A mixture of 40 % of solution A(met

A mixture of 40 % of solution A
(methanol:acetic acid:water were 10:0.3:89.7 v/v/v) and 60 %
of solution B (methanol:acetic acid:water were 90:0.3:9.7 v/v/
v) was used as the mobile phase with a flow rate of
0.5 ml minÀ1, as described by Kim et al. (2006), except that isocratic elution was used instead of gradient elution. Authentic
IAA (Sigma, USA) was used as a standard.