Forensic Analysis of Blood using Luminol

1. Forensic Analysis of Blood using Luminol

2. Luminol • Redox reaction with oxygen in the presence of catalyst produces a bright blue glow. • Used in forensic analysis for detection of blood • Iron in hemoglobin acts as catalyst • Other common catalysts • Biological: copper and cyanide • Laboratory: potassium ferricyanide Luminol 5-Amino-2,3-dihydro-1,4-phthalazinedione

3. Chemiluminescence • Chemical reaction produces an excited state compound • Excited state compound passes through intermediate • Decays to ground state • Emits a photon http://en.wikipedia.org/wiki/File:Luminol2006.jpg

4. Chemical Reactions • Luminol must be activated by hydroxide salt forming a dianion: • In the presence of iron (catalyst), hydrogen peroxide decomposes to form oxygen: 2H2O2 O2 + 2H2O -2 OH- 2 H20 + Luminol Dianion Dianion Fe

5. +O2 • The dianion reacts with oxygen producing the unstable organic peroxide intermediate: • This intermediate decomposes from higher energy states to the ground state, emitting a photon. Triplet Dianion(excited state) Dianion Intersystem Crossing hv Triplet Dianion (excited state) Singlet Dianion (excited state) Ground State *intersystem crossing is radiationless transition between different states of spin multiplicity

6. Chemiluminescence Triplet Dianion Singlet Dianion Energy Ground State Dianion As shown by the red dot, Luminol is excited into the triplet dianion state chemically. Through intersystem crossing, the molecule is able to transtion into the singlet dianion state of the same energy. Finally, the molecule fluoresces from the singlet dianion state to the ground state dianion emitting a photon of energy hv.

7. Advantages & Disadvantages • Advantages: • Fast • Easy • Disadvantages: • Fluoresces in the presence of other compounds, including bleach & horseradish • Can prevent other testing • Possible carcinogen

8. Application • Luminol can be used in a healthcare setting for contamination assessment