The column was washed for impurities successively with 3 mL
loading solvent and then 2 mL washing solvent. After the washing
solvent had flowed through the top filter, the column was eluted
with eluting solvent. The outflow solution from the column did not
contain ABA and was discarded during the column was applied the
loading and washing solvents and the first 1.0 mL after changed to
eluting solvent. Then, 2 mL eluent was collected as purified ABA
solution for HPLC analysis.