.The mass detector was a simple quadrupole MS (Thermo
Electron MD 1000, France). Spectra were obtained by electron
ionisation (EI), under positive (CI+) and negative (CI−)
chemical ionisation conditions. The source conditions for EI
were 70 eV electron energy and the temperature was programmed
from 60 to 600 ◦C at a rate of 65 ◦Cmin−1. The
reference temperature was 300 ◦C. Data were collected over
a mass range of 15–500 uma using a 0.90 s scan time and
a 0.10 s interscan delay. For CI, methane was used as the
reagent gas and typical source conditions were the same as
EI. Probe spectra were obtained using both EI mode and CI
conditions. Samples were analysed with a direct inlet probe.
The software used on the Thermo Electron instrument for
data processing is Mass Lab Version