2.4. Identification and quantification of volatile compounds
The equilibrium concentration of carvacrol (main component of oregano essential oil) and citral in the polymer samples was determined by thermal desorption and GC analysis using a thermal-desorber connected in series to the gas chromatograph. In brief, a portion of the tested film (ca. 1 cm2) was placed in the desorption cell and heated at 210 °C for 7 min. A He gas stream carried the desorbed compounds to the GC through a transfer line heated at 230 °C. The GC was equipped with a 30 m, 0.53 mm, 2.65 μm Agilent HP-1 semicapillary column. The chromatographic conditions were: He as the carrier gas, 210 °C and 260 °C injector and detector temperatures, 7 min at 45 °C, heating ramp to 220 °C at 18 °C/min, and 12 min more at 220 °C. At the end of the desorption process the sample was weighed with a 0.1 mg precision balance Calibration was done by injecting known amounts of carvacrol or citral in the desorption cell.