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Q&A with Schott Glass India


How can I protect my drug against light?

Certain drugs are sensitive to light especially the light in the area of 200 – 400 nm. This is e.g. true for the vitamins A, B, D, E, K and C. These drugs have to be packed in a special packaging that blocks the light from getting through. For glass packaging this is done by adding either Iron (Fe) and Titanium (Ti) to the composition or Iron and Manganese (Mn). They absorb the uv light ensuring the protection. Additionally the light transmittance can also be controlled by the wall thickness of the glass container. The thicker the wall is the less light goes through it. And another factor is the annealing oven. Here the temperature plays an important role. The higher the temperature is in the oven the darker the glass gets and the less light is going through.

I experience a pH shift with my drug solution. What is the reason and what can I do?

When glass gets in contact with an acidic or aqueous solution Hydrogen from the solution and Sodium from the glass are exchanging. This reaction leads to an elevated pH value. The amount of Sodium that is released into the solution also depends on the converting process. The more heat is used while forming the bottom of the container the more of Sodium Borates are evaporating from the glass. These Sodium Borates are condensing on the glass again and are being “burned” onto the glass again in the annealing oven. In the end they dissolve in the solution after autoclaving leading to a pH shift towards higher values. But also the ratio of glass inner surface to filling volume plays a role. Worst would be a 2ml container filled only with 0.5ml solution. The size of the container should be adjusted to the filling volume. There are some other smaller things that can be done. However, the mentioned ones have the biggest influence.

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