A solid–liquid extraction procedure followed by reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with a
photodiode array detector (DAD) for the determination of polyphenols in freeze-dried apple peel and pulp is reported. The extraction step
consists in sonicating 0.5 g of freeze-dried apple tissue with 30mL of methanol–water–acetic acid (30:69:1, v/v/v) containing 2 g of ascorbic
acid/L, for 10 min in an ultrasonic bath. The whole method was validated, concluding that it is a robust method that presents high extraction
efficiencies (peel: >91%, pulp: >95%) and appropriate precisions (within day: R.S.D. (n = 5)