Industry standard tubes - optimised for your application


Markes industry standard sorbent tubes (3½-inch (89 mm) x ¼-inch (6.4 mm) O.D.) are available in a range of materials to suit any application.  Mi offer unlimited versatility and unmatched expertise regarding sorbent selection and are happy to advise which combination of up to four sorbents per tube will best suit your monitoring requirements.

Download our application enquiry form now, for recommendations tailor made to your application.


All Markes tubes are supplied etched with a unique serial number to aid sample tracking and can be optionally etched with an additional 10 characters to aid identification.  Colour-banding of tubes is also available if required for rapid identification of tube-type – i.e. sorbent combination, date of packing, etc

Tube Types

Markes is pleased to offer the widest range of sample tubes for every possible monitoring application.  They are available in the following materials


Stainless steel tubes


Suitable for the vast majority of air monitoring and direct desorption applications, stainless steel tubes are compatible with both pumped and diffusive sampling and are also compatible with PTFE inserts for direct desorption of materials (liquid or solid)


Inert coated stainless steel tubes


Suitable for the analysis of labile / reactive compounds such as mercaptans, phosphorous pesticides, etc. inert coated stainless steel tubes are compatible with both pumped and diffusive sampling and are more robust than glass tubes. Compatible with PTFE inserts as above.


Glass tubes


Compatible with reactive compounds, system calibration and direct desorption of solid materials (but without PTFE inserts).  Glass tubes are compatible with pumped sampling and are available in the following configurations

  • Without frit - completely open tube
  • With a glass frit fitted 15 mm from the front (sampling) end of the tube for standard applications
  • With a glass frit fitted 30mm from one end of the tube for calibration purposes and direct desorption of materials. These tubes simplify liquid injection onto ‘calibration’ tubes and ensure materials remain in the middle of the heated zone during direct thermal desorption.



Empty tubes

Tubes may be supplied empty, for direct desorption of materials (with or without PTFE inserts where appropriate) or for packing with your own sorbents.


Pre-packed tubes

Packing thermal desorption tubes is a highly skilled and time consuming operation.  Loosely packed tubes may suffer sorbent movement and air space formation resulting in sampling errors.  Conversely, over compression of the sorbent bed will result in high tube impedance which may cause pump failure and / or inefficient thermal desorption.

Tubes may be supplied pre-packed with specific masses (or bed lengths) of up to four sorbents.  Available sorbents include a wide range of porous polymers, modified carbon blacks, carbonised molecular sieves and molecular sieves.  Other specialised sorbents are also available.  A packing report, detailing exact sorbent masses, is provided with each shipment of pre-packed tubes.

A tube re-packing service is also available.


Conditioned and capped tubes


Conditioning freshly packed sorbent tubes can take several hours per tube depending on the sorbents used and the monitoring application required.  Markes can supply pre-packed sorbent tubes which are pre-conditioned and capped with industry standard ¼-inch SwageLok-type caps with combined PTFE ferrules.


A tube re-conditioning service is also available.

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  • Either 3.5-inch (standard) or 4.5-inch (DAAMS*) tubes format
  • Compatible with electronic tagging (TubeTAG™) for recording tube history
  • Single platform for all TD applications
  • Sample re-collection(SecureTD-Q)for repeat analysis
  • Cryogen-free: Enhanced electrical cooling retains acetylene from up to 1.5L of air
  • Method compliant including stringent leak testing
  • Fully upgradeable to multi-tube, multi-canister, headspace and/or on-line automation
  • Optional electronic control of gas flows – split, desorb flow, etc. Aids method resettability and stabilises retention times
  • UNITY 2 adds to any commercial GC(MS) and is designed for easy maintenance
  • Time saving overlap mode allows desorption of a subsequent sample to begin while GC analysis of a previous sample continues.
  • * DAAMS: Depot Area Air Monitoring System as used in some chemical agent destruction facilities