Monday, June 18, 2007 - 8:35 AM
Snake River (Boise Centre on the Grove)

31P Chemical shift anisotropy in humate-phosphate complexes

Jeremy Riggle and Ray Von Wandruszka. University of Idaho, Moscow, ID

The mobility of inorganic phosphate (P) attached to solid humic acid (HA) and fulvic acid via a metal "anchor" was investigated by 31P-NMR spectroscopy. The peak width of the 31P resonance was monitored as an indicator of its chemical shift anisotropy, which reveals its mobility in the humic matrix. The concept was demonstrated by contrasting peak widths of thoroughly dry HA-M-P complexes with those that had been allowed to absorb different amounts of moisture. It was shown that the presence of moisture, which enhances the mobility of P, results in a significant reduction of chemical shift anisotropy. The work was extended to comparisons between dry systems with and without metal anchors; systems with anchors consisting of different metals; systems comprising different humates and fulvates; and systems different size fractions of a humate. It was shown that both the type of humate/fulvate, and the metal anchor used lead to different degrees of mobility within the humic matrix. It was also found that the effect of metal addition on 31P peak width is greater with fulvates and smaller HA fractions than with the larger HA components.