Crimp closures are generally known for excellent sealing characteristics even when it comes to long-term sample storage.

Check out the available crimpers here at https://www.sentori.com.my/product-category/86/vial 
 

1. Is the vial properly crimped?

Check if:
 
• The cap surface is flat.
• The sides of the cap fit tightly around the vial neck and do not show any deformations.
• The septa is not being sucked into the vial nor does it emerge out of the centre hole.
 
WHEATON® E-Z Crimpers
 
Our WHEATON® E-Z Crimpers provide a manual stop that can be adjusted to provide a reproducible endpoint when the crimper handles are closed.
 
For lower crimping pressure, turn the adjustment screw (1) clockwise.
For higher crimping pressure, turn the adjustment screw (1) counter clockwise.
 
The setting of the screw can be fixed by using the adjusting screw lock nut (2).