of the HS samples was performed using an FT MS spectrometer Bruker
Apex Ultra (Bruker Daltonics) equipped with a dynamically harmonized
cell, a 7 T superconducting magnet, and an electrospray ionization
(ESI) source. Each of the mass spectra were acquired in negative ionization
mode by direct infusion at a flow rate of 120 mL·h–1 by summarizing 400 scans. The internal calibration of the obtained
mass spectra was systematically conducted using the known peak series
of HS, reaching accuracy values of <0.5 ppm. Mass lists were created
using Data Analysis 3.4 software (Bruker Daltonics). Molecular assignments
were made using lab-made Transhumus software. Ion charge was directly
determined for abundant peaks using the m/z difference between 13C and 12C isotopologues,
and was extended for minor peaks using the total mass differences
algorithm.45 (link) Formulae were filtered using
the following typical atomic constraints: O/C ≤ 1, H/C ≤
2.2, C ≤ 120, H ≤ 200, 0 < O ≤ 60, and N ≤
2, S ≤ 1.