In general, all solid phase extraction (SPE) products are made of an empty cartridge, two frits (top frit and bottom frit), and sorbent media that is held between the frits as shown in the figure below. Materials for the cartridges are usually high-quality polypropylene, but some variations (e.g., glass) may be available. Frits are typically porous polyethylene, but in some SPE products PTFE or metal mesh may be used for specific applications. The sorbent media is where the separation of target compounds and interferences occurs through different modes of interaction between the sorbent media and your sample. The sorbent media is often called a “phase,”’ and it can be bonded or unbonded silica, polymeric materials, or various carbon materials.
