2.8. Profiling of antioxidants by post-column derivatization
The chromatographic profiles of antioxidants in plant juices
studied were obtained by post-column online derivatization with
ABTS reagent injected to HPLC eluate using Pinnacle PCX Derivatization
Instrument (Pickering Laboratories, Inc., USA) according
to Kusznierewicz et al. (2011). The ABTS derivatization reagent
was prepared by dissolving ABTS in aqueous sodium persulphate
(2.45 mmol/L) to obtain concentration of 7 mmol/L and diluting it
with methanol after 12 h to the stock concentration of 2 mmol/L.
The flow rate of the derivatization reagentwas set at 0.2 mL/min. In
all experiments, the 0.5 mL coil (PTFE, 0.25 mm,10 m)was used and
derivatization reaction was carried out at 130 C. The profiles
showing bleaching of ABTS following reaction with antioxidant
compounds present in the eluate from HPLC column were monitored
at 734 nm using a multiple wavelength detector (Agilent
1200 Series MWD, USA).