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A new solution 31 P NMR sample preparation scheme for marine sediments
Author(s) -
Defforey Delphine,
CadeMenun Barbara J.,
Paytan Adina
Publication year - 2017
Publication title -
limnology and oceanography: methods
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.898
H-Index - 72
ISSN - 1541-5856
DOI - 10.1002/lom3.10166
Subject(s) - authigenic , sediment , chemistry , pyrophosphate , nuclear magnetic resonance spectroscopy , extraction (chemistry) , apatite , carbonate , environmental chemistry , mineralogy , geology , chromatography , stereochemistry , organic chemistry , paleontology , enzyme
A new approach for the preparation of marine sediment samples for solution 31 P nuclear magnetic resonance spectroscopy ( 31 P NMR) has been developed and tested. This approach addresses important aspects associated with sample pretreatments for marine sediments, including the effects of sample pretreatment on sedimentary P composition. The method increases the signals of low abundance P species in 31 P NMR spectra by quantitatively and precisely removing up to 80% of inorganic P (orthophosphate) from sediment samples while causing minimal alteration of the chemical structure of organic P compounds. This method uses a reductive step to solubilize P bound to iron oxyhydroxides, followed by a low pH digestion to extract P from authigenic and biogenic apatite, as well as P bound to calcium carbonate. These P forms combined represent the most abundant inorganic P reservoir in marine sediments. The sample residue is then extracted in an alkaline solvent, 0.25 M NaOH with 0.05 M Na 2 EDTA, and processed for 31 P NMR spectroscopy. The method was tested on natural marine sediment samples from different localities with high inorganic P content (>85% molybdate reactive P), and allowed for the detection of orthophosphate monoesters and pyrophosphate in samples for which only an orthophosphate signal could be resolved with an NaOH‐EDTA extraction alone. This new approach will allow the use of 31 P NMR on samples for which low organic P concentrations previously hindered the use of this tool, and will help answer longstanding question regarding the fate of organic P in marine sediments.