Clean Screen®. Clean Screen phases are true co-polymeric sorbents that contain hydrophobic and ion exchange functional groups uniquely polymerized to a silica substrate. The design and quality of Clean Screen provides more efficient, robust and clean extraction of drugs from biological matrices. CLEAN SCREEN® phases are true co-polymeric sorbents that contain hydrophobic and ion exchange functional groups uniquely polymerized to a silica substrate. Mixed-mode separations allow maximum selectivity for extraction of acidic, neutral and basic compounds. This selectivity makes Clean Screen ideal for both screening and confirmation analysis for virtually all drug categories. The Clean Screen® product line (adsorbents and columns) provides superior sample clean up, recovery and reproducibility.