Determination and correlation of the partition coefficients of 48 volatile organic and environmentally relevant compounds between air and silicone oil

Abstract

Many emerging bioprocesses include a second, non-aqueous phase liquid in which the key substrate or product partitions for either enhanced interphase mass transfer, concentration dampening, or in-situ product extraction. Knowledge of the partition coefficient between air and the non-aqueous is relevant for process optimization and modeling. In here, experiments were conducted to determine the air-silicon oil partition coefficients (P) of 48 environmentally relevant compounds including many volatile organic compounds, chlorinated solvents, and aromatics compounds. A mass balance method gave reliable results, whereas the EPICS method did not. The value of the ratio of Henry’s constant (H) divided by P which is the partition coefficient between silicone oil and water served as a parameter to distinguish which compound would most benefit from including silicon oil as a non-aqueous phase. P values decreased slightly with decreasing viscosity of silicon oil between 50 and 5cSt, and a simple relationship was proposed to calculate P at 5 or 50cSt based on values at 20cSt. Lastly, a quantitative structure activity relationship (QSAR) model using the Wiener index as a single parameter could successfully fit P values within specific chemical groups. Overall, the mini-database of P values and models developed in this study provide new tools for the optimization and modeling of processes that include silicon oil as a second liquid phase.