Direct desorption of volatiles from car trim
Direct desorption is useful to understand the total VOC and SVOC content of car trim, by exhaustive extraction of the volatiles from a small sample.
To analyse materials (solids, resins, pastes, emulsions, liquids) by direct desorption, samples are weighed directly into empty TD tubes or tube liners. They are then heated in a stream of inert gas to sweep volatiles from the sample matrix onto the focusing trap of the thermal desorber, for analysis by GC–MS in the usual manner (for example, using Markes’ UNITY or TD-100 thermal desorbers).
Direct desorption also facilitates selective concentration of the extracted compounds of interest, while water or other solvents can be purged to vent, thus simplifying analysis.
A commonly used method employing direct desorption is VDA 278 (Thermal desorption analysis of organic emissions for the characterization of non-metallic materials for automobiles). In this method, two tubes containing the same material are tested. One of these is desorbed for 30 minutes at 90°C, to detect VOCs up to n-C20, while the other is desorbed for 60 minutes at 120°C to detect SVOCs from n-C16 to n-C32.
- For an example of the use of direct desorption to detect VOCs and SVOCs from furnishings and car trim, see Application Notes 040 and 059.
- For a more in-depth discussion of standard methods relevant to in-vehicle air, see: M. Wensing, Standard test methods for the determination of VOCs and SVOCs in automobile interiors, in: Organic Indoor Air Pollutants, ed. T. Salthammer and E. Uhde, Wiley-VCH, 2009, pp. 147–161.
The following pages may also be of interest: