Adsorption and solidification of peppermint oil on microcrystalline cellulose surface: An experimental and DFT study

Microcrystalline cellulose, a well-known pharmaceutical excipient can adsorb and solidify peppermint oil i.e., a multi-component liquid model drug. The nature of intermolecular forces governing the process was a question. Peppermint oil adsorption kinetics on the microcrystalline cellulose surface was studied in liquid phase as a function of the adsorbate concentration. Peppermint oil components were separated and analyzed using gas chromatography-mass spectroscopy technique. Peppermint oil adsorption kinetics was best fitted to a pseudo-first order kinetic model showing equilibrium adsorption after 12 h. Adsorption of the constituent species was not occurred selectively considering the numerical values of the affinity constant (k(1)). A linear correlation was observed between the extent of the constituent species adsorption and their relative concentration in the mixture. The adsorption results were best described by Langmuir and Freundlich isotherms elucidating 110 mg.g(-1) maximum peppermint oil adsorption and solidification capacity on microcrystalline cellulose surface. The significance of dispersive intermolecular interactions was concluded by analyzing Hansen solubility parameter for the pairs of adsorbent-adsorbate species. In silico molecular simulation of the interactions showed a linear correlation between binding energies and k(1) values with a close-matching for all peppermint oil constituent species. (C) 2019 Elsevier B.V. All rights reserved.