Diphenylamine (DPA) Test
Definition
A broad-spectrum presumptive colour test for nitrate and nitrite compounds, producing a blue-green coloration. Reactive with multiple oxidising agents, so environmental context is essential to interpreting a positive result.
- Detects
- Nitrate and nitrite compounds
- Positive result
- Blue-green coloration
- Result type
- Presumptive, not confirmatory
- Field
- Field explosives detection
Common questions
Why does the DPA test require environmental context to interpret?+
Many common oxidising agents besides explosive residues can trigger the colour change, so a positive result on soil, fertiliser residue, or vehicle exhaust particulate does not by itself confirm explosive material; the scene and item source have to be weighed alongside the chemistry.
What follow-up is needed after a positive DPA test?+
A confirmatory instrumental method, such as ion chromatography or mass spectrometry, is required before a nitrate or nitrite finding is reported as identified rather than merely presumptively indicated.
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