Obvious CCI-Issue

Why isn't vacuum decay ideal for proving that vacuum is maintained in containers produced under vacuum?

Containers that need to maintain a vacuum—typically, this means a lyophilized (Lyo) product. If you know of other containers that require maintaining a vacuum, please share them in the comments for further discussion.

Vacuum maintenance and vacuum decay sound like a perfect match, don't they? In reality, they often aren't because vacuum loss usually occurs before the container is fully sealed.

Let's examine the production process: The freeze-drying cycle takes hours to days. To dry the product in the freeze-drying chamber, the stopper mustn't seal the vial completely. This is managed by using lyo stoppers, which are only partially pressed into the vial neck, leaving an opening inside the vial while maintaining stability during the process.

When primary and secondary drying are complete, the chamber is brought to the desired vacuum level—often with dry nitrogen—before the stoppering pressure is applied. Next, the shelves are narrowed, forcing the lyo stopper into the vial. In an ideal scenario, the vial is now sealed, and no gas exchange occurs, maintaining the vacuum. The chamber is then returned to atmospheric pressure to allow opening. The pressure inside the container is now lower than outside, which helps keep the stoppers in place.

The most critical phase for the Lyo product begins now: transferring the containers from the freeze dryer to the capping and crimping process. But why is this dangerous? Despite being in a clean room and having pressure differences supporting the closure, there's still a high risk of leaks. Any ingress of air with oxygen and moisture could alter the conditions under which the product’s shelf life was determined.

Next step: capping and crimping. Far more than 90% of containers that leaked before this step become sealed once the aluminum cap is applied. They are tight now, with few leaks, if any.

So, if you use a vacuum decay test now, what would you find? Correct—nothing! That’s why proving vacuum maintenance shouldn't rely on vacuum or pressure decay testing. Even the most sensitive helium leak test wouldn't work. There's no defect left to detect.

So, what can be done when even the most sensitive tests fail? The answer is to use the only test that detects changes in the gas phase: laser headspace technology, which can measure oxygen ingress.

We can help you with this and other CCIT decisions. More importantly, we can develop and validate a test method tailored to your needs. Contact us today to ensure a working method is in place by 2024!

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