Mecke Reagent
Definition
Selenious acid (H2SeO3) dissolved in concentrated sulphuric acid. More selective than Marquis for the opioid alkaloid skeleton; morphine and heroin give a blue-green to blue colour, while simple amphetamines give little or no colour.
- Composition
- Selenious acid in concentrated sulphuric acid
- Positive for opioids
- Blue-green to blue with morphine, heroin
- Response to amphetamines
- Little or no colour
- Test type
- Presumptive colour test
Common questions
Why is Mecke reagent used alongside Marquis rather than instead of it?+
Marquis reacts broadly across many drug classes and can give similar colours for different substances, so analysts run Mecke in parallel because its selectivity for the opioid skeleton helps narrow down which class of drug is present before confirmatory instrumental analysis.
Does a positive Mecke result confirm the presence of heroin?+
No, a colour test is presumptive only. A blue-green to blue reaction indicates an opioid alkaloid is likely present, but confirmation for evidentiary purposes requires an instrumental method such as GC-MS.
Related terms
- 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...
- 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...
- 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...
- Marquis Reagent
- A presumptive drug test reagent consisting of formaldehyde in concentrated sulphuric acid, first described by Edmund Marquis in 1896. It produces characteristic...
- NIK Polytesting
- A field drug testing approach using the NIK Public Safety sealed ampoule system, where multiple colour tests are run sequentially on the...
- Scott Test
- A three-step cobalt thiocyanate presumptive test for cocaine and its salts. Step 1: cobalt thiocyanate reagent (blue in aqueous phase). Step 2:...
- Simon's Test
- A presumptive test that uses sodium nitroprusside and sodium carbonate to detect secondary amines (N-methyl group). Methamphetamine and MDMA (secondary amines) give...
- SWGDRUG Category C
- The lowest tier in the Scientific Working Group for the Analysis of Seized Drugs classification. Category C methods (including colour tests, microcrystal...