Statistical analysis was undertaken using multivariate techni-
ques common to electronic noses. First, features were extracted
from the raw data based on the baseline-corrected voltage chan-
ges averaged over 3 points (Sig-Base3), the response integrals from
the start of response to the maximum response (AreaMax) and the
times for the sensor responses to return from maximum to 50% of
that value (T50). Eqs. (1)–(3) were used to calculate these three
features in respective order: