Marquis reagent is used as a simple spot-test to presumptively identify alkaloids as well as other compounds. It is composed of a mixture of formaldehyde and concentrated sulfuric acid, which is dripped onto the substance being tested. The United States Department of Justice method for producing the reagent is the addition of 100 mL of concentrated (95–98%) sulfuric acid to 5 mL of 40% formaldehyde. Different compounds produce different color reactions. Methanol may be added to slow down the reaction process to allow better observation of the colour change.

History

Marquis reagent was first discovered and tested in 1896 by pharmacologist Eduard Marquis (1871–1944), then a student of Rudolf Kobert at the University of Dorpat (in Tartu, Estonia). The reagent was described by Marquis in his Master of Pharmacy dissertation in 1896 and subsequently named after him.

The reagent should be stored in the freezer for maximum shelf life.

thumb|The above photo shows the positive results of the number 2 Marquis reagent presumptive drug test when used with a sample of opium.

It is the primary presumptive test used in Ecstasy reagent testing kits. It can also be used to test for such substances as opiates (e.g. codeine, heroin), and phenethylamines (e.g. 2C-B, mescaline).

The test is performed by scraping off a small amount of the substance and adding a drop of the reagent (which is initially clear and colorless). The results are analyzed by viewing the color of the resulting mixture, and by the time taken for the change in color to become apparent.

Results

Reagent test results develop very quickly and due to reactions with moisture and oxygen in air, any changes after the first 60 seconds should be discarded.

|-

| DXM

| style="background-image: linear-gradient(to right, #aaaaaa, #000000); color:white" | gray to black

| 15–30 || Initially no change; takes much longer to reach black than MDMA

|}

{| class="wikitable sortable"

|+ Final colors produced by Marquis Reagent with various substances

|-

! Substance

! Color

|-

| βk-2C-B || Bright orange 30min

|-

| 2C-B || Green-yellow 30min

|-

| 2C-I || Green-yellow 30min

|-

| 2,5-Dimethoxy-4-bromoamphetamine (DOB) || Olive green – yellow

|-

| 2-FMA || Rapidly fizzes and dissolves. Colourless/light yellow

|-

| 25I-NBOMe || Orange

|-

| 25C-NBOMe || Clear, Transparent

|-

| 25B-NBOMe || Dark green

|-

| 4F-MPH || Transparent, no reaction

|-

| 5-EAPB || Purple to black

|-

| 5-MeO-MiPT || Clear/light brown

|-

| Aspirin || Pink > deep red

|-

| Adrafinil || Deep reddish orange – dark reddish brown

|-

| Benzphetamine || Deep reddish brown

|-

| Benzylpiperazine(BZP) || Clear (fizzes)

|-

| Buprenorphine || Pinkish violet

|-

| Butylone || style="background:#EDCF00; color:black" | Yellow

|-

| Dimethoxymethamphetamine HCL (DMMA) || Moderate olive

|-

| Doxepin || Blackish red

|-

| Dristan || Dark grayish red

|-

| Exedrine || Dark red

|-

| LSD || Clear (no reaction), charring of paper may occur

|-

| Methoxetamine || Slow pink

|-

| Morphine || Deep purplish red

|-

| Opium || Dark grayish reddish brown

|-

| Oxycodone || Pale violet

|-

| Propoxyphene || Blackish purple

|-

| Sugar || Dark brown

|}

Mechanism

The colour change from morphine is proposed to be a result of two molecules of morphine and two molecules of formaldehyde condensing to the dimeric product which is protonated to the oxocarbenium salt.

See also

  • Drug checking
  • Drug test
  • Dille–Koppanyi reagent
  • Folin's reagent
  • Froehde reagent
  • Liebermann reagent
  • Mandelin reagent
  • Mecke reagent
  • Simon's reagent
  • Zwikker reagent

References

  • Marquis reagent colors list, very comprehensive
  • DHPedia - Marquis reagent: A comprehensive list of colour reactions with photos. Archived from the original on November 12, 2020.