Determination of picomolar dissolved free amino acids along a South Atlantic transect using reversed-phase high-performance liquid chromatography

Sabadel, AJM; Browning, TJ; Kruimer, D; Airs, RL; Woodward, EMS; Van Hale, R; Frew, RD. 2017 Determination of picomolar dissolved free amino acids along a South Atlantic transect using reversed-phase high-performance liquid chromatography. Marine Chemistry, 196. 173-180. https://doi.org/10.1016/j.marchem.2017.09.008

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Abstract/Summary

Dissolved free amino acids (DFAA) in seawater are a form of nitrogen (N) available for marine microbes. In oligotrophic environments where N-containing nutrients are the limiting factor for microbial growth, N nutrition from DFAA could be crucial, but as yet it is poorly resolved. Measurements of individual DFAA are challenging as concentrations are typically in the low nmol L− 1 range. Here we report modifications to methodology using o-phthaldialdehyde (OPA) derivatization and reversed phase high performance liquid chromatography (HPLC) that provide a 30-fold improvement in sensitivity enabling the detection of 15 amino acids in seawater with a limit of detection as low as 10 pmol L− 1 with accuracy and precision of better than 10%. This analytical methodology is now suitable for the challenging quantitation of DFAA in oligotrophic seawaters. The method was successfully applied to a suite of seawater samples collected on a cruise crossing the South Atlantic Ocean, where concentrations of DFAAs were generally low (sub nmol L− 1), revealing basin-scale features in the oceanographic distributions of DFAA. This unique dataset implies that DFAAs are an important component of the N cycle in both near-coastal and open oceans. Further calculations suggest that the proportions of organic N originating from DFAA sources were significant, contributing between 0.2 and 200% that of NH4+ and up to 77% that of total inorganic nitrogen in the upper 400 m in some regions of the transect.

Item Type: Publication - Article
Subjects: Chemistry
Marine Sciences
Oceanography
Divisions: Plymouth Marine Laboratory > Science Areas > Marine Biochemistry and Observations
Depositing User: Ruth Airs
Date made live: 03 Jul 2018 12:02
Last Modified: 20 May 2019 01:58
URI: http://plymsea.ac.uk/id/eprint/7812

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