The present invention is, inter alia, peptides, in particular cyclic or non-cyclic peptides their analogs, or relates to the field of purification of the derivative. More particularly, the present invention is simplification of the cyclic peptide, and, a optimized purification steps, higher desired final product yield, by chromatographic methods which allow selectivity, and the purity, the above peptide with respect to purification process from a composition comprising at least one related impurity. Its improved process, eptifibatide, exenatide, atosiban, nesiritide, are particularly useful in the preparation of their respective derivatives and analogs. The polypeptide, at least about 96%, and preferably are prepared in at least about 99% of high purity.