In the chemiluminescent reaction of Luminol in an aqueous solution, the luminol needs to react with molecular oxygen to produce a photon of blue light. In the technique, the hemoglobin of blood decomposes hydrogen peroxide to produce oxygen, which then react with the luminol. My issue is; wouldn't there already be oxygen present within the blood itself or from the environment that would react with the luminol itself? Am I missing something?
wouldn't there already be oxygen present within the blood itself or from the environment that would react with the luminol itself?
I'd say that's the exact reason why peroxide is added.
Without peroxide, the oxygen in blood stain may not contrast clearly enough with environmental oxygen, and you got uniform background (if detectable) luminescence everywhere.
With peroxide, the iron in blood stain suddenly produce huge extra amount of oxygen, and everywhere else the background is kept low, which gave away where the stains are.
That's if you are looking for the blood (with the help of oxygen). If you are looking for the oxygen itself, there should be other methods (electrochemical sensors, etc).