An Orbitrap Fusion MS
(Thermo Scientific,
USA) and a 9.4T Apex FT-ICR mass spectrometer (Bruker, Germany) were
used for the molecular composition analysis of DOM. Samples were infused
directly into the negative mode ESI sources at a speed of 180 μL/h.
The mass range for FT-ICR MS was m/z 200–800; detailed instrumental setting for FT-ICR MS is described
elsewhere.51 (link) For Orbitrap MS, the ranges
were m/z 150–800 for SRNOM
and 100–800 for SRFA. The instrument resolution mode was selected
as 500,000. The sampling duration was 2 min for each acquisition,
and the microscan was set at 3.37 (link),55 (link),58 (link) In the instrument parameter evaluation section, instrument parameters
such as ion spray voltage, sheath gas, aux gas, ion transfer tube
temperature, rf-lens, modified AGC target, and spectrums under different
parameters were acquired. Detailed instrument parameters are shown
in Table S1 (see theSupporting Information ).
(Thermo Scientific,
USA) and a 9.4T Apex FT-ICR mass spectrometer (Bruker, Germany) were
used for the molecular composition analysis of DOM. Samples were infused
directly into the negative mode ESI sources at a speed of 180 μL/h.
The mass range for FT-ICR MS was m/z 200–800; detailed instrumental setting for FT-ICR MS is described
elsewhere.51 (link) For Orbitrap MS, the ranges
were m/z 150–800 for SRNOM
and 100–800 for SRFA. The instrument resolution mode was selected
as 500,000. The sampling duration was 2 min for each acquisition,
and the microscan was set at 3.37 (link),55 (link),58 (link) In the instrument parameter evaluation section, instrument parameters
such as ion spray voltage, sheath gas, aux gas, ion transfer tube
temperature, rf-lens, modified AGC target, and spectrums under different
parameters were acquired. Detailed instrument parameters are shown
in Table S1 (see the
