Fig. 4. Physico-chemical data-integrative grouping of petroleum substances. Mass % evaporation data (in 50 °C increments) for Concawe samples from four product groups (SRGO, OGO, VHGO, and RAE) were integrated in ToxPi to yield evaporation profiles, as well as a chemical ranking according to their overall volatility, i.e. mass % evaporation data derived ToxPi score (a). Potential correlations in the originating data set were analyzed using the hclust function in r (b). Physico-chemical data derived ToxPi scores were subsequently correlated with bioactivity data-derived ToxPi scores (c). [VHGO = vacuum & hydrotreated gas oils; SRGO = straight run gas oils; OGO = other gas oils; RAE = residual aromatic extracts].