Sampling VOCs using DTD
This method was used by the Materials Working Group (MWG) Testing and Standards sub group for Round Robin Testing #2 in 2019 & 2020
developed by Indianapolis Museum of Art at Newfields
- Direct thermal desorption (DTD) should be performed in duplicate for all agreed‐upon Round‐Robin samples using the following DTD sampling conditions
Materials, Supplies, and Equipment[edit | edit source]
- Sample size for each trial should be noted and should fall between 3 and 20mg.
- Chromatographic separation should employ a DB‐5 chromatographic column (or equivalent) with a He carrier gas flow rate of 1.5 mL min‐1.
Procedure[edit | edit source]
- Trial 1: DTD at 90C for 30 minutes (only for those with with cryotrapping capability)
- Trial 2: DTD at 115C for 2 minutes (indicate cryotrap or no cryotrap)
- Trial 3: DTD at 180C for 1 minute (indicate cryotrap or no cryotrap)
- Split ratio of 20:1 is common.
- The oven temperature program is:
- 40C for 3 min
- 20C/min ramp to 150C
- 10C/min ramp to 250C
- isothermal hold for 6.5min.
- Detection of ions is accomplished using a mass spectrometer scanning a mass range of 29 to 120
m/z for the first 5 min to detect small volatile molecules
- Detection mass range of 45 to 450 m/z for the remainder of the analysis.
- Identification of volatile components is performed using the NIST14/Wiley Registry MS databases.
&Minor modifications to the analysis, specific to your method or process, should be noted (examples may include a change in split ratio, use of a glass wool plug, etc.)
- Participants should indicate if peak identification was performed manually using a NIST library orautomated using an integrated software approach.
- Once peaks are identified, some assessment of the material suitability should be made using ourapproved list of common pollutants. Refer to enclosed list, Compounds reported to damage cultural heritage objects.