Plexa PCX is a new polymer-based cation exchange SPE medium that combines the excellent performance of Bond Elut Plexa (such as higher flow characteristics and better analytical performance) with the functionality of strong cation exchange. This new mixed SPE adsorbent removes neutral and acidic interferences from the matrix and concentrates basic analytes, thus improving the sensitivity in the determination of basic compounds. Plexa PCX is ideal for applications in pharmacokinetics and pharmacodynamics, forensic and toxicology, food and environmental analysis.