Methods of improving recombinant protein titer and cell titer in cell culture using cell culture media having reduced impurities are provided, and well as cell culture media having reduced impurities that can used for the production of a recombinant protein and cells with improved titer. The cell culture media having reduced impurities comprises a HEPES buffer, and the reduced impurities are HEPES related impurities. In certain aspects, methods and media improve protein titer, cell growth, and/or viable cell density.