Proteomix® RP packings are porous polystyrene divinylbenzene (PS/DVB) polymer resins with narrow-dispersed particle size distribution. The base matrix of the resin is made of highly cross-linked PS/DVB which functions as reversed phase for chromatographic separation. The phase structure is phenyl and substituted phenyl functional groups that enable hydrophobic interaction. These highly rigid resins are provided with the particle size selection of 5, and 10 µm. In comparison to silica based reversed phase media, Proteomix® RP phases have advantages for biomolecule separations with wide pH range (1-14) and high thermal stability. At various column temperatures, the Proteomix® RP phases offer special selectivity, high resolution separation with online mass spec analysis capability for proteins such as mAb (monoclonal antibody), ADC (antibody drug conjugate) and related protein fragments.