Moye, Fabian; Bareth, Marlo; Koch, Boris P; Tebben, Jan; Harder, Tilmann: Dissolved organic matter molecular composition data of exemplary marine water masses resolved by online LC-MS [dataset bundled publication]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.974712 (dataset in review)

The unique chromatographic behaviour of DOM was investigated on three exemplary water samples representing coastal DOM, oceanic surface DOM and oceanic refractory DOM. Weddell Sea surface (30 m depth, oceanic surface DOM) and deep water (1356 m depth, refractory DOM) was sampled with a rosette sampler on RV Polarstern during ANT XXII/2 (station PS67/006-130, latitude -67.5633, longitude -55.3448) and are described elsewhere (El Naggar et al., 2007; Koch et al., 2008). 160 L sea water was filtered with 0.2 µm filter cartridges, acidified to pH 2 and pumped through 60 mL solid phase extraction cartridges (PPL, 5 g). DOM was eluted with 40 mL MeOH and stored at -18 °C. Coastal DOM is routinely extracted from southern North Sea (latitude 54.1447, longitude 7.8711) and used as an in-house laboratory standard. Sea water was filtered over 0.2 µm PTFE (Whatman), acidified to pH 2 and extracted with PPL cartridges. After elution with methanol, extracts are stored at -18 °C until measurement to minimize esterification (Flerus et al., 2011). The molecular composition was obtained by two mass spectrometric platforms with negative electrospray ionisation: 1) Fourier Transform Orbitrap mass spectrometer (FT-Orbitrap-MS; Q-Exactive Plus, Thermo Fisher Scientific, Bremen, Germany) coupled to ultra-high performance liquid chromatography (UPLC, Vanquish, Thermo Fisher Scientific, Bremen, Germany); 2) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS; 7 Tesla scimaX MRMS system, Bruker Daltonics GmbH & Co. KG, Bremen, Germany) coupled to UPLC (Elute LC, Bruker Daltonics GmbH & Co. KG, Bremen, Germany). Reversed phase chromatography was done with a C18 column (Waters AQUITY 2 x 100 mm, 1.7 µm) column at 0.3 mL min 1 and a linear gradient: A (ultrapure water, 4 mmol L 1 ammonium formate) 2 min: 99 %, 11 min: 0 %, 14.9 min: 99 %; B (MeOH, 4 mmol L 1 ammonium formate) 2 min: 1 %, 11 min: 100 %, 14.5 min 100 %, 14.9 min 1 %.