Sterilization of Glass Containers and Vials

While most types of glass can be sterilized by steam or dry heat, specific sterilization methods are recommended for certain types of glass. Most USP Type I borosilicate glass is suitable for sterilization and depyrogenation when proper procedures are followed. Repeated steam sterilization is not recommended for Type III glass, although it may be suitable for single use. The recommended autoclave cycle conditions are: 121°C, 15 psi, for 20 minutes. Container lids should be kept loose. Extreme caution must be exercised during venting, otherwise, the containers may be damaged.

Dry heat sterilization can be performed at 160°C for 2 to 3 hours, but glass containers can withstand sterilization temperatures up to 500°C without significant glass damage. Repeated dry heat sterilization of containers containing significant amounts of moisture may lead to glass spalling. Inverting the containers and ensuring good ventilation can prevent this. Before each use, inspect glass containers for chips, cracks, and scratches; damaged containers should be discarded, as they may break during sterilization if used again.
 

Glass containers can also be sterilized using gases or chemicals. Suitable for heat-sensitive areas or rapid turnaround: Vaporized hydrogen peroxide (vH₂O₂): Used for surface sterilization of vials in isolators, at room temperature, with no residue, but requires a dedicated chamber and validation. Peracetic acid/hydrogen peroxide rinse: Kills spores after 10–30 minutes of contact, suitable for bottle caps, stoppers, or colored glass bottles, but requires thorough rinsing and residue validation.

When material limitations prevent the use of heating and pressurization methods, ethylene oxide (EtO), formaldehyde, or peroxide gases are commonly used. Common chemical disinfectants include quaternary ammonium compounds, iodophors, formalin, benzalkonium chloride, and ethanol.

Glass containers can also be sterilized using irradiation; however, this process changes the color of the glass, which may be unacceptable for most applications. Some glass tubing is available that does not discolor after irradiation. This type of glass tubing is only available to customers requiring large volume orders of glass tubing. Sterilization of Glass Containers and Vials: Other Auxiliary/In-line Technologies: UV-C Tunnel: Surface sterilization only, often used as a "bioburden reduction" step before filling, and cannot replace final sterilization. Ozone or Electron Beam: Can be used in continuous production lines, but requires high equipment investment and confirmation of glass and closure material compatibility.

General Operating Points for Sterilization of Glass Containers and Vials:
1. Cleaning: New bottles should be rinsed with detergent and tap water, then soaked in nitric acid (1+1) or chromic acid cleaning solution, and finally rinsed with purified water; bottles that have contained highly hazardous components are recommended to be discarded.
Loading: Leave gaps between bottles to avoid contact with the walls; for large bottles (≥2 L), a small amount of distilled water can be added to promote steam penetration.
2. Cooling and Storage: After sterilization, wait until the temperature drops below 60 °C before opening the door/removing the bottles.  Place them in a clean area or under laminar flow within 2 hours of removal; if not used immediately, loosely cover the bottle opening with sterile aluminum foil.
3. Reuse Limitations: Check for cracks and chips before each sterilization; soda-lime glass bottles can be sterilized repeatedly ≤10 times, borosilicate glass can be sterilized more times, but "individual bottle visual inspection + batch sampling" should still be followed.

Selection of Sterilization Methods for Glass Containers and Vials:
Injectables, Vaccines, Biological Products → Moist heat 121 °C/15 min or dry heat 180 °C/2 h (simultaneous depyrogenation).
Oral Liquids, Syrups → Moist heat sterilization is sufficient; if heat-sensitive components are present, change to "moist heat sterilization of bottles + sterile filtration of the liquid + aseptic filling".
Powders, Oils, Cream Bases → Dry heat sterilization (bottles) + subsequent aseptic powder filling.
Bottle Caps, Stoppers → Separate sterilization by moist heat or vH₂O₂, followed by in-line aseptic assembly.

Following the above specifications will ensure that glass containers and vials meet the pharmacopoeia and GMP requirements for "sterility assurance level (SAL ≤ 10⁻⁶)".