Marquis reaction
The Marquis reaction is a wet chemical detection of "activated aromatics ", which is carried out using the Marquis reagent .
Marquis reagent
The reagent for the substance sample consists of concentrated sulfuric acid and formaldehyde solution . A mixing ratio of
- 1 part formaldehyde solution (40%)
to
- 20 parts of concentrated sulfuric acid (approx. 95-98%).
application
The Marquis reaction is a classic detection of alkaloids , especially for morphine - derivatives (eg. Codeine , apomorphine ), the red under these conditions resulting deep violet color.
Since this evidence is sensitive and, due to the appearance of different colors , enables different substances to be distinguished, it is part of the standard repertoire of various pharmacopoeias and textbooks in forensic chemistry.
Overall, however, the reaction is not very specific. With the Marquis reagent, for example, morphine turns purple and turns purple. The reaction can also be used to detect other drugs such as B. papaverine and tolazoline (AB-DDR) are suitable.
In addition, the reagent for detection of MDMA , amphetamine , rare 2C-B and opiates in the drug scene a certain notoriety within the Pill testing obtained (commercially in this context EZ-Test called). In fact, this test can only be used to conclude that the substance in question is definitely not contained in the event of a negative result . A positive reaction, on the other hand, does not guarantee that it does not contain other ingredients. The concentration of the respective active ingredient, for example MDMA in an “Ecstasy” pill, cannot be determined with this test.
Reaction sequence
The exact reaction mechanism of the Marquis reaction is not known for all substances that give a positive detection (i.e. a colored product). In general, the Marquis reaction seems to be formally an addition of formaldehyde to an activated aromatic and subsequent oxidative dimerization , similar to the chromotropic acid reaction . The formaldehyde protonated at the oxygen atom by the added acid attacks in the sense of an electrophilic aromatic substitution , and after the bond formation the proton is released again. This first step is followed by an oxidation step and the addition of a further aromatic molecule. The intermediate product splits off a hydroxyl group under the influence of sulfuric acid , which leads to the formation of a mesomerism-stabilized , colored cation (" halochromy "). The product for morphine derivatives has been relatively well researched. If these are detected , two molecules of the respective alkaloid react with two molecules of formaldehyde.
Individual evidence
- ↑ S. Ebel and HJ Roth (editors): Lexikon der Pharmazie , Georg Thieme Verlag, 1987, p. 412, ISBN 3-13-672201-9 .
- ↑ Color Test Reagents / Kits for Preliminary Identification of Drugs Of Abuse, National Institute of Justice Standard - 0604.01
- ↑ H. Auterhoff , D. Braun Arch. Pharm. 306 , 866 (1973).