Screw Cap Vials are universal. Screwing the cap applies a mechanical force that squeezes the septum between the glass rim and the cap. Screw caps form an excellent seal and mechanically hold the septum in place during piercing. No tools are required for assembly.

screw cap vials supplier

Note on cap tightening: This is the mechanism that forms the seal and holds the septum in place during needle insertion. There is no need to over-tighten the cap, this can compromise the seal and lead to dislodging. The septum begins to cup or indent when you begin to over-tighten.

Crimp Vials squeeze the septum between the rim of the glass vial and the crimped aluminum cap. This forms an excellent seal preventing evaporation. The septum stays seated during piercing by the autosampler needle. The crimp cap vial requires crimping tools to carry out the sealing process. For low-volume settings, manual crimper tools are the choice. For high-volume settings, automated crimpers are available.

crimp vials with caps and hand crimper

Snap Cap Vials are an extension of the crimp cap system of sealing. A plastic cap is stretched over the rim of the vial to form a seal by squeezing the septum between the glass and the stretched plastic cap. Plastic has memory and wants to return to its original dimension. This tension in the cap to return to its original size is the force forming the seal between the glass, cap, and septum. The advantage of a plastic snap cap is no tools are required to assemble it. The snap-top cap is a compromise sealing system.

If the fit of the cap is very tight, they are hard to apply and may be subject to cracking.
If the fit is too loose, the seal is not very good, and the septa may be subject to dislodging.

Snap Cap Vials Supplier and manufacturer

Some more tips:

Based on our years of chromatography vial experience, crimp-cap vials are most situations best for GC and GC/MS analysis, while screw-cap vials are a better choice used for most HPLC and LC-MS applications. However, your personal preference and specific chromatography experiment requirements are also important factors to consider.

Snap Cap is fast to seal but sealing strength is not as good as crimp and screw vials. However, even though both types of crimp and screw vials have a good seal, crimp vials provide an additional guarantee of sealing for food, forensics, and other applications for which you want to avoid sample tampering. A crimping sealing is also recommended for the storage of volatile compounds.

For more knowledge about vial choosing, this article is also useful:

5 Points Need to Consider When Choosing An Autosampler Vial

5 Points Need to Consider When Choosing An Autosampler Vial

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