Characterization of a Newly Available Coastal Marine Dissolved Organic Matter Reference Material (TRM-0522)

Abstract

Recent methodological advances have greatly increased our ability to characterize aquatic dissolved organic matter (DOM) using high-resolution instrumentation, including nuclear magnetic resonance (NMR) and mass spectrometry (HRMS). Reliable DOM reference materials are required for further method development and data set alignment but do not currently exist for the marine environment. This presents a major limitation for marine biogeochemistry and related fields, including natural product discovery. To fill this resource gap, we have prepared a coastal marine DOM reference material (TRM-0522) from 45 m deep seawater obtained ∼1 km offshore of Sweden’s west coast. Over 3000 molecular formulas were assigned by direct infusion HRMS, confirming sample diversity, and the distribution of formulas in van Krevelen space was typical for a marine sample, with the majority of formulas in the region H/C 1–1.5 and O/C 0.3–0.7. The extracted DOM pool was more nitrogen (N)- and sulfur (S)-rich than a typical terrestrial reference material (SRFA). MZmine3 processing of ultrahigh-performance liquid chromatography (UPLC)-HRMS/MS data revealed 494 resolvable features (233 in negative mode; 261 in positive mode) over a wide range of retention times and masses. NMR data indicated low contributions from aromatic protons and, generally speaking, low lignin, humic, and fulvic substances associated with terrestrial samples. Instead, carboxylic-rich aliphatic molecules were the most abundant components, followed by carbohydrates and aliphatic functionalities. This is consistent with a very low specific UV absorbance SUVA254 value of 1.52 L mg C–1 m–1. When combined with comparisons with existing terrestrial reference materials (Suwannee River fulvic acid and Pony Lake fulvic acid), these results suggest that TRM-0522 is a useful and otherwise unavailable reference material for use in marine DOM biogeochemistry.

Direct Analysis of Marine Dissolved Organic Matter Using LC-FT-ICR MS

“…Our LC-FT-ICR MS method allowed the direct injection of 100 μL of filtered seawater resulting in more than 200 single DOM mass spectra at a mass resolving power of ∼500,000 at m / z 400. The marine DOM eluted from the column in a broad, unstructured peak between 13 and 25 min (Figure ), as observed previously for aquatic DOM extracts. ,,− Owing to the very low amount of injected DOM and long accumulation times (here: 1.6 s), the total ion chromatogram (TIC) showed a less pronounced DOM peak as compared to previous studies using concentrated DOM extracts. , However, DOM sample TICs were clearly distinguishable from blank injections (Figure SI 4), and the total assigned ion chromatograms (TAC) clearly showed the DOM elution profile (Figure ). Compared to a peak width of individual model compounds of less than 0.5 min (full-width half-maximum (FWHM), cf.…”

“… 23 , 28 , 33 − 35 Owing to the very low amount of injected DOM and long accumulation times (here: 1.6 s), the total ion chromatogram (TIC) showed a less pronounced DOM peak as compared to previous studies using concentrated DOM extracts. 23 , 36 However, DOM sample TICs were clearly distinguishable from blank injections ( Figure SI 4 ), and the total assigned ion chromatograms (TAC) clearly showed the DOM elution profile ( Figure 1 ). Compared to a peak width of individual model compounds of less than 0.5 min (full-width half-maximum (FWHM), cf.…”

Preparation of Simple Bicyclic Carboxylate-Rich Alicyclic Molecules for the Investigation of Dissolved Organic Matter

“…■ METHODS Reference Materials. The reference standard TRM-0522 30 was used as received and dissolved in 5% acetonitrile to a concentration of 2 mg/mL for injection by LCMS. TRM-0522 was isolated from a coastal setting at 45 m depth on the west coast of Sweden using an aqueous-compatible C 18 sorbent.…”

“…TRM-0522 was isolated from a coastal setting at 45 m depth on the west coast of Sweden using an aqueous-compatible C 18 sorbent. It is a well-defined reference mixture 30 containing thousands of molecular formulas, the majority of which are defined as "CRAM" according to the definitions in Hertkorn et al's work. 19 Liquid Chromatography.…”

“…Finally, we propose that the development of methods for the preparation of accurate RDOM standards will lead to improvements for the quantification of DOM globally. As a proof of concept, a series of four CRAM molecules (Figure , 9 – 12 ) and their partially oxidized counterparts were prepared (Figure , 13 – 16 ), and their NMR, MS, MS2, and HPLC spectra were directly compared with representative data sets from the marine DOM standard TRM-0522 . TRM-0522 was chosen for comparison, as it is low in aromatic content and is the only standard mixture available from a marine source containing DOM that is recalcitrant in this environment.…”