Integrity testing of foil pouches offers a unique set of challenges. In most packaging processes that involve foil as the product barrier, there is a concern about the incidence of punctures in the foil. These defects (typically called micro-voids) can be created as the foil is being rolled into thin sheets and tiny particles are inadvertently rolled into the foil. The most common defect is caused from the handling of the packages during the assembly of the foil and insertion of the drug product.
These defects are difficult to see as the human eye can only reliably see punctures that are larger than 100 µm. Punctures smaller that this can pose significant concern for ingress and as such, can alter the efficacy of the product.
The sensitivity of a helium leak test method offers an ideal platform for quality control testing of foil-based package systems. In much the same way that blister cards would be leak tested, the test method relies on detecting helium sealed in the package system as it escapes through micro-voids in the pouch. A test sequence begins by placing the foil pouch in the custom designed test fixture and drawing a vacuum. The resulting pressure differential causes helium to escape through potential defects in the package. While under vacuum pressure, flow is directed to the analyzer cell where any escaping helium gas is quantitively measured in the cell. Typical test cycle times range from 20 – 60 seconds. Once the test cycle is completed and measurement is recorded, the test chamber is vented to atmosphere and a new sample can be tested. Upon completion of testing for all samples in the defined set, each pouch's helium concentration value is measured by using the HSAM helium concentration device. This process normalizes the helium leak rate to 100% thereby allowing direct comparison of all test samples along the production line set-up.
