- P-ISSN 1225-0163
- E-ISSN 2288-8985
A humic acid(HA, Aldrich Co) sample was subjected to ultrafiltration for molecular size fractionation and three fractions of different nominal size(<TEX>$F_1$</TEX>: 1,000-10,000 daltons; <TEX>$F_2$</TEX>: 10,000-50,000 daltons; <TEX>$F_3$</TEX>: 100,000-300,000 daltons) were obtained. The structural characteristics of the size-fractionated HA were analyzed using their IR and solid state C-13 NMR spectral data, and the carboxylate group contents of the humic acids were determined using their pH titration data. The <TEX>$^7F_0-{^5}D_0$</TEX> excitation spectra of Eu(III) complexes of the size-fractionated mgHA in aqueous solution were acquired(<TEX>$[Eu(III)]