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European Spectrometry Services Limited    |    Process, Research and Environmental Mass Spectrometers


The benefits of heated capillaries and how to fit them

Updated: Jan 12, 2023

What are heated capillaries and their benefits?

Our heated capillaries comprise a glass tube encased within a steel tube which is then encased in a heat resistant material. The Capillary can be used with or without heat applied.

When the heater is activated via the Capillary Heater Switch on your Mass Spectrometer, the steel tube heats and in turn heats the glass capillary. Heat will allow sample gases to flow more smoothly and prevent them from adhering to the sides of the capillary. This can be used in conjunction with our specially designed bake jacket and heated manifold (when provided), allowing high-temperature sampling.

The end of the capillary that has the heater plugs attached is pre-glued at our factory. This seals the Steel Tube and makes it gas tight. We allow 12mm of glass capillary to protrude from the Steel Tube. You can adjust the amount of capillary you require by several millimetres by carefully sliding the PTFE Ferrule up and down the Steel Tube.

The other end of the capillary is not glued. This allows flexibility in the tubes which aids fitting the capillary to your sample line. If both ends of the capillary were glued, the glass would break if the tubing was coiled.

It's important to keep in mind that the capillary is made of glass, so extra caution must be taken to avoid bending it too tightly or over-tightening the ferrules, as this can cause the glass to shatter.


How do I fit a heated capillary?

Follow the instructions below for easily fitting a new heated capillary. You can also refer to the video at the bottom for more help.

  • To begin, carefully unpack the capillary and remove any protective covers from the Tubing. Gently connect the end of the capillary, with the bullet crimps and fitted ferrule, to the mass spectrometer inlet port.

  • Securely attach the tube nut by tightening it with your fingers. Then, use a spanner to give it no more than a half-turn.

  • Connect the Heater Plugs to the Heater Sockets on the mass spectrometer.

  • With the first end properly secured, gently route the capillary to the sample point, ensuring that it is supported and not bent excessively. You will notice, once done, there will be an excess of glass protruding from the end.

  • Assess how much glass you require to enter your sample line connector. Normally 10 to 12mm from the end of the steel tubing is adequate.

  • Place the glass tube against a hard, flat surface and use a sharp Stanley knife to carefully cut away the excess.

Do not use a sawing motion This will bend the tube and it will snap.

When cutting, hold the knife at a 45-degree angle to the horizontal surface, apply downward pressure on your knife. The tube will cut easily.

  • Once you have cut the capillary to your desired length, you can proceed to fit the second tube and ferrule. Position the nut carefully and slide it into place. Thread the PTFE ferrule over the end of the glass and then the steel tubes.

Threading the ferrule over the steel will require a bit more force, but be mindful to avoid causing any damage to the capillary. The ferrule can be adjusted to achieve the desired length of the glass tubing by sliding it along the metal tube.

  • As you did before with the mass spectrometer end of the capillary, connect the other end of the capillary to the sample fitting, securing it finger-tight on the nut and then turning it no more than a half-turn with a spanner.

This equipment is now ready for use.

A heated capillary when received
A heated capillary as delivered


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