Quantitative and qualitative comparison of marine dissolved organic nitrogen recovery using solid phase extraction

Carlos Miranda, Rene M. Boiteau, Amy M. McKenna, Angela N. Knapp

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Marine dissolved organic carbon and nitrogen (DOC and DON) are major global carbon and nutrient reservoirs, and their characterization relies on extraction methods for preconcentration and salt removal. Existing methods optimize for capturing and describing DOC. Here, we report an optimized analytical strategy to recover marine DON for subsequent molecular characterization. Retention efficiencies between 5% and 95% are reported for seven solid phase extraction (SPE) sorbents, with PPL recovering 23% of marine DON compared to 95% recovered with C18. Additional comparisons of the effect of varying sample volumes and elution speed, and the resulting molecular composition of DON extracts, were investigated using C18 and PPL sorbents. Sample volumes > 200 mL decreased DON retention efficiency independent of SPE sorbent, and gravity elution recovered 1.7- to 4.2-fold more DON compared to vacuum elution. Characterization of extracted DON by negative-ion electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) highlights compositional differences between DON species recovered by each method. DON isolated with optimized methods includes low molecular weight (< 600 Da) peptide-like compounds with low O:C ratios (0.2 to 0.5) that are not detected by other SPE sorbents (e.g., PPL). The majority of additional DON isolated with this approach was undetectable by direct infusion negative mode FT-ICR MS analysis.

Original languageEnglish (US)
Pages (from-to)467-477
Number of pages11
JournalLimnology and Oceanography: Methods
Volume21
Issue number8
DOIs
StatePublished - Aug 2023
Externally publishedYes

Bibliographical note

Funding Information:
A.N.K. gratefully acknowledges NSF-OCE 1537314 and NSF-OCE 2148989, which funded this work. We thank Taylor Broek for conversations. We also thank Markus Huettel for running extraction efficiency samples on his high temperature combustion machine for DON concentration analysis, and Huan Chen for assistance in data collection. A.M.M. was partially supported by the Gulf of Mexico Research Initiative, and funding for R.B. was from NSF-OCE 2149091. A portion of this work was performed at the Ion Cyclotron Resonance User Facility at the National High Magnetic Field Laboratory, which is funded by the National Science Foundation Division of Chemistry and Division of Materials of Research through NSF DMR 16-44779, and the State of Florida.

Funding Information:
A.N.K. gratefully acknowledges NSF‐OCE 1537314 and NSF‐OCE 2148989, which funded this work. We thank Taylor Broek for conversations. We also thank Markus Huettel for running extraction efficiency samples on his high temperature combustion machine for DON concentration analysis, and Huan Chen for assistance in data collection. A.M.M. was partially supported by the Gulf of Mexico Research Initiative, and funding for R.B. was from NSF‐OCE 2149091. A portion of this work was performed at the Ion Cyclotron Resonance User Facility at the National High Magnetic Field Laboratory, which is funded by the National Science Foundation Division of Chemistry and Division of Materials of Research through NSF DMR 16‐44779, and the State of Florida.

Publisher Copyright:
© 2023 Association for the Sciences of Limnology and Oceanography.

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