Special mixed layer of silica and a strongly acidic cation exchanger coated to polyester plates. The coating thickness is 200um and dimensions are 20x20cm. There are 25 plates per pack. Applications include: Amino acids, e.g., in protein and peptide hydrolysates, in seeds and fodder, in biological fluids; for racemate separation in peptide syntheses, for the separation of nucleic acid hydrolyzates, amino sugars, amino acids, antibiotics, inorganic phosphates, cations and other compounds with ionic groups.