Luminol
Definition
A chemiluminescent reagent (5-amino-2,3-dihydro-1,4-phthalazinedione) that produces blue-white light on contact with haemoglobin-derived iron. Detects blood diluted to 1:10,000,000 or more. Used as a presumptive test for bloodstains, especially after attempted cleaning.
- Test type
- Chemiluminescent presumptive test
- Detection mechanism
- Reacts with hemoglobin iron in blood to produce blue light
- Sensitivity
- Detects blood at dilutions of 1:1,000,000
- Key limitation
- Presumptive only; can partially degrade surface DNA
Common questions
How sensitive is luminol for detecting blood?+
Luminol can detect blood at extremely high dilutions, around 1 in 1,000,000. This makes it one of the most sensitive tests for finding blood stains, even when someone has tried to clean them up.
What happens when luminol reacts with blood?+
Luminol is oxidized in an alkaline hydrogen peroxide solution. When it contacts the iron in hemoglobin from blood, it undergoes a chemiluminescent reaction that produces a distinctive blue glow visible in the dark.
Can luminol confirm that a stain is blood?+
No. Luminol is a presumptive test, not a confirmatory one. It will react with blood but can give false positives with other substances. A positive result must be followed by confirmatory tests before concluding the stain is blood.
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Explained in these topics
- Biological Sample Screening and Presumptive TestsA chemiluminescent reagent (5-amino-2,3-dihydro-1,4-phthalazinedione) that produces blue-white light on contact with haemoglobin-derived iron. Detects blood di...
- Body-Fluid Identification: Presumptive and Confirmatory TestsChemiluminescent blood presumptive test detecting haem iron at dilutions exceeding 1:1,000,000. Used for large-area scene searches; not confirmatory; partially...
- Detection and Identification of Blood Stains in Forensic ScienceChemiluminescent presumptive test. Luminol oxidised in alkaline hydrogen peroxide in the presence of haem iron emits blue light visible in darkness. Sensitivit...