
- 6-Monoacetylmorphine (6-MAM)
- A transient diagnostic metabolite of heroin (diacetylmorphine) formed by the rapid hydrolysis of one acetyl group. Half-life is 6 to 25 minutes...
- Duquenois-Levine Test
- A three-reagent presumptive test for cannabinoids: vanillin + acetaldehyde in ethanol (Reagent 1), concentrated hydrochloric acid (Reagent 2), and chloroform partition (Reagent...
- 4-Anilinopiperidine Scaffold
- The structural core conserved across fentanyl and its analogues: a piperidine ring bearing an anilide group at the 4-position. Clandestine variation at...
- Alkaloid Ratio Profiling
- A source-attribution technique using the morphine:codeine:papaverine:noscapine ratio in heroin seizures to infer the geographic origin of the opium feedstock, reflecting the chemotype...
- Benzoylecgonine
- Major urinary metabolite of cocaine. Detected by immunoassay screen and LC-MS-MS confirmation; window of detection 2 to 4 days for occasional use.
- Carfentanil
- A fentanyl analogue with a 4-carbomethoxy substituent on the piperidine ring; approximately 10,000 times the analgesic potency of morphine. Implicated in the...
- Cobalt Thiocyanate
- Co(SCN)2 in aqueous solution; the active reagent in the Scott test for cocaine. Cocaine forms a lipophilic blue complex with cobalt thiocyanate...
- Diacetylmorphine
- The IUPAC name for heroin; the 3,6-diacetyl ester of morphine, produced by acetylation with acetic anhydride. More lipophilic than morphine, crosses the...
- Dose Heterogeneity
- The variation in active ingredient content between nominally identical tablets in a counterfeit or clandestinely pressed batch. High dose heterogeneity in illicit...
- False Positive (Presumptive Test)
- A positive colour response from a compound that is not the targeted controlled substance. Common sources include diphenhydramine (Marquis orange, Scott blue),...
- Mandelin Reagent
- Ammonium metavanadate (NH4VO3) in concentrated sulphuric acid. Useful for amphetamines (orange-red), MDMA (dark blue-black) and cocaine (yellow-orange). The Mandelin-Marquis panel is recommended...
- Mecke Reagent
- Selenious acid (H2SeO3) dissolved in concentrated sulphuric acid. More selective than Marquis for the opioid alkaloid skeleton; morphine and heroin give a...
Explained in these topics
- Opioids: Heroin, Fentanyl Analogues and Prescription DiversionsA colour-based presumptive test: concentrated H2SO4 with formaldehyde. Purple-black with heroin and morphine; orange-brown with amphetamines; no response with...
- Presumptive Colour Tests: Marquis, Mecke, Duquenois-Levine, Cobalt Thiocyanate and ScottA presumptive drug test reagent consisting of formaldehyde in concentrated sulphuric acid, first described by Edmund Marquis in 1896. It produces characteristi...
- Stimulants, Narcotics and Opiates: Forensic ToxicologyFormaldehyde plus concentrated sulfuric acid. Orange-brown to purple-black with opiates, purple to violet with amphetamine / MDMA, yellow-orange with aspirin.