Selection Method Of Sample Vial
The sample vial is small, but the knowledge is great. When there is a problem with our experimental results, we always think of the vial at the end, but it is the first step to consider. When choosing the right vial for your application, you need to make three decisions: the septum, the lid, and the vial itself.
01. Septum Selection Guide
• Recommended for a single injection
• Excellent solvent resistance and chemical compatibility
• Will does not reseal after the puncture
• Not recommended for long-term sample storage
PTFE / silicone
• Recommended for multiple injections and sample storage
• Excellent resealing characteristics
• It has the chemical resistance of PTFE before puncturing, and the septum will have the chemical compatibility of silica gel after puncturing
• Operating temperature range is -40 ℃ to 200 ℃ pre-cut PTFE / silicone
• Provide good ventilation to prevent the formation of a vacuum in the sample vial, so as to achieve excellent sampling reproducibility
• Eliminate the clogging of the bottom needle after sampling
• Good resealing ability
• Recommended for multiple injections
• Operating temperature range is -40 ℃ to 200 ℃ without spacer PE
• Has the same advantages as PTFE
02. Vial cap guide
There are three types of caps for sample vials: jaw cap, bayonet cap, and screw cap. Each sealing method has its own advantages. Clamp jaw cover squeezes the septum between the edge of the glass sample bottle and the folded aluminum cover. The sealing effect is very good, which can effectively prevent the sample from evaporating. When the needle of the autosampler pierces the sample, the position of the septum remains unchanged. A capping device is required to seal a vial with a crimp cap. For a few samples, a manual crimper is the best choice.
For a large number of samples, an automatic crimper can be used. Bayonet cover is an extension of the jaw cover sealing method. The plastic cap that fits over the edge of the vial forms a seal by squeezing the septum between the glass and the stretched plastic cap. This tension creates a seal between the glass, bottle cap, and septum. The plastic bayonet cover can be closed without any tools.
• The sealing effect of the bayonet cap is not as good as the other two sealing methods.
• If the fit of the bottle cap is very tight, the bottle cap is difficult to close and may break.
• If it is too loose, the sealing effect is poor, and the septum may leave the original position. Screw cover is universal. Tightening the cap will exert a mechanical force, squeezing the septum between the glass rim and the aluminum cap.
During the piercing and sampling process, the screw cap has an excellent sealing effect and mechanically bears against the septum. No tools are required for assembly. The PTFE / silicone septum of the screw cap is fixed on the polypropylene bottle cap by a non-solvent bonding process. The design of the bonding technology is to ensure that the septum and the cap are always together during transportation and when the cap is mounted on the sample bottle.
This adhesion helps prevent the septum from falling off during use, but the main sealing mechanism is still the mechanical force applied when the cap is screwed onto the sample vial. The mechanism of screwing the cap is to form a seal and keep the septum in the correct position during the insertion of the sampling needle. There is no need to over-tighten the cap, otherwise, it will affect the seal and cause the septum to fall off and translocate. If the cap is tightened too tightly, the septum will become cup-shaped or dent.