2.6. HPLC–ESI-MSn conditions
HPLC–ESI-MSn analyses were carried out on an Agilent Tech-
nologies modular 1200 system, equipped with a vacuum degasser,
a binary pump, a thermostated autosampler, a thermostated col-
umn compartment and a 6310A ion trap mass analyzer with an
ESI ion source. The HPLC column and the applied chromatographic
conditions were the same as reportedfor theHPLC-UV/DAD system.
The flow-rate was split 3:1 before the ESI source.
The experimental parameters were set as follows: the capillary
voltage was 3.5 kVfor the positive ion mode and 4.0 kVfor the nega-
tive ion mode, respectively; the nebulizer (N2) pressure was 35 psi,
the drying gas (N2)temperature was 350 ◦C,the drying gas flow was
11 L/min and the skimmer voltage was 40V. Data were acquired by
Agilent 6300 Series Ion Trap LC/MS system software (version 6.2).
The mass spectrometer was operated in the full-scan positive and
negative ion mode in the m/z range 100–1000. MS2 and MS3 spec-
tra were automatically performed with helium as the collision gas
in the m/z range 50–1000 with the SmartFrag function.