Introduction
Since inception of drug manufacturing, glass has been the material of choice for packaging pharmaceutical drug products. This is due to its protective qualities, impermeable characteristics and chemically inertness. In its pure state, glass, is made up of silicon dioxide with a melting point of roughly 1700°C; however, added modifiers and stabilizers are utilized to facilitate the production process and improve its durability.
Glass compositions cannot be considered as a stoichiometric chemical composition due to the variation within glass type, style and forming processes. Therefore, glass should be expressed over a range of different glass compositions which can produce different amounts of elemental impurities. It is critical to understand these impurities and what glass types produce specific amounts so the correct glass is utilized for a particular application.
Background
Glass containers are required to meet specific conditions of stability to be utilized for pharmaceutical applications. Glass is classified according to its resistance to chemical attack which is also known as hydrolytic resistance. This testing is outlined in USP chapter <660> and EP chapter 3.2.1. This experiment is meant to show the difference in elemental extractables of glass based on its type, style and forming process.
Experiment
An extractables profile was performed on a matrix of glass types in order to determine the amount of leachable elements from specific glass types. 20 mL samples were processed via an autoclave at 121°C for 60 minutes with high purity water. After the autoclave cycle the samples were transferred to polyethylene containers that were soaked overnight in a 10% solution of HCl and then rinsed with high purity water. The samples were immediately acidified with 3 drops of HNO3 for stabilization. A blank was made by adding 30 mL of high purity water to a polyethylene container and also acidified with 3 drops of HNO3. Inductively Coupled Plasma (ICP) analysis was then performed. Results are in parts per million (ppm).
Conclusion
- Increase of Sodium, Calcium and Silicon extractables in Type III glass
- Increase of Silicon in Tubular vial vs. Molded containers
In conclusion, glass compositions vary depending on several factors such as glass type, style and forming process. Therefore, it is critical to test the extractables profile of the glass container to ensure its success in a specific drug packaging application.