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

Ternary mutual diffusion coefficients (D-11, D-22, D-12 and D-21) measured by the Taylor dispersion method are reported for aqueous solutions of paracetamol (1) in the presence of beta-cyclodextrin (beta-CD) (2) at 298.15 K and solute concentrations up to 0.050 (mol dm(-3)). The diffusion of paracetamol and beta-CD is coupled, as indicated by non-zero values of the cross-diffusion coefficients, D-12 and D-21 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):(beta-CD) complex. The association constant K= 27 (mol(-1) dm(3)) for the formation of the complex was estimated from the diffusion data. (C) 2021 Elsevier Ltd.

Automated summary

Ternary mutual diffusion coefficients were measured for aqueous solutions of paracetamol in the presence of beta-cyclodextrin at 298.15 K, showing coupled diffusion and interactions between the drug and carbohydrate. The measured diffusion coefficients closely matched the predicted values from a model assuming a 1:1 complex, with an association constant of 27 mole per cubic decimeter estimated from the data.