SWGDRUG Category C
Definition
The lowest tier in the Scientific Working Group for the Analysis of Seized Drugs classification. Category C methods (including colour tests, microcrystal tests, and fluorescence microscopy) have the lowest analytical discriminating power and cannot be used alone for drug identification. At least one Category A method is required for a confirmatory identification.
- Working group
- SWGDRUG
- Tier
- Lowest of the category system
- Example methods
- Colour tests, microcrystal tests, fluorescence microscopy
- Limitation
- Cannot confirm identification alone
- Requirement
- At least one Category A method needed for confirmation
Common questions
Why can't a Category C method confirm a drug's identity on its own?+
Category C tests such as colour or microcrystal tests respond to a class of compounds rather than a single specific substance, so a positive result narrows the possibilities without uniquely identifying the drug. A structurally specific Category A technique, such as mass spectrometry, is needed to rule out other compounds giving the same presumptive reaction.
What role do Category C tests still play if they can't confirm identity?+
They are used as rapid, low-cost screening tools at the scene or early in the lab workflow to triage samples and decide priorities, before the sample goes on to a confirmatory Category A method for the final reportable identification.
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...
- Mecke Reagent
- Selenious acid (H2SeO3) dissolved in concentrated sulphuric acid. More selective than Marquis for the opioid alkaloid skeleton; morphine and heroin give a...
- 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...