High-resolution mass spectrometry (HRMS) has become a vital tool for dissolved organic matter (DOM) characterization in aquatic systems. The upward trend in HRMS analysis of DOM presents challenges in data comparison and interpretation among laboratories operating instruments with differing performance and user operating conditions. It is therefore essential that the community establishes metric ranges and compositional trends for data comparison with reference samples so that data can be robustly compared among research groups. At the ASLO conference in Victoria, 2018, a small group of aquatic scientists working with mass spectrometry decided to address this need by initiating an international ring trial, in which the same four samples from the International Humic Substances Society would be analysed by as many laboratories as possible, in order to determine instrument variability, publish benchmark metric values for ongoing use, and reduce scientific and communication barriers. The laboratory comparison was a great success – 16 laboratories with 17 commercially purchased instruments participated, and analysed the samples in positive and negative electrospray ionization modes. Instrument variability was rather high in terms of the mass window (the range of masses) that they were tuned to, but largely garnered the same information from the four samples, because DOM has so many repeating patterns over the whole mass range. About 1000 common ions were found in each mode for each sample, and the detection of these can be used for establishing and testing new methods. The metrics produced for weighted averages of O/C, H/C, m/z and aromaticity can be used for putting all new results into international context in future studies that use one of the four standard mixtures.

Primary Presenter: Juliana D'Andrilli, Louisiana Universities Marine Consortium (jdandrilli@lumcon.edu)

Authors:

Jeffrey Hawkes, Uppsala University  (jeffrey.hawkes@kemi.uu.se)

David Podgorski, University of New Orleans  (dcpodgor@uno.edu)