We are presenting a biochemistry laboratory exercise that demonstrates free radical reactions and quenching with the anti-oxidant ascorbic acid. Using a luminometer to measure photons to developing this technique, we noted the lack of free radical generation with the addition of ascorbic acid (AA) in the presence of a variety of buffers. It was eventually determined that the AA dropped the pH sufficiently to inhibit the potassium ferrocyanide/hydrogen peroxide initiation of luminol-generated free radicals. After trying several buffer to hold the pH above 10.5. A sodium bicarbonate buffer was shown to be optimal for this procedure, so as to avoid the student falsely belieiving that the AA was quenching the free radical reaction due to its antioxidant properties and not due to a drop in pH.

pH effects upon luminol reactions quenched by ascorbic acid

243rd National Meeting (2012)

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