A method for a reversed phase chromatographic separation of active pharmaceutical ingredients (APIs) that are molecules with apolar and charged groups, preferably peptides, said method comprising evaluating the suitable reversed phase material, said material comprising surface modifying groups bound to a solid support that is silica gel, said surface modifying groups are not horizontally polymerized, said surface modifying groups comprising apolar uncharged groups and polar groups, wherein said polar groups being charged groups, said charged groups being either positively charged or negatively charged, and said charged groups being present in amounts of 0.25 to 22 % of the surface modifying groups, or in amounts of 0.01 μmol/m 2 to 0.8 μmol/m 2 referred to the surface of the solid support for a material with a total amount of surface modifying groups of 3.6 μmol/m 2, the surface modifying groups being bound to the surface via a reaction of monofunctional silanes, like monochlorosilanes, substituted with surface modifying groups or trimethoxysilanes substituted with surface modifying groups, the positively charged groups being -NR 3 + groups wherein R is selected from hydrogen or C1-C2 alkyl and the negatively charged groups being -SO 3 - groups, the charged groups are terminal substituents of aliphatic C1 to C18 groups, the apolar uncharged groups are linear C4 to C18 alkyl groups and the aliphatic groups of the charged groups are shorter by up to 6 CH 2 groups compared to the length of the apolar groups, and API purification conditions characterized by (a) determining the isoelectric point (pI) of the API of interest, (b) choosing a pH in a range between 3 and 9, (c) determining the difference pI-pH and (d) if the difference pI-pH is positive (pI > pH), choosing an anion exchange (AIEX) material, or if the difference pI - pH is negative (pI < pH), choosing an cation exchange (CIEX) material. evaluating the suitable reversed phase material, said material comprising surface modifying groups bound to a solid support that is silica gel, said surface modifying groups are not horizontally polymerized, said surface modifying groups comprising apolar uncharged groups and polar groups, wherein said polar groups being charged groups, said charged groups being either positively charged or negatively charged, and said charged groups being present in amounts of 0.25 to 22 % of the surface modifying groups, or in amounts of 0.01 μmol/m 2 to 0.8 μmol/m 2 referred to the surface of the solid support for a material with a total amount of surface modifying groups of 3.6 μmol/m 2, the surface modifying groups being bound to the surface via a reaction of monofunctional silanes, like monochlorosilanes, substituted with surface modifying groups or trimethoxysilanes substituted with surface modifying groups, the positively charged groups being -NR 3 + groups wherein R is selected from hydrogen or C1-C2 alkyl and the negatively charged groups being -SO 3 - groups, the charged groups are terminal substituents of aliphatic C1 to C18 groups, the apolar uncharged groups are linear C4 to C18 alkyl groups and the aliphatic groups of the charged groups are shorter by up to 6 CH 2 groups compared to the length of the apolar groups, and API purification conditions characterized by (a) determining the isoelectric point (pI) of the API of interest, (b) choosing a pH in a range between 3 and 9, (c) determining the difference pI-pH and (d) if the difference pI-pH is positive (pI > pH), choosing an anion exchange (AIEX) material, or if the difference pI - pH is negative (pI < pH), choosing an cation exchange (CIEX) material. (a) determining the isoelectric point (pI) of the API of interest, (b) choosing a pH in a range between 3 and 9, (c) determining the difference pI-pH and (d) if the difference pI-pH is positive (pI > pH), choosing an anion exchange (AIEX) material, or if the difference pI - pH is negative (pI < pH), choosing an cation exchange (CIEX) material.