The wavelengths of excitation/emission were 278/330 nm.
Sample was injected into a BEH Shield C18 (2.1 mm 50 mm; 1.7 lm)
with precolumn (Waters Corp., Milford, MA, USA) operated at
15 C, and the injection amount was 5 lL and flow rate was
0.5 ml/min. The elution solvents were 2.5% aqueous acetic acid
(A) and 100% acetonitrile (B).