Figure 2.

Schematic of the untargeted metabolomics approach established and applied in the present study for the analysis of LMW DOM from Arctic soil water extracts. After the filtration step, triplicate extracts for each section of the core (n = 9) were split and handled separately. The resulting concentrated aliquots (18 samples) were run on two LC phases and in two MS polarities, resulting in four analytical conditions per sample. RT: retention time. ESI (+/−): electrospray ionization positive or negative mode. DDA: data-dependent acquisition (unbiased precursor selection for MS² fragmentation).