The separation of vitamin C was carried out with
an ACE 5 C18 column (ACE, UK) (250 mm, 4.6 mm i.d., 5 lm)
thermostated at 25 C, using 5 mM KH2PO4 at pH 3.0 as the mobile
phase. Elution was done under isocratic conditions at a flow rate of
1 mL/min for 10 min. Injection volume was 20 lL and data acquisition
and processing were performed using the Agilent ChemStation
software (Agilent Technologies, Germany)