Refining 31P nuclear magnetic resonance spectroscopy for marine particulate samples: Storage conditions and extraction recovery
✍ Scribed by Barbara J. Cade-Menun; Claudia R. Benitez-Nelson; Perry Pellechia; Adina Paytan
- Book ID
- 104041255
- Publisher
- Elsevier Science
- Year
- 2005
- Tongue
- English
- Weight
- 518 KB
- Volume
- 97
- Category
- Article
- ISSN
- 0304-4203
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✦ Synopsis
Solution 31 P nuclear magnetic resonance (NMR) spectroscopy has recently been used to characterize phosphorus species within marine particles. However, the effects of sample collection, storage and preparation have not been thoroughly examined. In this study, samples of settling particulates collected from a 1200-m sediment trap located in Monterey Bay, California, were subjected to various storage options (i.e., no storage, refrigeration, freezing, and oven-drying and grinding) prior to extraction for solution 31 P-NMR spectroscopy. Freezing, refrigerating and drying samples for periods of up to 6 months prior to extraction with 0.25 M NaOH+ 0.05 M Na 2 EDTA increased the concentration of extracted P by an average of 16% relative to samples extracted without storage. Pre-extraction storage also introduced some minor changes in P speciation, by increasing the percentage of orthophosphate by up to 15% and decreasing the percentage of pyrophosphate by up to 5%, relative to the abundances of these P species in samples extracted without storage. Drying caused the biggest changes in speciation, specifically decreasing more extensively the relative percentage of pyrophosphate compared to other treatments. Nevertheless, observed changes in speciation due to sample storage within a specific sample were small relative to differences observed among samples collected sequentially in the same area, or reported differences among samples collected at different locations. Samples were also analyzed by solid-state 31 P-NMR spectroscopy before and after extraction, to examine extraction-related changes in P speciation. Comparison of solution with solid-state 31 P NMR indicates that extraction with NaOH-EDTA removes the majority of organic esters, but only a variable portion of phosphonates (39-67%). In addition, there was preferential extraction of Ca-associated phosphate over Mg-, Fe-and Al-associated phosphate. Solution 31 P NMR enables much higher resolution of P species within samples, particularly when it is important to speciate orthophosphate monoesters and diesters, or if polyphosphates are present. However, combining solid-state 31 P NMR with