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Soil and Litter Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy

Extractants, Metals, and Phosphorus Relaxation Times

^a Dep. of Environmental Sciences, Policy and Management, Univ. of California at Berkeley
^b College of Chemistry, Univ. of California at Berkeley
^c Stanford Magnetic Resonance Lab., Stanford Univ., Stanford, CA 94305-2115

View larger version (20K): [in a new window]   Fig. 1. Spectra for soil (a) and litter (b) extracted with 0.25 M NaOH, 0.25 M NaOH plus 6:1 Chelex to soil or litter (wt. basis), or 1:1 0.5 M NaOH plus 0.1 M EDTA. Spectra are the 3.2 s recovery delay time data for each respective interleaved series of saturation-recovery experiments.

View larger version (20K): [in a new window]   Fig. 2. The T1 relaxation spectra for litter extracted with NaOH-EDTA in a 1:1 mix. All spectra are plotted at the same scale illustrating the effect of increasing recovery delays times on signal intensities. Spectra were acquired as an interleaved series of saturation–recovery experiments. For this series, six T1 recovery delay times were used (0.1, 0.2, 0.4, 0.8, 1.6, and 3.2 s) and data was acquired through eight cycles of the delay list at 232 scans per delay per cycle resulting in a total of 1856 scans per delay time.

View larger version (31K): [in a new window]   Fig. 3. Spectra are shown for two identically prepared samples before and after (a) T1 data acquisition in the NMR magnet (14 h at 32°C) and (b) incubation in an oven (17 h at 30°C). The difference spectra are the result of subtracting the respective before and after spectra from each other. Significant changes in the phosphonate region can be clearly seen (dotted lines). Apparent differences in the orthophosphate monoester region (*) are likely due to subtraction artifacts. Both samples are litter extracted with NaOH-EDTA.