MS applications require very clean vials and closures, as this method of analysis is very sensitive to any kind of contamination. Therefore it was common up to now to only use silicone/PTFE septa in this field of chromatography as the purest available liner material. However, still most of the end-users experienced problems with even the highest grades of Silicone/PTFE septa due to ghost peaks arising from volatile siloxanes. Of course different treatments can reduce the level of these volatiles, but not eliminate the basic problem. La-Pha-Pack® now has therefore developed a one component 9mm Short Thread Cap that does not require any septa. This cap is inert and shows a similar chemical resistance like PTFE. Thus it can be used for sealing vials with all kinds of samples without loosing its inertness. Furthermore the cap is made out of a special material that is pierceable with all common types of HPLC and GC needles, as it has a thinned penetration area with a diaphragm. Although it has no septa, evaporation test have shown that it is liquid and gas-tight. Each manufactured batch is LC/MS and GC/MS controlled and supplied with an appropriate certificate. The certificate clearly states instrument, column and other method conditions being used for the test. Samples can be requested at service@la-pha-pack.com at any time.

With regard to penetration we would like to point out that in conjunction with this cap we would like to pronounce the recommendation of the following needle which is based on the results of Hamilton's research in this project.

Hamilton, Point Style 2 (Pst2):

22 (0.72x0.41), 22S (0.72x0.15), 23 (0.64x0.34), 23S (0.64x0.09)

Here again the most important advantages summarized:

• One Component Closure - no bleeding
• Cap is absolutely inert and shows a similar chemical resistance like PTFE
• Thinned penetration area with a diaphragm
• Even without a septa the vial is sealed liquid and gastight
• Each batch of caps produced is LC/MS and GC/MS controlled and supplied with an appropriate certificate