Crocetin, a Water Soluble Carotenoid Monitor for Singlet Molecular Oxygen

The water soluble carotenoid crocetin has been studied as a singlet molecular oxygen monitor in D 2 O solution, pD 8.4. Crocetin reacts chemically with singlet molecular oxygen with a rate constant of 4 x 10 8 M ‐1 s ‐1 . The rate constant for total quenching, chemical and physical, is 2.5 x 10 9 M ‐1 s ‐1 . Crocetin shows evidence for a reversible reaction with singlet molecular oxygen, as demonstrated by a fairly rapid absorption recovery after bleaching.