ABA was eluted with 1.5 ml of 80% methanol and vacuumed to dryness again,redissolved in 40l of 20% acetonitrile and injected 5l into a
Waters Acquity SQD UPLC-MS system (Waters, Milford, USA),
a BEHC18 (100mm×2.1mm, 1.7m) column was used in
the UPLC,the mobile phase was 20% acetonitrile. Flow rate
was 0.25ml/min and the column temperature was 30 ◦C.