Presumptive test - Glossary - peptidetesting.cc

A presumptive test is a rapid screening method used as the initial step in a screen-then-confirm analytical workflow. It uses chemical or immunological signals to indicate the possible presence of a substance class. However, it does not confirm molecular identity, purity, or safety, signaling only that further confirmatory testing is required.

Main presumptive test formats and confirmatory methods

Color or 'spot' tests use reagents like Marquis or Mandelin to trigger visible reactions.
Immunoassays are common screening formats used in clinical and workplace drug testing.
Presumptive tests are sensitive but not specific, meaning unrelated chemicals can cause false positives.
A negative result does not definitively prove that a substance is absent from a sample.
Confirmatory methods such as GC-MS, LC-MS-MS, or LC-HRMS identify substances by reading their unique chemical signatures.

Screening results are not proof of identity without confirmation

A positive presumptive result from a color test or immunoassay is not proof of identity, purity, or safety. Without confirmatory mass spectrometry matched to a reference standard, the result remains a preliminary screen. This distinction is vital when reading a peptide lab report: a Certificate of Analysis (CoA) relying only on screening has not confirmed the actual substance.

A common misconception is that a positive color match equals confirmed identity or purity. It does not. These tests only signal the potential presence of a substance class and require professional confirmatory analysis to ensure the accuracy and safety of the research chemical.

Main presumptive test formats and confirmatory methods

Screening results are not proof of identity without confirmation

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