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Caps and Seals
Closures are the already assembled combination of the cap and sealing disc. In order to carry out a correct analysis, it is important that the seal is also inert and uncontaminated, in addition to the sample bottle. Various closures, such as snap ring, roller edge, flanging or screw caps, are available for the sample bottles. In addition to the suitability of sample bottle and closure for the used autosampler, the personal preferences in handling are also decisive. Can the flanging or screwing of the vials be better integrated into the working process? Should the closed bottle be opened quickly and easily?
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Choice of the appropriate closure depending on the type of bottle
Depending on the type of bottle used, the appropriate closure must be selected:
- Screw caps: Open (for use with various septa) or closed (for sample storage)
- Short thread caps: Open (for septa use) or closed (for sample storage)
- UltraBond screw caps: For ND9 and ND24; The caps and septums are inextricably linked.
- Flanging caps: With the septum ready assembled
- Headspace caps: Safety caps for headspace analyzes with a predetermined breaking line, in order to avoid bursting of the bottle if the internal pressure is too high.
- Snap-on caps: Hard or soft polyethylene; Only open (for use of septa)
- The short thread and crimp caps are also available in magnetic design for the respective car samplers (e.g., CTC).
Fluorine-free septa and PP vials for PFAS analysis
Fluorine-free septa are ideal for PFAS analysis or the analysis of fluorinated / halogenated organic compounds. Macherey-Nagel caps and septa suitable for PFAS analysis are made of PP or PE. They feature a polyimide coating instead of a PTFE lamination as a chemical resistant barrier on the silicone carrier material. This prevents the migration of fluorine into the sample. The silicone carrier material is of high analytical purity and easy to penetrate. You can choose from fluorine-free ND 9 screw caps and ND 11 snap ring caps. In the snap ring closure, the septum is mounted in a soft snap ring cap which can be easily pressed onto the bottle or removed.
Also, for PFAS analysis vials made of polypropylene should be used: The adsorption effects are lower with plastic bottles than with glass bottles or even silanized glass bottles.