SEALING OF STERILE PREPARATIONS

E) Sealing

The container should be sealed in the aseptic area immediately adjacent to the filling machine. In addition to retaining the content of the sterile product, sealing of containers assures sterility of its contents. Temper-proof sealing is essential so as the sterility can be ensured until usage. Different approaches have been used for sealing of ampoules and the bottles.

Sealing of ampoules

The ampoules can be sealed either by tip or bead seal or pull seal. Both of the methods require heating with high-temperature oxygen flame. During sealing, the heating must be even and carefully controlled to avoid distortion of the seal. It is sometimes necessary to displace the air in the space within the ampoule above the product to prevent decomposition. This may be done by introducing a stream of inert gas, such as nitrogen or carbon dioxide, during or after filling with the product. Immediately thereafter, the ampoule is sealed before the gas can diffuse out. The tip seals are made by melting sufficient glass at the tip of the ampoules neck to form a bead of glass and close the opening. Thus, tip seal is also known as bead seals since a bead is formed during melting of the neck. Excessive heat of air and gases in the neck cause expansion against the soft glass with the formation of fragile bubbles at the point of seal. Open capillaries at the point of seal or cracks result in leakers. Fracture of the neck of ampoule often occurs during sealing if wetting had occurred at the time of filling, Also wet glass at the neck increases the frequency of bubble formation and contaminating deposits of carbon or oxides as a result of the effect of the heat of sealing on the droplet of the product. Pull seals are made by heating the neck of the rotating ampoule below the tip, then pulling the tip away to form a small, twisted capillary just prior to being melted closed. Pull sealing is a slower process, but the seals are more reliable than those from the tip sealing. Powder ampoules or other types having a wide opening must be sealed by pull-sealing.

With some sensitive products, it may be necessary to seal the ampoules with pull-seals to prevent combustion produces of the flame from entering the ampoule at the time of sealing, as might occur with tip-sealing.

Sealing of bottles, cartridges and vials

The closure is to be slide from a rotating or vibrating drum to the bottom of a chute, where it is positioned over a container ready for insertion by a plunger or some other pressure device which is followed by stoperring. To facilitate sliding of rubber closures, their surface is halogenated or coated with silicon which reduces the friction during slipping into the container’s mouth.

Aluminum caps are used to hold rubber closures in place. Single caps may have a permanent center hole or a center that is torn away at the time of use to expose the rubber closure. When applied, the bottom edge of the aluminium cap is bent (crimped) around and under the lip of the glass container. It cannot be removed without destroying the cap but perforation permit tearing away the portions of the cap to be discarded. Crimping can be achieved using the heavy duty crimping machines.