In part two of this series on CCIT, two commonly used methods – Vacuum Decay and High Voltage Leak Detection – will be reviewed.
Vacuum Decay leak testing is based upon ASTM F 2338-09 “Standard Test Method for Nondestructive Detection of Leaks in Packages by Vacuum Decay Method”. This nondestructive test facilitates the identification of package leaks that may not be visibly detectable. It operates on the principal of vacuum decay. A test package is placed into a chamber that is subsequently exposed to vacuum. Sensitive pressure transducers monitor changes in chamber pressure; a result of package headspace being drawn through any leaks present. Using acceptance criteria established through method development, quantitative test results are qualitatively judged as pass or fail.
This type of testing is applicable to any package containing headspace, including, but not limited to, parenteral vial packages, screw-capped bottles, auto-injectors, and flexible bags or pouches. Vacuum decay is generally not recommended for liquid filled packages, as proteinaceous product has the potential to clog and mask leaks. However, if vacuum decay is the preferred method, alterations can be made to the method development and validation process to accommodate liquid filled packages.
Electrical Conductivity (HVLD)
The electrical conductivity leak test, also called high voltage leak detection (HVLD), or “the spark test”, is an approach for detecting leak presence and potentially the location of a leak(s) in the wall of a nonporous package, rigid or flexible, containing liquid product. The principle of leak detection is based on quantitative electrical conductance measurements. The presence of a leak path in the proximity of electrically conductive liquid results in a drop in test sample electrical resistance, as evidenced by a spike in current above a predetermined pass/fail limit. This highly sensitive method even works to detect package defects clogged by product formulation proteins or salts. Stability studies by clients have supported the use of this technology for nondestructive leak testing a variety of product formulation types. This should be considered, however, on a product-by-product basis.
Package systems that may be tested by HVLD include parenteral vials, pre-filled cartridges and syringes, plastic containers, and plastic bags or pouches.