Gas chromatography-mass spectrometry. Samples were analyzed by gas chromatography using a HP6890 instrument coupled with a HP 5973 mass spectrometer. The gas chromatograph is equipped with a split-splitless injector and a Factor FourTM VF-35ms 5% fenil-methylpolysiloxane, 30 m, 0.25 mm, 0.25 μm film thickness capillary column. Gas chromatography conditions include a temperature range of 50 to 250°C at 40°C/min, with a solvent delay of 5 min. The injector was maintained at a temperature of 250°C. The inert gas was helium at a flow of 1.0 mL/min, and the injected volume in the splitless mode was 1 μL. The MS conditions were the following: ionization energy, 70 eV; quadrupole temperature, 100°C; scanning velocity, 1.6 scan/s; weight range, 40-500 amu.