Preliminary studies of using preheated carrier gas for on-line membrane extraction of semivolatile organic compounds

In this paper, we present results for the on-line determination of semivolatile organic compounds (SVOCs) in air using membrane extraction with a sorbent interface–ion mobility spectrometry (MESI-IMS) system with a preheated carrier (stripping) gas. The mechanism of the mass transfer of SVOCs across a membrane was initially studied. In comparison with the extraction of volatile analytes, the mass transfer resistance that originated from the slow desorption from the internal membrane surface during the SVOC extraction processes should be taken into account. A preheated carrier gas system was therefore built to facilitate desorption of analytes from the internal membrane surface. With the benefit of a temperature gradient existing between the internal and external membrane surfaces, an increase in the desorption rate of a specific analyte at the internal surface and the diffusion coefficient within the membrane could be achieved while avoiding a decrease of the distribution constant on the external membrane interface. This technique improved both the extraction rate and response times of the MESI-IMS system for the analysis of SVOCs. Finally, the MESI-IMS system was shown to be capable of on-site measurement by monitoring selected polynuclear aromatic hydrocarbons emitted from cigarette smoke. Figure Schematic of the MESI-IMS preheating carrier (stripping) gas system