HPLC chromatograms showing pattern of separation in different trials (detection at 230 nm). (a) Final conditions chromatogram: pH 3.25 (phosphate buffer), Kromacil C18 column; (b) pH 2.8 (phosphate buffer), Kromacil column; (c) pH 4.0 (ammonium acetate buffer), Kromacil C18 column; (d) pH 3.25 (phosphate buffer), Grace Genesis Phenyl column; (e) pH 3.25 (phosphate buffer), Grace C18 Phenyl column.