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EFFECTS OF HUMIC ACID PURIFICATION ON INTERACTION WITH HYDROPHOBIC ORGANIC MATTER: EVIDENCE FROM FLUORESCENCE BEHAVIOR. (R822832)
Citation:
Engebretson, R. R. AND W. A. von. EFFECTS OF HUMIC ACID PURIFICATION ON INTERACTION WITH HYDROPHOBIC ORGANIC MATTER: EVIDENCE FROM FLUORESCENCE BEHAVIOR. (R822832). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 33:4299-4303, (1999).
Description:
Conventional isolation of humic materials from natural
matrixes includes demineralization by treatment with HF/HCl. The possible effect of this on the structural integrity of
humic acid (HA) was investigated by comparing the
interactions of two aqueous HAs, one produced by the
conventional procedure (CHA) and the other by a gentler
resin method (RHA), with a hydrophobic probe (pyrene).
Although RHA had a substantially higher ash content, it was
found that this had relatively little effect on its interaction
with the probe molecule. In view of the micellar model
of dissolved HAs, however, it was noted that the HF-treated
HA had a greater apparent ability to sequester pyrene
and isolate it from the aqueous bulk. This was revealed
by the kinetics of probe fluorescence enhancement when
Mg2+ was added to a solution also containing HA and
by the anisotropy excitation spectra of the native humic
fluorophores. The effect was ascribed to a lesser degree
of conjugation in the HA demineralized with HF, producing
polymers of greater flexibility that formed micelle-like
structures more quickly and effectively.