In part three of this series on CCIT, two commonly used methods – Helium and Mass Extraction – will be reviewed.
Helium Mass Spectrometry
Helium mass spectrometry, based upon ASTM F 2391-05 “Standard Test Method for Measuring Package and Seal Integrity Using Helium as the Tracer Gas” is applicable to non-porous packaging such as vials, syringes, and cartridges. Even flexible packages can be tested by helium mass spectrometry using appropriate test fixture.
Helium-filled samples are placed in a test chamber, where a vacuum is created by the instrument’s internal pumps. Leaking samples allow helium to escape, enter the test system, and be detected by an analyzer cell. The stream of helium ions hitting the analyzer cell target is proportional to the partial pressure inside a sample. From this, a specific leak rate can be calculated and reported to the user. Results can be reported quantitatively (as a leak rate), or qualitatively (Pass or Fail) if method development is performed.
This type of testing may be of interest to clients looking to accurately assess the performance of an established package or analyze the effect of processing variables, such as capping force, closure materials, etc., on the performance of a package system.
Mass extraction leak detection operates by drawing vacuum on a sample enclosed in a chamber. Once vacuum is established, the instrument monitors the amount of airflow required to sustain a specific vacuum level. The amount of flow required to keep the vacuum steady is equal to the amount of flow escaping from leaks in sample under testing. Specific test parameters must be set after adequate method development. Results are reported quantitatively, as flow rates, as well as qualitatively (Pass or Fail) according to acceptance criteria established in method development.
Mass extraction testing is applicable to any package containing headspace, including parenteral vial packages, screw-capped bottles, and flexible bags or pouches. In some cases, liquid-packages can also be leak tested by this approach if the product formulation poses no threat of clogging leak paths.