Thermal desorption – gas chromatography – mass spectrometry (TD-GC-MS)
Gas chromatography – mass spectrometry (GC-MS) is the golden standard for the analysis of (semi) volatile organic compounds (VOCs). Our GCMS-QP2010 Ultra (Shimadzu) is equipped with TD-20 thermal desorption unit (Shimadzu). For thermal desorption analysis, VOCs are collected (active or passive sampling) in sorbent tubes containing either a single or multi sorbent bed depending on the range of VOCs of interest.
Figure: The TD-GC-MS in the TDLab.
|
Sorbent |
Target VOCs |
|
Tenax TA |
Aromatics, apolars, polar compounds with a boiling point higher than 150oC, and semi-volatiles. |
|
Carbograph 5TD |
Light hydrocarbons (C3-C6) |
|
Carboxen 1000 |
Permanent gases and ultra-volatile hydrocarbons |
|
Sulficarb |
Thiols and very volatile organic compounds |
|
Quartz wool |
Semi-volatiles |
Since large volumes of air or headspace are collected in a smaller volume, VOCs are pre-concentrated. In the thermal desorption unit, VOCs are released from the sorbent by a flow of a heated inert gas. VOCs are then trapped again on a focussing trap for a second stage preconcentration to maximize sensitivity. In general, VOCs can be detected in the low part-per-billion volume (ppbV) range. Thermal desorption combined with GC-MS allows us to look at complex mixture and obtain confident identifications with the use of mass spectral libraries.
Examples of applications
- Breath biomarker discovery
- Environmental VOC analysis