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Phosphorus‐31 Nuclear Magnetic Resonance Spectral Assignments of Phosphorus Compounds in Soil NaOH–EDTA Extracts
Author(s) -
Turner Benjamin L.,
Mahieu Nathalie,
Condron Leo M.
Publication year - 2003
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2003.4970
Subject(s) - chemistry , phosphorus , phosphate , nucleic acid , phosphorus 31 nmr spectroscopy , nuclear magnetic resonance spectroscopy , extraction (chemistry) , polyphosphate , sugar phosphates , nuclear chemistry , organic chemistry , biochemistry
Soil P composition can be conveniently determined in alkaline extracts using solution 31 P nuclear magnetic resonance (NMR) spectroscopy, but spectral assignments are based on fragmentary literature reports of model compounds in various extraction matrices. We report solution 31 P NMR chemical shifts of model P compounds, including inorganic phosphates, orthophosphate monoesters and diesters, phosphonates, and organic polyphosphates, determined in a standardized soil P extractant (0.25 M NaOH and 0.05 M EDTA). Signals from nucleic acids (DNA −0.37 ppm, RNA 0.54 ppm) and phospholipids (phosphatidyl choline 0.78 ppm, phosphatidyl serine 1.57 ppm, phosphatidyl ethanolamine 1.75 ppm) could be differentiated in the orthophosphate diester region, and were identified in a sample of cultured soil bacteria. Inorganic and organic polyphosphates could be differentiated by the presence of a signal at −9 ppm from the α phosphate of organic polyphosphates. Some orthophosphate diesters, notably RNA and phosphatidyl choline, degraded rapidly to orthophosphate monoesters in NaOH–EDTA although DNA, other phospholipids, and orthophosphate monoesters were more stable. Changes in probe temperature had a marked influence on signal intensities and the relative magnitude of signals from orthophosphate monoesters and inorganic orthophosphate, and we suggest that solution 31 P NMR spectroscopy of soil extracts be performed at 20°C.