Use of Solid-Phase Microextraction to Monitor Gases Resulting from Thermal Plasma Pyrolysis A.L.V. Cubas, E. Carasek & , N.A. Debacher, I.G. de Souza Departamento de Quı ´mica, Universidade Federal de Santa Catarina, Santa Catarina, 88040-900, Brazil; E-Mail: carasek@qmc.ufsc.br Received: 27 October 2003 / Revised: 18 December 2003 and 12 February 2004 / Accepted: 5 March 2004 Online publication: 30 June 2004 Abstract This paper proposes use of solid-phase microextraction to monitor the gases resulting from thermal plasma pyrolysis, instead of the traditional process using an air-tight syringe. The results confirm that thermal plasma technology can be used to eliminate carbon tetrachloride, because dioxins and furans were not detected. Some chlorinated compounds, for example tetrachloroethylene, hexachloroethane, 1,1,2,3,4,4 hexachloro-1,3-butadiene, 1,2,3,4,5,5- hexachloro-1,3-cyclopentadiene, and octachlorocyclopentadiene were detected, however. The results also confirm that this technique is more efficient than injection by means of an air-tight syringe for monitoring gases formed by the pyrolysis of carbon tetrachloride and enables detection of all viable sample constituents. Keywords Gas chromatography Solid-phase microextraction Organochlorine compounds Plasma torch arc Carbon tetrachloride pyrolysis Introduction Organochlorine compounds are charac- terized by their carbon-chlorine bonds and are a significant proportion of products used as solvents or reagents in the chemical industry. These compounds are a serious risk to organisms and the environment when disposed of inade- quately [1]. Although the best known technology for elimination of this class of compound is thermal incineration, for- mation of dioxins and furans, substances which are more toxic than the original material [1], render the process infeasible on a small scale. A promising alternative for destruction of residual of organo- chlorine compounds is pyrolysis by use of a thermal plasma. This method has important characteristics, for example use of high temperatures [2] and a highly reducing atmosphere which enable chemical reorganization, forming stable compounds. Several different studies report the treatment of organochlorine compound residues, including carbon tetrachloride [3, 4], by use of a thermal plasma [5–9]. Although they discuss torch efficiency and operating costs, and report the absence of dioxins and furans from the resulting pyrolysis gases, they give no details of the compounds formed by pyrolysis of these organochlorine com- pounds. Even at extremely high temper- atures and in highly reducing atmospheres such as those of the thermal plasma, decomposition of organochlorine compounds can lead to the formation of high-molecular-mass species. Dellinger and Taylor [10] proposed that chlorine facilitates condensation reactions result- ing in the formation of chlorinated aro- matic species. They suggested that the tendency to form high-molecular-weight species is attributable to the propensity of chlorinated radicals to undergo revers- ible, addition/elimination (displacement)- type molecular growth reactions. A kinetic study [11, 12] of the pyrolysis of CCl 4 in tubular reactors at temperatures up to 1273 K found evidence of the for- mation of solid carbon, Cl 2 , CCl 4 ,C 4 Cl 6 , and C 6 Cl 6 . These results indicate that reversible interconversion of these kinds of compound can occur at high temper- ature. The amounts of these new species formed in the thermal plasma can be very low, which makes them quite difficult to identify by use of conventional tech- niques. In the work discussed in this paper, therefore, the gaseous products from a thermal plasma were monitored by use of solid-phase microextraction [13–16], which seems to be an interesting alternative to other preconcentration procedures because it is based on the DOI: 10.1365/s10337-004-0337-2 2004, 60, 85–88 0009-5893/04/07 Ó 2004 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH Original Chromatographia 2004, 60, July (No. 1/2) 85