minutes, and transferred to vial for injection. For this second method, seven preparations in matrix were used in the same way, each again spiked at ~500 ng L -1 of all analytes and also prepared in parallel with two sets of triplicates of unspiked samples which were later reconstituted after SPE either in injection solvent (for background subtraction) or with a ~50 ng L -1 solution of all analytes (as theoretical 100 % recovery), as above. The latter extracts were also used to evaluate matrix effect as above (see Table ). The same unspiked laboratory water sample prepared in triplicate with both methods was used for a comparison of the number of features generated pre-and post-reduction, as well as the number of substances detected. Suspect screening was separately performed for the features removed by the DOM filter, and library hits were manually reviewed to ensure no false negative results were generated by DOM features reduction (n=6).