Solid Phase Microextraction Analysis of the Gliding Arc Discharge Products

This work was focused on the studies of gliding arc plasma discharge with respect to its use in decomposition of volatile organic compounds and on the solid phase microextraction analysis of the discharge products. The simple one stage gliding arc reactor was used for these experiments. The applied voltage generating the discharge was varied in the range of 3.5 – 4 kV, the dry air and its mixtures with nitrogen, oxygen and argon were used as carrier gas, with flow rate of 1000 – 1600 ml/min. The toluene was used as a model VOC and its maximal decomposition of 73 % was achieved at the oxygen content in carrier gas of 60 %. For measurements with air as a carrier gas, the maximum decomposition efficiency was 68 %. The exhaust gas was sampled during these experiments by solid phase extraction technique (sorption tubes) and analyzed by gas chromatography linked to the mass spectrometry. The other part of study was focused on the applicability study of solid phase microextraction technique for the gliding arc discharge products sampling. The discharge exhaust gas was sampled by three different kinds of SPME fibres and the product’s analysis was done by GC-MS. The experimental results obtained by the destruction of cyclohexane and toluene as the model VOC compounds showed that this sampling technique can be used for the simple and cheep qualitative analysis of the discharge products. The results showed that the fiber coated by Carbowax/divinyl-benzene (CW/DVB) can extract the highest number of destruction products independently on the used VOC representing compound. The Carboxen/polydimethylsiloxane/divinylbenzene (CAR/PDMS/DVB) fiber is useful for the oxygen containing compounds and its use will be recommended especially when the destruction is done in the air enriched by oxygen. The applicability of the polydimethylsiloxane (PDMS) fiber is strongly limited. Introduction Gliding discharge is an interesting possibility to generate a nonthermal plasma discharge at atmospheric pressure [1]. In fact, theoretical models determine that gliding arc combines both thermal and nonthermal plasmas, but up to the 75 % of the total energy can be delivered in the nonthermal part of the gliding arc discharge [2]. This offers high energy efficiency and selectivity for chemical reactions. The excitation energy can be transported to specific molecules in the reacting gas mixture. Recent studies showed that the reaction stimulation efficiency by the gliding arc discharge plasma is very high [1, 3]. This work is focused on the studies of gliding discharge with respect to its use in the decomposition of volatile organic compounds (VOC). Analysis of the discharge products proceeded in a gas chromatograph linked to mass spectrometer. The main advantage is a connection of separation and identification technique. There is no need for time-consuming analytical separations. At first, the products of decomposition were adsorbed on active coal in the sorption tubes and then extracted to carbon disulphide. This part of our work was focused on decomposition efficiency of toluene and searching for the optimum decomposition conditions. The second part of the experiments was aimed at the analysis of the Gliding arc discharge products sampled by Solid Phase Microextraction (SPME). We tested the SPME technique suitability for the discharge exhausts gas qualitative analyses and if this technique can be used also for the quantitative estimations of various discharge products. WDS'05 Proceedings of Contributed Papers, Part II, 423–428, 2005. ISBN 80-86732-59-2 © MATFYZPRESS