Luminol is a chemical that produces beautiful blue fluorescence upon oxidation by hydrogen peroxide. In addition to one of the best known examples of chemiluminescence, it is also a valuable tool for investigating crime scenes whose blue glow reveals the presence of blood.
For teachers, demonstrating the luminol response can contribute to discussions about oxidation reduction reactions, energy savings and electron energy levels. The following demonstration is ideal for high and high school students.
Materials
1 g of Luminol
20 ml sodium hydroxide solution (1 M)
10 ml hydrogen peroxide (3%)
0.2 g of potassium ferricyanide
piece of rubber hose
Funnel
Ring stand
Tripod
Clamps
Preparation
You need a separate cup for each of the 2 stock solutions you are going to prepare. Prepare the solutions immediately before use. Put on a lab coat or apron, glasses and gloves before preparing solutions. Note: hydrogen peroxide is a strong oxidizer. Avoid skin contact. Sodium hydroxide and its solutions are corrosive and may irritate the skin. Avoid skin contact.
To prepare stock solution A, fill a beaker with 100 ml of water. Add 0.18 g of luminol and 3.0 ml of sodium hydroxide solution (1 M).
To prepare stock solution B, fill another beaker with 100 ml of water. Add 1 ml of hydrogen peroxide (3%) and 0.03 g of potassium ferricyanide.
Experiment
DIM the lights.
At the same time, pour an equal amount of solution A and solution B into the funnel.
While the 2 solutions are mixing, a blue light is emitted that is relatively bright and should last several minutes. hellionchem
Technical information
Fluorescence indicator, peroxidase reagent
3-Aminophthalic hydrazide, 5-Amino-2,3-dihydro-phthalazine-1,4-dione
Empirical formula C8H7N3O2
Molar mass (M) 177.16 g / mol
Melting point (mp) approx. 320 ° C
WGK 1
CAS No. [521-31-3]
EC no. 208-309-4
Luminol (C8H7N3O2) is a chemical that exhibits chemiluminescence, with a blue glow, when mixed with an appropriate oxidizing agent. Luminol is a white-to-pale-yellow crystalline solid that is soluble in most polar organic solvents, but insoluble in water.
Forensic investigators use luminol to detect trace amounts of blood at crime scenes, as it reacts with the iron in hemoglobin. Biologists use it in cellular assays to detect copper, iron, cyanides, as well as specific proteins via western blotting.
When luminol is sprayed evenly across an area, trace amounts of an activating oxidant make the luminol emit a blue glow that can be seen in a darkened room. The glow only lasts about 30 seconds, but investigators can document the effect with a long-exposure photograph. Crime scene investigators must apply it evenly to avoid misleading results, as blood traces appear more concentrated in areas that receive more spray. The intensity of the glow does not indicate the amount of blood or other activator present, but only shows the distribution of trace amounts in the area. hellionchem.com
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