Dataset: Sargassum photochem FTI-CR MS

For full details on irradiation experiments, please see Related Dataset page https://www.bco-dmo.org/dataset/938807.

The irradiation experiment described here was a separate experiment to couple with FT-ICR-MS analysis. Because a pH electrode was found to contaminate samples for mass spectrometry, no pH control was used in this experiment (sample pH ~ 4.5). Additionally, the sample volume was doubled compared to other experiments to minimize volume changes when subsampling. The absorbed photon dose was also decreased due to the larger volume, so that a 46 h time point was equivalent to ~20 h exposure in the previous irradiation experiments described in the Photodeg/pH dependence document mentioned above. At time points of 2, 4, 6, 22, and 46 h, 0.2 mL was sampled from the reactor and was added to 0.8 mL of methanol until analysis by ultrahigh resolution mass spectrometry (for full details please related FT-ICR-MS dataset https://www.bco-dmo.org/dataset/938847) using negative ion mode electrospray ionization (ESI). Only CHO formula assignments are described here because they were most abundant using negative ESI mode in the Sargassum SPE-DOM analyzed previously (Powers et al., 2019).