Another approach is to fit the experimental VLE data (CO 2 partial pressure and speciation data) to the parameters of a thermodynamic model for the chemical potentials to obtain the equilibrium constant. As a result of the different approximation approaches, the spread of the literature values is partly due to differences in the activity coefficient models used by the authors, and more likely due to the difficulty in the experimental NMR measurement of the concentrations of the bicarbonate ion and neutral amine species, which is difficult to distinguish from the protonated and carbonate ion in the NMR peaks. The experimental carbamate formation constant data are limited and likely subject to significant uncertainty. For example, carbamate formation constants of MEA have been measured using various experimental methodology including NaOH titration of the carbamate solution, fitting thermodynamic models to vapour-liquid-equilibrium (VLE) data of CO 2 -loaded solutions, and to CO 2 partial pressure data, NMR titrations, 10 calorimetric studies and H-NMR Spectroscopy, 4 giving values ranging from 1.31 5 -1.85. We compare our predicted values with the scarcely available experimental data in Table . Given the lack of the pK c data from different measurement, based on the MEA data, we infer the uncertainty in the experimental to be ≈ 0.25 pK unit comparable to that of the simulation data. Lack of comprehensive and accurate experimental pK c data complicates fair comparison with the simulations data. Overall, our predictions are in reasonable agreement with the available experimental data.