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How to Silanize Vials

In chemistry, samples are stored in vials to keep them from becoming contaminated and to prevent evaporation of volatile samples. Some samples contain compounds that interact with the surface of the glass walls of the vial. The interaction may allow the compounds to adhere or catalyze a reaction of the compound with the molecules at the surface of the glass. To prevent these problems, the process of silanizing or siliconizing the glass surface occurs.

The surface of the glass possesses silanol, or Si -- OH, groups, which are reactive with many classes of molecules. To eliminate the silanol sites, chlorosilanes are added by vapor deposition releasing a molecule of hydrochloric acid during the reaction. The hydrogen atom in the hydrochloric acid originated from the silanol group on the glass surface. The surface of the glass following the addition of chlorosilanes is composed of an unreactive Si -- O -- Si network. This network is much less likely to interact with sample compounds.

Things You'll Need

Fume hood
Vacuum dessicator
Vials
Small beaker of silanizing agent
Oven or autoclave

Instructions

- 1
  Place all items in the fume hood. Remove the lid of the dessicator and fill the dessicator with the vials and the beaker of silanizing agent. Replace the lid to limit the area of exposure to the vapors of the silanizing agent.
- 2
  Connect the dessicator to the vacuum line in the hood. Allow the pump to reduce the pressure inside the dessicator until the silanizing agent in the beaker begins to boil.
- 3
  Close the connection to the vacuum source once the silanizing agent begins to boil. The dessicator should remain at vacuum until the silanizing agent is gone. This process should require approximately 1 to 3 hours. During this time, the liquid silane evaporates and deposits on the surface of the vials. The silane molecules polymerize on the surface of the glass, sealing it from interaction with other compounds.
- 4
  Release the vacuum and open the dessicator once the liquid silane is gone and the waiting time has elapsed. Allow the dessicator to remain open to disperse any unreacted silane molecules.
- 5
  Place the vials into an oven or autoclave as a final step in sealing the reactive sites on the glass surface.

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