The Oasis MCX on-line column is designed for rugged, reproducible, and ultra-fast on-line SPE. The column contains the Oasis MCX sorbent, which is a novel, mixed-mode polymeric sorbent that has been optimized to achieve higher selectivity and sensitivity for extracting basic compounds with cation-exchange groups. The Oasis MCX on-line column is designed for use with the appropriate Waters narrow-bore analytical column, such as XSelect, XBridge, SunFire, Atlantis, XTerra, or Symmetry column. The column features traditional HPLC column fittings and hardware.