Precision Thread Headspace - Vials now also for usage on PerkinElmer Turbomatrix Autosampler



Up to now Precision Thread Headspace-Vials have been mainly used on instruments with magnetic transport mechanism. The reason for this were the very hard to crimp magnetic crimp caps that made it necessary to find a more convenient and safer to handle sealing system. However, the risk of incorrectly and inconsistently crimped vials is generally connected to the crimping process which in the end may result in non-reproducible analysis results. On one hand this may be caused by different understandings of people how a correctly crimped vial should look like, but on the other hand may also be dependent on the design and condition of the used crimping tool (adjustability of crimping pressure, adjustability of crimping height, age of the tool and level of wear, etc.). Furthermore adjustment of a crimping tool - especially in Headspace - is not easy, as depending on the design of the crimp neck of the vial (bevelled top Headspace Neck / flat DIN Crimp Neck) and depending on the crimp neck’s and/or the septa’s thickness, crimping pressure as well as crimping height in the crimping head have exactly to be adjusted.

In order to eliminate these difficulties and risks, more and more instrument companies intend to make the sealing process of the sample vial - and connected to it, the tightness of the vial - safer and more reliable. PerkinElmer have now introduced the Precision Thread Headspace Vials in their delivery programme for all TurboMatrix 16, 40 and 110 autosamplers being built after 01.09.2006. Thus almost all common Headspace autosamplers (Agilent, CTC, Gerstel, PerkinElmer, Shimadzu, Varian) are now offering the option to use these universally suitable vials for Headspace + SPME. Another advantage of these closures is the much thinner septa in comparison to those used in crimp caps that are much easier and safer for the needle to penetrate.

New PRE-CUT septa for SPME applications

With the pre-cut septa technology further protection is especially offered to the SPME fibre. Here the Silicone layer is cut through in star shape, however, the PTFE lamination remains intact. As the Silicone part of the septa represents 95 per cent of the complete septa thickness, the needle can easily penetrate through the star shape for most of the septa’s thickness. The intact PTFE lamination will give 100 per cent sample integrity avoiding any contamination out of the silicone material. Besides the penetration support given by the pre-cut septa, there is also a very low number of fragmentation generated during the penetration process which is also very important in case of SPME. The star shape of the pre-cut was choosen, in order to give the needle a greater target area and the septa enough space to spread apart for penetration. The metal screw caps can be used even at high temperatures with appropriate temperature resistant septa and with their numerous threads press the septa tightly against the glass rims. Closed top screw caps are suitable for sample storage and transportation as well as replacement septa.

Here again the most important advantages summarized:

  • Reproducible results, without the variability of incorrectly crimped vials
  • Universally usable for Headspace and SPME
  • Tested with regard to tightness, penetration and magnetic force during transportation in the instrument
  • Out in the field, samples can directly be filled into the future analysis vial without the need of a later sample transfer in the lab
  • Much more convenient closure technique; no additional crimping tools necessary
  • Easy separation of vial and seal after the analysis
  • Safe penetration and better sealing than with crimp closures
  • 100 per cent sample integrity of the Pre-cut Precision Thread closure until the septa is pierced through
  • Star-shape gives the sensitive SPME-needle a greater target area for penetration and the septa enough space to spread apart
  • Low fragmentation which is important in SPME