Accurate results need a correctly crimped vial.
- Over-crimping may cause coring or poor septum re-sealing.
- Under-crimping can cause evaporation problems.
Correct crimping results in a cap that should not be able to rotate and a septum that appears smooth and level. This can be achieved with the proper adjustment of the vial crimpers.
Screw cap technique
In the same way that crimp caps can be over or under-crimped, screw caps can also be incorrectly tightened. Closures should be screwed on securely but not over-tightened.
Over-tightening may cause:
- Septum distortion – when placed under too much pressure the septum can become twisted inside the cap, leading to re-sealing problems and coring on injection.
- Unscrewing – an over-tightened cap can actually unscrew itself resulting in sample evaporation.