Host-guest paracetamol/cyclodextrin complex formation evaluated from coupled diffusion measurements

Abstract

Ternary mutual diffusion coefficients (D11, D22, D12 and D21) measured by the Taylor dispersion method are reported for aqueous solutions of paracetamol (1) in the presence of β-cyclodextrin (β-CD) (2) at 298.15 K and solute concentrations up to 0.050 (mol dm−3). The diffusion of paracetamol and β-CD is coupled, as indicated by non-zero values of the cross-diffusion coefficients, D12 and D21 measuring interactions between the fluxes of the drug and the carbohydrate. The measured ternary diffusion coefficients are in close agreement with the diffusion coefficients predicted by a model assuming a 1:1 (paracetamol):(β-CD) complex. The association constant K = 27 (mol−1 dm3) for the formation of the complex was estimated from the diffusion data.