Determining the Residual Seal Force (RSF) on Medical Vials
Residual seal force (RSF) is the force with which the rubber stopper between the flanged cap and the neck of the vial is braced. This force measurement provides an indirect indication of the current integrity of the vial closure. However, these measurements must be correlated with established leakage tests.
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Container closure integrity tests:
There are two different tests for determining the integrity of primary packaging—container-closure integrity tests (CCIT)—which can be found in the PDA Technical Report Number 27, Pharmaceutical Package Integrity (2):
- Microbial immersion test
- Microbial aerosol challenge
- Bubble test
- Liquid tracer test
- Dye leak test
- Helium leak detection
- High voltage leak detection
- Corona discharge test
- Pressure/vacuum decay
- Vacuum retention
- Headspace Gas Analysis
The following methods should be prioritized:
The following methods should be prioritized over the highly popular dye test:
- Vacuum decay
- High voltage leak detection
- Laser-based headspace detection
USP 1207> This section contains guidance for integrity assurance of non-porous packaging intended for sterile pharmaceutical products.
Running the RSF test:
- Before the test, the safety cap must be removed from the closure
- The flanged cap holds the stopper under pre-load
- When a suitable compression load is applied to the rim of the flanged cap, it lifts from the neck of the vial. This is displayed as the reduction in force in the force travel diagram. The inflection point indicates the RSF value.
Sources:
Guidelines United States Pharmacopoeia USP 1207 | International Standards: ISO 8362-2 Annex C, ISO 3826-1 Annex C, ISO 15747 Annex C | PDA Technical Report Nr. 27 | FDA Guidance for Industry: Container and Closure System Integrity Testing in Lieu of Sterility Testing as a Component of the Stability Protocol for Sterile Products
ZwickRoell test fixture for determining the residual seal force
For testing the residual seal force of flanged caps, ZwickRoell recommends a device with inserts and compression dies of various sizes. The preload force of the rubber stopper on an aluminum flanged cap indicates the seal integrity of the vial closure.
- The test kit consists of a lower mounting platform for supporting the vial. An integrated prism centering aid with scale is used to read the vial diameter (6 mm to 70 mm) and
- The fixture is available with inserts and compression dies of various diameters (8.0 mm, 13.8 mm, 20.7 mm, 28.5 mm, 32.94 mm). For the respective test, the die diameter should correspond with the protective cap diameter.
- A modular design allows the various inserts to be changed quickly and easily.
- an upper compression test kit with locking nut for pre-positioning the die holds the compression die.
- Load is applied via a ball joint to compensate for deviations from parallel up to approximately 1°. All of the components are made of rust-free high-grade steel.
- It can only be used in conjunction with a safety device.
