Peat humic acid was fractionated by tangential ultrafiltration intosixnominalmolecularweight(NMW)fractions,HA5-10,HA10-20, HA20-50, HA50-100, HA100-300 and HA>300, which were purified by dialysis usinga0.5kDamembrane.Theabsorbingandemission properties of the separated fractions were compared and their ability to generate singlet oxygen under light excitation was evaluated, using furfuryl alcohol (FFA) as a singlet oxygen scavenger. The absorbance, the emission intensity, and the apparent first order rate constants of FFA loss were normalized per mole of organic carbon (a*, IF*, and k*, respectively). The fraction absorbance decreased with NMW, except for HA>300 which was less absorbing than HA100-300. The low NMW fractions and the HA>300 fraction generally showed lower k* and IF* values compared to the HA50-100 and HA100-300 fractions. A plot of k* versus IF* indicates that the first order rate constant of FFA photo-oxygenation increased with the intensity of fluorescence at 380, 430, and 500 nm (R2 ) 0.77-0.84). This shows that the distribution of fluorescent centers among fractions paralleled that of photosensitizing centers. Plotting k* or IF* versus a* at 365nmreveals the apparent relativequantum efficiency of the different fractions. Higher values for low NMW fractions and HA50-100 are either due higher percentages of absorbing centers able to produce singlet oxygen or exhibit fluorescence or to lower quenching processes.
Relationship between Photosensitizing and Emission Properties of Peat Humic Acid Fractions Obtained by Tangential Ultrafiltration / Cavani L.; Halladja S.; Ter Halle A.; Guyot G.; Corrado G.; Ciavatta C.; Boulkamh A.; Richard C.. - In: ENVIRONMENTAL SCIENCE & TECHNOLOGY. - ISSN 0013-936X. - ELETTRONICO. - 43:(2009), pp. 4348-4354. [10.1021/es802964m]
Relationship between Photosensitizing and Emission Properties of Peat Humic Acid Fractions Obtained by Tangential Ultrafiltration
CAVANI, LUCIANO;CIAVATTA, CLAUDIO;
2009
Abstract
Peat humic acid was fractionated by tangential ultrafiltration intosixnominalmolecularweight(NMW)fractions,HA5-10,HA10-20, HA20-50, HA50-100, HA100-300 and HA>300, which were purified by dialysis usinga0.5kDamembrane.Theabsorbingandemission properties of the separated fractions were compared and their ability to generate singlet oxygen under light excitation was evaluated, using furfuryl alcohol (FFA) as a singlet oxygen scavenger. The absorbance, the emission intensity, and the apparent first order rate constants of FFA loss were normalized per mole of organic carbon (a*, IF*, and k*, respectively). The fraction absorbance decreased with NMW, except for HA>300 which was less absorbing than HA100-300. The low NMW fractions and the HA>300 fraction generally showed lower k* and IF* values compared to the HA50-100 and HA100-300 fractions. A plot of k* versus IF* indicates that the first order rate constant of FFA photo-oxygenation increased with the intensity of fluorescence at 380, 430, and 500 nm (R2 ) 0.77-0.84). This shows that the distribution of fluorescent centers among fractions paralleled that of photosensitizing centers. Plotting k* or IF* versus a* at 365nmreveals the apparent relativequantum efficiency of the different fractions. Higher values for low NMW fractions and HA50-100 are either due higher percentages of absorbing centers able to produce singlet oxygen or exhibit fluorescence or to lower quenching processes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
