Skip to main content
Shopping bag
Sampling Technologies

Tubes - sorbent tubes for TD

Pre-packed thermal desorption tubes are used to monitor VOCs, VVOCs and SVOCs. Compounds of interest are adsorbed onto the sorbents in the tube during active or passive sample collection, and subsequently desorbed by a thermal desorption system for analysis by GC–MS. Choose industry-standard tubes with our tube selector.

Industry-standard tubes (3½″ × ¼″ o.d.) are compatible with Markes, PerkinElmer, Shimadzu, Dani, CDS and Gerstel 3.5+ thermal desorption (TD) systems. All Markes’ sorbent tubes are permanently labelled with a unique serial number, barcode and sampling flow arrow for easier use and tracking.

Tubes can be packed with a single sorbent bed for active or passive sampling, and multiple sorbent beds for active sampling of an extended hydrocarbon range. Tubes are sold conditioned and capped (with brass long-term storage caps) for immediate use on arrival or can be supplied unconditioned for analysts with their own means of conditioning.


Sorbent tubes are available in three materials: stainless steel, inert-coated stainless steel and glass. Inert-coated tubes are a robust alternative to glass tubes for sampling thermally labile and reactive compounds. Markes is an approved partner of SilcoTek, who treat the entire surface of the tubes with their industry-leading SilcoNert™ coating. This eliminates surface adsorption of active compounds and avoids the breakdown of thermally labile analytes during analysis.

Markes operates under stringent quality controls – our tubes are packed to a tolerance of ±2.5% by weight or better. We have designed a range of method-compliant, application-specific and general-use sorbent tubes to simplify method development.

Types of sorbent tube

  • Method-specific – Single-bed and multi-bed tubes to suit specific methods such as EPA TO-17 and US EPA Method 325. Purchased pre-conditioned, they minimise preparation time and provide confidence in results.
  • Application-specific – Single-bed and multi-bed tubes optimised for specific applications such as bio-monitoring, material emissions testing, air sampling in hydrophobic environments and SVOC monitoring. Optimised by TD experts to streamline method development and minimise downtime.
  • Single-sorbent – Packed by TD experts using optimised mesh sizes, bed lengths and packing methods for pumped and passive sampling.
  • Multi-bed – Popular tubes packed with multiple sorbent beds: typically, two or three. Optimised combinations of mesh size, mass and sorbent combinations for effective pumped sampling. Allow for sampling of extended analyte ranges on a single tube, reducing costs and simplifying workflow.
  • Custom – Custom-packed single-sorbent or multi-bed tubes specifically configured to suit your requirements. Further options include custom laser-etching, banding and RFID-tagging (TubeTAG™).
  • SafeLok™ tubes – With diffusion-locking SafeLok options for additional peace of mind, or for sampling at low flow rates.