Spot Tests for Illegal Substances

Spot tests for Illegal substances

A number of various reagents can be prepared to quickly determine a class of drug compound.

Cocaine is known to react with Scott’s reagent (Cobalt thiocyanate)

In the presence of cobalt thiocyanate , cocaine will form a blue precipitate that will partition to the chloroform layer in an extraction.

To prepare cobalt thiocyanate one can add 6.8 grams of Cobalt Chloride and 4.3 grams ammonium thiocyanate to 100 mls water. Alternatively, one can add cobalt (II)sulfate to barium thiocyanate.

CoSO4(aq) + Ba(SCN)2(aq) → BaSO4(s) + Co(SCN)2(aq) The barium sulfate is insoluble and will precipitate out leaving the cobalt thiocyanate in solution.

To prepare a working stock of Scott’s reagent a few drops of glycerin is added to the cobalt thiocyanate solution.

Cocaine benzocaine diphenhydramine lidocaine

All of these will cross react to give a positive in the Scott’s test. Benzocaine is a popular local anaesthetic use to cut cocaine preparations.

Amphetaminesare known to react with Marquis reagent or Mandelin’s reagent.

In the Marquis reactions , an orange- red to brown color develops upon standing, and this product will fluoresce under long wave UV if a drop of water is added.

In the Mandelin’s reaction, a green to dark green color will form. This will turn a light red when heated.

To prepare the Marquis reagent: Add 10 drops of 40% formaldehyde to 10 mls of concentrated sulfuric acid.

To perform the test, add 1 drop to a pinch of sample.

To prepare the Mandelin’s reagent, dissolve 1 g of ammonium vanadate into 100 mls of concentrated sulfuric acid. To perform the test add 1 drop to a pinch of sample.

amphetamine ephedrine methamphetamine

All of the above will give a positive cross reaction in these assays.

Matrix of reactions for common assays and drugs.

Substance / Mandelin / Marquis / Mecke / Simon's / Robadope's
MDMA / dark purple / dark purple / dark purple / blue / no reaction
MDEA / dark purple / dark purple / dark purple / blue / no reaction
MDA / dark purple / dark purple / dark purple / no reaction / red
Methamphetamine / (dark) green / orange/brown / no reaction / blue / no reaction
Amphetamine / (dark) green / orange/brown / no reaction / no reaction / red
PMA / green to brown / no reaction / no reaction / no reaction / red
Ketamine / orange/brown / no reaction / no reaction / no reaction / no reaction
2C-B / no reaction / green / no reaction / no reaction / red
2C-I / no reaction / green / no reaction / no reaction / red
DXM / no reaction / grey with smoke / yellow / no reaction / no reaction
Opiates / no reaction / pink/red/purple / green / no reaction / no reaction
2C-T-xx / no reaction / no reaction / yellow to purple / no reaction / no reaction

In today’s lab, we will prepare these reagents and then test them against legally available forms known to cross react.

Samples: ephedra or pseudoephedrine tablets.

benzocaine lozenge

diphenhydramine (Benadryl) tablet.