Certified Sep-Pak Alumina A Vac cartridges contain a highly active grade of alumina with an acidic surface chemistry. The aluminum oxide surface provides an extremely polar surface for analyte retention and has properties of a Lewis acid. This normal phase sorbent is similar in use to silica; however, it is slightly more stable than unfunctionalized silica under high pH conditions. This acidic alumina is also low-capacity ion exchanger in aqueous media. Unlike polymer-based ion exhangers, this sorbent is unaffected by high-energy radioactivity and can be used for radioactive compound isolation. Certified Sep-Pak Alumina A cartridges are quality controlled to ensure reproducible separations. The cartridges provide superior performance for ultra-low level analyte detection by reducing the potential for background interferences found in many SPE devices. These syringe-barrel-type cartridges are designed for use with vacuum manifolds and automated SPE instruments.