Optimization of ESI-MS/MS Conditions. To achieve
optimum conditions to identify as many PMFs in the peels of
STJ as possible, all factors related to MS performance including
ionization mode, nebulizer gas pressure, electrospray voltage of
the ion source, and collision energy have been evaluated. The
results showed that ESI in positive ion mode was more sensitive
to PMFs than ESI in negative ion mode. The major
constituents were well detected (shown in Figure 2), and
most of the investigated compounds exhibited quasi-molecular