Preconcentration device for gas analysis

Frank James (1, 2, 3) , Philippe Breuil (1, 2, 3) , Christophe Pijolat (1, 2, 3) , Jean-Paul Viricelle (1, 2, 3) , El Hadji Malik Camara (4) , Danick Briand (4) , Axel Bart (5) , Ronan Cozic (5)

1 SPIN-ENSMSE - Centre Sciences des Processus Industriels et Naturels
2 PRESSIC-ENSMSE - Procédés et REactivité des Systèmes Solide-gaz, Instrumentation et Capteurs
3 LGF-ENSMSE - Laboratoire Georges Friedel
4 IMT - IMT Neuchâtel
5 SRA Instruments

In the field of analytical techniques, the preprocessing of the gases is generally a very important step, especially to get a preconcentration effect in order to increase the limit of detection. Concentrations ranges to detect are often lower than detection limit of many analyzers, leading to the needs of preconcentration devices. A gas mixture can flow through a microreactor and can be accumulated during a certain time thanks to a sorbent, and can be desorbed by a temperature pulse and brought to the detector. The current development of micro chromatograph needs a step of preconcentration. Microfabricated technology allows fabrication of miniaturized preconcentrator for this analytical detection system for in situ chemical analyzes. Main part of the device is a silicon microreactor (20*8,5mm², thickness 500μm) with a micro structuration made by deep reactive ion etching (DRIE) leading to a chamber with a volume of 14 µl. This device is usually filled with carbon powder as the adsorbent. The interaction between the sorbent and the gas is a physisorption reaction in order to not affect the analyte chemical structure. The adsorbent can also be the bulk like Porous Silicon (PS) which presents a high surface area and consequently interesting properties for the gas adsorption with weaker interactions, but lower desorption temperatures. A comparison between these two sorbent types is interesting in order to estimate their efficiency. A platinum resistance is screen printed on the back side of the silicon plate to act as a heater for the control of desorption temperature with a heating rate of 40°C/s. This allows adsorbed molecules to be released with a high concentration. An application for VOC is related to analysis in chemical plants. Experiments conducted with a carbon nanopowder preconcentrator associated to a micro chromatograph (μGC) with SRA Instruments Company have allowed to obtain preconcentration factors (ratio of outlet to inlet concentration) close to 800 with 50 ppb of toluene.

Mots clés: Micro-preconcentrator; sorbent; physisorption; VOC detection; silicon microreactor

Domaines: Génie des procédés

Frank James, Philippe Breuil, Christophe Pijolat, Jean-Paul Viricelle, El Hadji Malik Camara, et al.. Preconcentration device for gas analysis. IMRET13 (13th International Conference on MicroREaction Technology), Jun 2014, Budapest, Hungary. ⟨hal-01108516⟩