A novel sample preparation technique, membrane extraction with a sorbent interface (MESI) has been optimized and used for continuous monitoring thermal degradation products in polyacrylonitrile (PAN) polymer headspace at different temperatures, followed by gas chromatographyâ mass spectrometry (GC-MS). MESI with a flat sheet poly(dimethyl siloxane)â polycarbonate (PDMSâ PC) membrane and Tenax trap was used. The system is very simple, fast and reliable and allowed us to extract, enrich and continuously monitor major volatile compounds released from the polymer at different temperatures. The volatile and semi-volatile gaseous degradation products were identified. Sensitivity of the method depends on the length of time for trapping.