Universal predictive models on octanol‐air partition coefficients at different temperatures for persistent organic pollutants

Abstract

Owing to the importance of octanol-air partition coefficients (KOA) in describing the partition of organic pollutants from air to environmental organic phases, the paucity of KOA data at different environmental temperatures, and the difficulty or high expenditures involved in experimental determination, the development of predictive models for KOA is necessary. Approaches such as this are greatly needed to evaluate the environmental fate of the ever-increasing list of production chemicals. Partial least squares (PLS) regression with 18 molecular structural descriptors was used to develop predictive models based on directly measured KOA values of selected chlorobenzenes, polychlorinated biphenyls (PCBs), polychlorinated naphthalenes, polychlorinated dibenzo-p-dioxins/dibenzofurans, polybrominated diphenyl ethers, polycyclic aromatic hydrocarbons, and organochlorine pesticides (OPs). An optimization procedure resulted in two temperature-dependent universal predictive models that explained at least 91 % of the variance of log KOA. Model 1 was the more general of the two models that could be used for all the persistent organic pollutant (POP) classes investigated. Although model 1 performed poorly for select OPs, this was attributed to wide variability in structural types within this subset of POPs and their diversity compared to the other POP classes that were investigated. The exclusion of the structurally complex OP subset resulted in a more precise model, model 5. Intermolecular dispersive interactions (induced dipole-induced dipole forces) between octanol and solute molecules play a decisive role in governing KOA and its temperature dependence. Further investigations are needed to better characterize the steric structures of the POPs under study, especially of OPs.

Docking and 3D-QSAR studies on the Ah receptor binding affinities of polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs)

“…Simca-S adopts leave-many-out cross validation to determine the number of PLS components (A). Cross-validation simulates how well a model predicts new data, and gives a statistical Q 2 CUM (the fraction of the total variation of the dependent variables that can be predicted by all the extracted components) for the final model (Chen et al, 2004). When Q 2 CUM of a model is larger than 0.5, the model is believed to have a good predictive ability (Golbraikh and Tropsha, 2002).…”

“…When Q 2 CUM of a model is larger than 0.5, the model is believed to have a good predictive ability (Golbraikh and Tropsha, 2002). The PLS analysis was performed repeatedly so as to eliminate redundant molecular structural parameters, as done in the previous studies (Chen et al, 2004;Li et al, 2010a). The model predictability was evaluated by external validation.…”

QSAR studies on the depuration rates of polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers and polychlorinated biphenyls in mussels (Elliptio complanata)

“…Cross-validation simulates how well a model predicts new data, and gives a statistical Q 2 CUM (the fraction of the total variation of the dependent variables that can be predicted by all the extracted components) for the final model. The PLS analysis was performed repeatedly so as to eliminate redundant molecular structural parameters, as done in previous studies [35].…”

Development and assessment of quantitative structure-activity relationship models for bioconcentration factors of organic pollutants

“…Thus, a total of 16 theoretical molecular structural descriptors were selected to describe these interactions. Some descriptors related to molecular volume, such as molecular weight (M W ), average molecular polarizability (α), total energy (TE), standard heat of formation (∆H f ), Connolly accessible area (CAA), Connolly molecular area (CMA), Connolly solvent-excluded volume (CSEV) and ovality (Ov) [31] . They were selected to characterize the cavity forming interactions.…”