Direct Thermal Desorption

Hyphenation On-line GC, HPLC, SPE-SFE, SFE-SPE GC (most common), HPLC. Direct thermal desorption. 

In a study on the identification of organic additives in rubber vulcanisates using mass spectrometry, Lattimer et al. [22] used direct thermal desorption with three different ionisation methods El, Cl and FI. Also, rubber extracts were examinated directly by four ionisation methods (El, Cl, FD and FAB). The authors did not report a clear advantage for direct analysis as compared to analysis after extraction. Direct analysis was a little faster, but the extraction methods were considered to be more versatile. 

Direct mass analysis of additives in bulk polymers is in principle an attractive methodology, albeit with many restrictions (Table 6.38). Early MS work has focused on direct thermal desorption of additives from the bulk polymer, followed by EI-MS [22,240], CI-MS [22,63] and FI-MS [22]. However, these traditional approaches are limited to polymer additives that are both stable and volatile at the higher temperatures,... 

Relatively few descriptions of direct mass spectral analysis of plastics compounds have appeared in the literature [22,37,63,240,243], Additives in PP were thermally desorbed into a heated reservoir inlet for 80 eV EI-MS analysis [240], Analysis of additives in PP compounds via direct thermal desorption ammonia CI-MS has been described [269] and direct mass spectrometric oligomer analysis has been reported [21],... 

Identification of the Volatile and Semi-Volatile Organics in Chewing Gums by Direct Thermal Desorption. John J. Manura, Scientific Instrument Services, Inc., Short Path Thermal Desorption—Application Note No. 12 — October 1992, http //www.sisweb.com/referenc/applnote/ap12-a.htm... 

These liner exchange systems make feasible yet another analysis mode direct thermal desorption (DTD). Here the liner or an insert is packed with the solid sample. The liner exchange system can then be used in place of a conventional autosampler. The liner is automatically inserted into the PTV and the volatiles thermally desorbed onto the column. Some analysts may feel uneasy about such desorption from the solid phase how does one know that all of the volatile analytes have been released from the sample crystal lattice However, where applicable, this approach may not be as difficult to validate as one might imagine. For instance, the PTV can be cooled after the analyte transfer, and then, at the end of the chromatographic temperature programme, reheated to repeat the process. Ideally all of the analyte should transfer in the first cycle and none in the second, demonstrating that complete desorption occurs in the method. 

Oezel, M.Z., Goegues, R, Lewis, A.C., (2006) Determination of Teucrium chamaedrys volatiles by using direct thermal desorption-comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry. J. Chromatogr All 14 164-169. 

Ozel, M.Z., Gogus, R, Hamilton, J.E, Lewis, A.C. (2004) The essential oil of Pistacia vera L. at various temperatures of direct thermal desorption using comprehensive gas chromatography with time-of-flight mass spectrometry. Chromatographia 60 79-83. 

The high temperatures used for direct thermal desorption/extraction. Note that emissions testing is conventionally carried out at room temperature (Table 6.2) whereas VDA Method 278 for example requires desorption temperatures of 90 and 120 °C for volatiles and fogging compounds respectively. 

Direct thermal desorption is usually carried out on bulk samples, that is, with emissions from multiple surfaces rather than just one exposed surface. 

Direct thermal desorption is normally limited to relatively small sample sizes (<1 g) which may not be representative of the product/material as a whole. 

Aroma compounds from vanilla beans have been extracted using several extraction procedures, using alcohols and organic solvents (Galletto and Hoffman, 1978 Dignum et al., 2002), direct thermal desorption (Hartman et al., 1992 Adedeji et al., 1993) and solid-phase microextraction (SPME) (Sostaric etal., 2000), followed by identification of the compounds by gas chromatography-mass spectrometry (GC-MS). 

Adedeji et al. (1993) used a direct thermal desorption technique (220°C) to analyse the volatiles from beans that might cause the thermal degradation and transformation of sugar into common volatile compounds such as 3,5-dimethyl-2,4(3H,5H)-furandione and 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one. This last compound was detected at a high concentration (3880 ppm) in Mexican vanilla, being the third most abundant compound after vanillin and 2-furfural, and far more abundant than vanillic acid, p-hydroxy-benzaldehyde or p-hydroxybenzoic acid. 

C. C. Grimm S. W. Lloyd J. A. Miller A. M. Spanier, The Analysis of Food Volatiles Using Direct Thermal Desorption. In Techniques for Analyzing Food Aroma R. Marsili, Ed. Marcel Dekker New York, 1997 pp 59-79. 

Perez-CoeUo, M. S., Sanz, J., Cabezudo, M. D. (1997). Analysis of volatile components of oak wood by solvent extraction and direct thermal desorption-gas chromatography-mass spectrometry. J. Chromatogr. A, 778, 427 34. 

Schnelle-Kreis, J., Orasche, J., Abbaszade, G., Schafer, K., Flarlos, D.P., Hansen, A.D.A., Zimmermann, R. Application of direct thermal desorption gas chromatography time-of-flight mass spectrometry for determination of non-polar organics in low-volume samples from ambient particulate matter and personal samplers. Anal. Bioanal. Chem. 401, 3083-3094 (2011)... 

Cadwallader and Shahidi (82) identified the potent odorants of seal blubber oil by direct thermal desorption-gas chromatography-olfactometry (DTD-GCO). In... 

Thermal Desorption (direct) Direct thermal desorption from sample located within the injection port finer (see discussion below). ... 

Sies, A., Hirsch, R., Ldscher, R., Tablack, R, Guth, H., Direct thermal desorption and FAST-GC-TOF-MS for a rapid quality control of hazelnuts, in Flavour Research at the Dawn of the Twenty-first Century, Rroceedings of the 10th Weurman Flavour Research Symposium Beaune, Le Quere, J.L., fitievant, R.X. (Eds.), London/Raris/New York, Lavoisier and Intercept 2003... 

If the target analytes do not readily evaporate from the matrix they are in, then another recently improved technique - direct thermal desorption - is more effective. This is often used for dry, non-volatile matrices like wood, soil, spices or resins. The sample is placed directly in the liner or desorption chamber, which is then flushed with inert carrier gas and heated rapidly to transfer the volatiles to the analytical column. 

Hartman T.G., Lech J, Karmas K., Salinas J., Rosen R.T. and Ho C.T. (1993) Flavor characterization using adsorbent trapping-thermal desorption or direct thermal desorption-gas chromatography and gas chromatography-mass spectrometry. 16 th I FT Basic Symp. Ser., New-Orleans, June 19-20, 1992. Ho Manley, Eds Flavor Measurement. Marcel Dekker, New York, pp. 37-69. 

Characterization of olive oil volatiles by multi-step direct thermal desorption-comprehensive gas chromatography-time-of-flight mass spectrometry using a programmed temperature vaporizing injector. Journal of Chromatography A, Vol.1186, pp. 228-235, ISSN 0021-9673... 

Ozel, M.Z. Gogus, F. Lewis, AC. (2006). Comparison of direct thermal desorption with water distillation and superheated water extraction for the analysis of volatile components of Rosa damascena Mill, using GCxGC-TOF/MS. Analytica Chimica Acta, Vol.566, pp. m- T7, ISSN 0003-2670... 

Schnelle-Kreis, J. Welthagen, W. Sklorz, M. Zimmermann, R. (2005). Application of direct thermal desorption gas chromatography and comprehensive two-dimensional gas chromatography coupled to time of flight mass spectrometry for analysis of organic compounds in ambient aerosol particles. Journal of Separation Science, Vol.28, pp. 1648-1657, ISSN 1615-9314... 

Garcia, M.A. Sanz J. (2001). Analysis of Origanum vulgare volatiles by direct thermal desorption coupled to gas chromatography-mass spectrometry. Journal of Chromatography A, Vol.918, No.l, (June 2001), pp. 189-194, ISSN 0021-9673... 

Gogus, F. Ozel, M.Z. Lewis A.C. (2006). Analysis of the volatile components of cheddar cheese by direct thermal desorption - GCxGC-TOF/MS. Journal of Separation Science, Vol. 29, No. 9, pp. 1217-1222, ISSN 1615-9306... 

Akoto, L. SteUaard, F. hth, H. Vreuls, R.J.J. Pel, R. Improved fatty acid detection in micro-algae and aquatic meiofauna species using a direct thermal desorption interface combined with comprehensive gas chromatography-time-of-flight mass spectrometry. J. Chromatogr. A, 2008, 1186, 254-261. 

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