The present invention relates to a method of purifying peptides and/or polypeptides, said method comprising or consisting of: (a) loading a sample comprising peptides and/or polypeptides under acidic or neutral aqueous conditions on mixed-phase solid phase extraction (SPE) material, wherein said material consists of or comprises reversed phase/ion exchange material; (b) washing said mixed-phase SPE material with (ba) an acidic or neutral composition comprising at least 50% (v/v) organic solvent; and/or (bb) an acidic or neutral aqueous solution; and (c) eluting said peptides and/or polypeptides from said mixed-phase SPE material with an alkaline composition comprising at least 50% (v/v) organic solvent.