Mass transport in (drug + cyclodextrin) solutions is investigated by using Taylor dispersion technique, monitored by differential refractometry, to measure ternary mutual diffusion in aqueous solutions of {L-dopa + (NaSO3)n-beta-CD} (the sodium salt of sulfated beta-cyclodextrin). The values of the binary mutual diffusion coefficients of both aqueous L-dopa and aqueous (NaSO3)(n)-beta-CD solutions are close to each other differing only by a few per cent units. As a result, the eigenvalues for the matrix of the ternary D th diffusion coefficients for aqueous {L-dopa(1) + (NaSO3)(n)-beta-CD(2)} solutions are nearly identical, and the numerical analysis of the Taylor dispersion data may be ill-conditioned in view of the unreliable data obtained from their analysis. To overcome these difficulties, the pseudo-binary diffusion approximation is used to evaluate in a simple way this ternary system. The pseudo-binary diffusion coefficient values found, D-p1 and D-p2, are very close to the binary diffusion ones, being the cross-coefficients approached zero, within the experimental error. From the obtained results, and under the circumstances of this study, we may deduct that no interaction between L-dopa and NaSO3 beta CD was determined. (C) 2018 Elsevier Ltd.