2.5. Preparation of two-phase solvent system and sample solution
The selected solvent system, ethyl acetate–n-butyl alcohol–
water (1:4:5, v/v/v), was prepared by adding all the solvents to a
separation funnel according to the volume ratios and thoroughly
equilibrated by shaking separately. After thoroughly equilibrating,
the upper phase and lower phase were separated and degassed by
ultrasound for 30 min prior to use. The sample solution was prepared
by dissolving the crude sample in 5 ml upper phase of the
solvent system.