Marquis Reagent: The Complete Guide to the Most Important Drug Checking Tool
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Top Picks at a Glance
| Award | Product | Price | |
|---|---|---|---|
| Essential Reagent | Marquis Reagent Test Kit — Detects MDMA, Meth, Speed & Opiates | $25.00 | Check Price |
| Best Starter Bundle | Essential Drug Test Kit (3-in-1) | $60.00 | Check Price |
| Full Lab | Elite Drug Test Kit (10-in-1) | $150.00 | Check Price |
What Is Marquis Reagent?
Marquis reagent is a chemical testing solution that produces specific color reactions with various psychoactive substances. First discovered and tested in 1896 by the pharmacologist Eduard Marquis (1871-1944) for forensic toxicology, it remains the most widely used drug checking reagent in the world.
Chemical composition: Formaldehyde (CH₂O) in concentrated sulfuric acid (H₂SO₄)
What Marquis Detects
Marquis is a general-purpose screening reagent that reacts with a wide range of substances. Key reactions: MDMA/MDA (purple → black, instant), amphetamine (orange → brown), methamphetamine (orange → red-brown), heroin (purple → dark purple), and 2C-B (yellow → green).
Critical safety signal: Marquis produces NO reaction with PMA/PMMA. If a sample sold as MDMA does not turn purple with Marquis, you may have PMA, which has caused numerous fatalities.
How to Use
Place a match-head-sized sample on a clean white ceramic plate. Add 1-2 drops of Marquis. Observe color within 30 seconds. Note both the initial color and any changes over 2-3 minutes.
Shelf Life
Unopened and refrigerated: 12-18 months. Opened and refrigerated: 6-12 months. Opened at room temperature: 3-6 months. Signs of degradation: brown or pink discoloration means replace immediately.
Frequently Asked Questions
Does Marquis detect fentanyl?
No. Marquis does not detect fentanyl. Use fentanyl test strips for fentanyl detection. Marquis can confirm whether a white powder is an opioid versus another class of drug.
Can Marquis distinguish MDMA from MDA?
No. Both produce a similar purple → black reaction with Marquis. Use Simon's reagent to distinguish MDMA (secondary amine, turns blue) from MDA (primary amine, no reaction).
What does it mean if Marquis does not react?
It could mean the substance is cocaine, ketamine, LSD, caffeine, MSM, or PMA/PMMA (major red flag if sold as MDMA). Use additional reagents based on what you expect the substance to be.
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Last updated 2026-07-25. Prices verified against TestKitPlus at time of update and may change. Testing reduces risk — it never eliminates it.