Partitioning of hydrogen peroxide between the gas and liquid phases in the presence of surfactant

Gas-liquid phase partitioning is a key physical property that can predict the environmental fate of a compound between two phases. Several environmental factors have been known to affect the gas-liquid phase partitioning. We investigated the influence of surfactant on the gas-liquid phase partitioning of hydrogen peroxide (H2O2). The surfactant used was ammonium perfluorooctanoate (APFO). H2O2 solution containing the surfactant was equilibrated in a closed system and gas phase H2O2 concentration was measured by the peroxyoxalate chemiluminescence (PO-CL) method. Gas phase H2O2 concentrations remained constant below the critical micelle concentration (CMC) and increased linearly with surfactant concentration above the CMC, which indicated that surfactant micelles influenced the gas-liquid phase partitioning of H2O2. This result showed that H2O2-micelle interactions are less favorable than H2O2-H2O interactions. Surfactant monomers did not affect the gas-liquid phase partitioning of H2O2 due to the absence of micelles. Solvent (methanol) effect was also investigated and showed that gas phase H2O2 concentrations increased with the addition of solvent. This indicated the unfavorable interaction of H2O2 with hydrophobic medium compared to hydrophilic one. It is consistent with the result that H2O2-micelles has a weaker interaction than H2O2-water because surfactant micelles are hydrocarbon-like organic phase rather than aqueous phase.