Diphenylamine Test
Definition
Color test for nitrates and nitro groups. Diphenylamine in conc. H2SO4 turns deep blue with oxidising NO3-/NO2-. Also a primer-residue test, which is why it overlaps with the GSR bullet.
- Reagent
- Diphenylamine in concentrated sulfuric acid
- Positive result
- Deep blue coloration
- Detects
- Nitrate and nitro-group oxidisers
- Secondary use
- Primer gunshot-residue screening
Common questions
Why does the diphenylamine test overlap between explosives and GSR casework?+
Both propellant and many explosive formulations contain nitrate or nitro-group oxidisers, so the same colour reaction can flag either type of residue; the analyst has to use the item's context and follow-up instrumental analysis to tell them apart.
Is the deep blue colour specific to a particular explosive?+
No, it is a class test for oxidising nitrate and nitro compounds generally, not a specific identification, so a positive result only justifies further confirmatory testing rather than naming a compound.
Related terms
- GC-TEA
- Gas chromatography with a Thermal Energy Analyser. Pyrolytic cleavage of the nitro group to NO followed by chemiluminescent reaction with ozone. Nitro-specific,...
- IMS
- Ion Mobility Spectrometry. Drift-tube separation of gas-phase ions at ambient pressure. Smiths IONSCAN 500DT and Sabre 5000 give 5-second field screening on...
- Ion Chromatography (IC)
- An analytical technique that separates and quantifies anions and cations in solution. In post-blast residue analysis, IC detects nitrate, nitrite, ammonium, and...
- Janowski Test
- Color test for nitroaromatics. Sample plus DMSO plus alcoholic KOH gives a violet Meisenheimer complex. Positive for TNT, picric acid, tetryl and...
- Modified Griess Test
- A contact-transfer colour chemistry test for nitrite-containing propellant combustion residue. Sulphanilic acid undergoes diazotisation with nitrous acid (from NO2 on the target...
- Post-Blast Residue (PBR)
- Unconsumed explosive plus reaction by-products left at the seat of an explosion, on debris, on fragments and on the hands or clothing...
- VBIED
- Vehicle-Borne Improvised Explosive Device. Pulwama 2019 is the recent Indian reference case (RDX plus ammonium nitrate).