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Solid-state and multidimensional solution-state NMR of solid phase extracted and ultrafiltered riverine dissolved
Edith Kaiser1, Andre J Simpson, Karl J Dria
1Swiss Federal Institute of Environmental Science and Technology (EAWAG), Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland. edith.kaiser@eawag.ch
Environmental Science & Technology
|July 24, 2003
Summary
This study compared two methods for isolating dissolved organic matter (DOM) from river water. Nuclear Magnetic Resonance (NMR) spectroscopy revealed that each technique selected different compound types, impacting the characterization of aquatic organic matter.
Area of Science:
- Environmental Chemistry
- Organic Geochemistry
- Analytical Chemistry
Background:
- Dissolved organic matter (DOM) is crucial in aquatic ecosystems.
- Understanding DOM composition is key to biogeochemical processes.
- Isolation techniques can influence the characterization of DOM.
Purpose of the Study:
- To compare the chemical composition of DOM isolated by solid-phase extraction (SPE) and ultrafiltration (UF).
- To elucidate differences in DOM isolates from an oligotrophic river using multidimensional NMR.
- To assess the impact of isolation methods on DOM characterization.
Main Methods:
- Solid-phase extraction (SPE) and ultrafiltration (UF) for DOM isolation.
- Multidimensional solution-state Nuclear Magnetic Resonance (NMR) spectroscopy (1D, 2D TOCSY, HMQC).
- 1D solid-state 13C NMR spectroscopy for bulk characterization.
Main Results:
- Both SPE and UF recovered up to 42% of total DOM.
- Solid-state 13C NMR showed minor spatial-temporal changes in bulk DOM composition.
- 2D NMR revealed SPE-isolated DOM was rich in aliphatic esters, ethers, and hydroxyls.
- UF-isolated DOM contained peptides/proteins and some aliphatic/fatty acids.
- Sugars were detected in both DOM fractions.
Conclusions:
- SPE and UF isolate distinct chemical constituents from the bulk DOM pool.
- The choice of isolation technique significantly affects the perceived chemical composition of DOM.
- NMR spectroscopy is effective in differentiating DOM fractions based on isolation method.