Materials and Reagents

1. Acetonitrile (gradient grade)
   
2. Methanol (gradient grade)
   
3. Nitrogen (gaseous)
   
4. Scentless soap (Labosol S)
   
5. Argon (gaseous)
   Note: Argon provides a clean, inert atmosphere which is heavier than air, for long-term storage of conditioned ST pieces. For shorter time periods, storage under nitrogen is adequate.
   

Equipment

1. Silicone laboratory tubing (ST, 1 mm i.d. x 1.8 mm o.d.) (Carl Roth, catalog number: 9555.1 )
   
2. 4 ml screw-neck glass vials (brown) (Macherey-Nagel, catalog number: 702973 ) and screw caps (N13 PP) (Macherey-Nagel, catalog number: 702051 )
   
3. 1.5 ml screw-neck glass vials (Macherey-Nagel, clear, catalog number: 702282 ; brown, catalog number: 702293 ) and screw caps (N9 polypropylene [PP], Macherey-Nagel, catalog number: 702028)
   
4. Polytetrafluoroethylene (PTFE) seal tape (RS, catalog number: 231-964 )
   
5. Paddle wire
   
6. Retractable-blade utility knife or single-edged razor blade
   
7. Cutting mask (custom-made) for uniformly cutting 5 mm PDMS pieces, made out of polyoxymethylene (POM) (Figure 1A)
   Note: PDMS pieces can also be cut manually, but a cutting mask increases uniformity and saves time when cutting large numbers of PDMS pieces.
   
8. Laboratory borosilicate glass bottle (volume: 100-250 ml) (Carl Roth, catalog numbers: A358.1 or A359.1 )
   
9. Stainless steel spatula (Carl Roth, catalog number: 1902.1 )
   
10. Stainless steel forceps (Carl Roth, catalog number: 2687.1 ) and aluminum foil (Carl Roth, catalog number: 0192.1 )
    
11. Glass column (50 ml) with screw-cap ends, containing a size P0 glass frit (Figure 1C)
    Note: The glass frit should be sufficiently small to cause a turbulent nitrogen gas flow.
    
12. Polyether ether ketone (PEEK) screw-caps with PTFE lining and stainless steel hose connections, for glass column (Figure 1D)
    
13. Flow meter (5-10 L volume)
    
14. PTFE gas hoses
    
15. Heating oven (max. temperature at least 210 °C)
    
16. Polyethylene tetraphthalate (PET) trapping containers (30-600 ml, Solo or Iso-pack)
    Note: The trapping container volume should be as small as possible without significantly changing environmental conditions (e.g. humidity, temperature). This can be tested by enclosing a test sample for the planned trapping period and checking for any visual change (e.g. wilting, condensation) as well as by placing environmental sensors (e.g. temperature, humidity) inside and outside of the trapping container.
    
17. Thermo desorption (TD) unit (Shimadzu, model: TD-20 )
    
18. 89 mm TD sampler tubes (Supelco, catalog number: 28714-U ) and caps with O-rings (Shimadzu, caps, catalog number: 2235461791 and O-rings, catalog number: 2235716691 )
    Note: Caps can also be milled from brass as long as the exact dimensions are kept.
    
19. GC-MS (Shimadzu, model: GC-MS-QP2010Ultra )
    
20. 5MS GC column (30 m long, 0.25 mm i.d., 0.25 µm film thickness) (Restek Rtx-5MS)
    
21. WAX column (30 m long, 0.25 mm i.d., 0.25 µm film thickness) (Phenomenex ZB-Wax Plus)
    

Procedure