Reactive extraction and recovery of mono-caffeoylquinic acids from tobacco wastes by trialkylphosphine oxide

Abstract The feasibility of reactive extraction of mono-caffeoylquinic acids (mono-CQAs) from aqueous extract solutions of tobacco wastes was studied. The mixed solvent system, initial pH, extractant concentration, complexation stoichiometry, equilibrium and mechanism were discussed. The results indicated that the extraction ability of extractants decreases in the order trialkylphosphine oxide (TRPO)> N 235≈tributylphosphate (TBP)>trioctyl phosphate (TOP). Using a 1:1 ratio of 20% TRPO/kerosene to sample volume, one step recovered 94.9% of the mono-CQAs from an aqueous solution at pH 3. The complexation stoichiometry between TRPO and the mono-CQAs was 1:2 or 1:3, but the formation of 1:2 complexes was favored. The extraction equilibrium of the mono-CQAs was fit to a Henry isotherm, and the process was exothermic. Hydrogen-bond interactions between TRPO and mono-CQAs were confirmed by Fourier-transform infrared (FTIR) spectra, and the changes in the wavenumbers of absorbances increased with decreasing p K a values of the mono-CQAs.