Colorimetric tests for the detection of drugs in beverages: limitations and precautions

This article aims to inform about colorimetric tests in general and their scientific limits. It does not concern any brand or product in particular and is part of an awareness-raising approach on prevention against chemical submission.

Colorimetric tests for detecting drugs in beverages are often presented as tools to protect against chemical submission. Some claim to be able to identify several hundred substances, giving the impression of reliable protection against drugs commonly used in this type of aggression.

But these promises can sometimes be misleading. Colorimetric tests have significant limitations that can create a false sense of security. This article examines the strengths and weaknesses of this technology and suggests complementary solutions for optimal protection.

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1. An ambitious promise: “hundreds of substances detected”

❌ A statement to be qualified

The lack of publicly available independent scientific validation makes it difficult to verify claims that these tests detect a very wide range of substances. Colorimetric tests work on the basis of precise chemical reactions that target certain families of molecules. They cannot cover all known drugs.

✅ Scientific reality

These tests are often designed to detect substances such as GHB and ketamine, which have chemical properties that allow for a colorimetric reaction. However, the detection of other substances such as amphetamines, cocaine or benzodiazepines relies on different methods, which can limit their effectiveness.

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2. Colorimetric tests: how do they work?

❌ Limited coverage

A colorimetric test relies on a chemical reaction between the substance being tested and a reagent. However, each test only reacts to certain chemical structures, which means that a single test cannot cover a complete spectrum of substances.

Additionally, several factors can influence the results:

• The acidity and composition of the drink can interact with the test.
• The color of the liquid may mask colorimetric reactions.
• The concentration of the substance being tested may be too low to be detected.

✅ Why these tests remain useful

Despite their limitations, these tests can be used as an additional precautionary tool, particularly for GHB and ketamine. However, it is crucial not to rely on them exclusively.

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3. False positives and false negatives: an underestimated danger

❌ Sometimes misleading results

Some liquids, such as red wine or dark sodas, may react with the test and cause false positives. Conversely, a drug present at too low a concentration may not be detected, causing a false negative.

✅ Best practices

A reliable test must have validated detection thresholds to ensure usable results. It is recommended to cross-reference colorimetric tests with other prevention methods.

📌 The importance of detection thresholds Each colorimetric test has a specific detection threshold that determines the minimum concentration of a substance needed to cause a visible reaction. These thresholds vary depending on the manufacturer and the targeted substance. It is therefore essential to consult the test data sheets in order to understand at what concentration these devices react . A test with a threshold that is too high may not detect a drug that is present in small quantities in a drink. Conversely, a threshold that is too low could generate an excessive number of false positives.

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4. Comparison with other detection methods

Criteria	Colorimetric Test	Saliva Test	Urine Test	Laboratory Analysis
Substances detected	GHB, ketamine mainly	Recent drugs (THC, cocaine, MDMA, etc.)	Prolonged drug use	Broad spectrum of substances
Method	Chemical reaction	Immunochromatography	Immunochromatography	Chromatography / mass spectrometry
Reliability	Risks of false positives/negatives	Very reliable for recent consumption	High precision	Extreme precision
Detection of other drugs	Limited	Yes (cocaine, amphetamines, THC, etc.)	Yes (all drugs according to test)	Yes (drugs and metabolites)
Immediate use	Yes	Yes	Yes	No (lab required)

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5. Prevention: what alternatives?

✅ Additional recommended measures

• Never leave your drink unattended.
• Favor scientifically validated tests.
• Use physical devices (glass hoods, safety caps).
• Be vigilant in party areas.

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