A fast thermal desorption unit for micro thermal desorption tubes, Part I: Development of the system and proof of concept measurements with hyper-fast gas chromatography.

A system consisting of a thermal desorption unit (TDU) and micro thermal desorption tubes (μTD-tubes, 1.4 mm I.D., 10mg Tenax TA) for fast desorption of analytes was developed for the efficient combination of hyper fast gas chromatography with thermal desorption. The fast desorption is achieved by a significantly reduced thermal mass compared to conventional thermal desorption tubes. Therefore, extremely fast heating and cooling cycles are possible. Proof of concept measurements combining the new setup with a flow-field thermal gradient gas chromatograph (FF-TG-GC) and FID detection show good precision and linearity with R≥0.995 in the analysis of an n-alkane mix (C-C). Thermal desorption occurs within 12s. The impact of reduced μTD-tube dimensions on desorption time, full width at half maximum (FWHM), breakthrough volumes, tube flow rates ergo linear velocities, porosity and back pressure is discussed.