*Rubber septum consists of a disk of rubber or similar material used to seal a vial or other device. It is installed along the inside of a cap, which is typically made of metal or plastic. A syringe needle pierces the rubber septum for the purpose of injection and, on withdrawal, the elasticity of the septum ensures that the hole reseals.
*Rubber septa are most commonly used to seal medicinal vials containing either a liquid or freeze-dried solid (which is then liquefied in water or other substance). The medicine is drawn from the vial using a needle, then injected. Septa may also be used when a substance either needs to be injected into or pulled from a vial (or other device) then re-sealed.
- Rubber septa to seal vials used to store samples in a lab. These vials are typically used in conjunction with either a gas or liquid chromatograph.
- Sealing the injection port on top of a gas chromatograph. These injection port septa are meant to seal the entire chromatographic column.
- Sealing test ports on chemical or pharmaceutical processing equipment. When samples need to be taken in a closed system, use of an injection port septum may be a good way to insert a needle to take a sample without having to shut the entire system down.
*Rubber septum design varies widely depending on the application. Medicinal vial septa are typically compression molded out of Silicone or Butyl rubber in multi-cavity molds within a high controlled manufacturing environment. Other septum types may include a chemical barrier layer, most commonly PTFE, or in extreme case, two barrier layers. These designs are most often punched from a sheet of rubber.
*The quality of the barrier film and rubber are extremely important for many reasons. A poor quality septum may lead to improper re-sealing, skewed test results, or poor quality product. To minimize this, manufacturing inputs must be strictly controlled.