source temperature was 220 °C. MS Transfer Line temper-ature was 250 °C. Electron energy was 70 eV.
The above GC-MS analysis conditions were coupled with specific parameters developed for hexane extracts. The time of analysis was 55 min starting with heating at 70 °C for 5 min and then increasing the temperature at a rate of 5 °C/min to 230 °C, where it was maintained for 5 min. Scanning interval was 50–300 atomic units of mass (full scan), on splitless gas-flow mode. The period before fila-ment switch on was 4 min after injection of a 1 μl sample.
The mass spectra library NIST 2.0 of the National Insti-tute of Standards and Technology, USA was used for com-pound identification. In particular, acetophenone was identified by comparison between the mass spectra recorded for hexane extracts and the mass spectra from the NIST library. The probability of adequate identification was assessed to be 90–99 %.