Table 2. Compounds classes and their relative contribution to perform MFA dimensions.

Compound classa	Dimension 1	Dimension 2
Other compounds	18.12	17.89
Hydrocarbons	17.99	16.42
Aromatic hydrocarbons	17.75	6.14
Sulphur compounds	17.65	21.46
Terpene compounds	14.27	18.29
Phenol compounds	14.22	19.80

Each dimension of a multivariate analysis can be described by the variables which participate to the construction of the factorial axes.

^aCompound classes are sorted according to their relative contribution of dimension 1.