A method for analysing a mixture M comprising: (i) a first species which is monodisperse, and (ii) a second species which is polydisperse and which has a response coefficient which is distinct from the response coefficient of the first species (i) on at least one detection device, said method comprising the following steps: the mixture M is injected at the inlet of a capillary tube and forced to be transported in said tube by the flow of a carrier liquid induced by a positive hydrodynamic and/or hydrostatic pressure between the inlet and the outlet of the capillary tube, whereby a phenomenon of Taylor dispersion of the species of the mixture M occurs in the tube; by using a detector able to detect simultaneously both species (i) and (ii) and placed in the region of the outlet of the capillary tube, a signal reflecting the Taylor dispersion obtained in step is measured; the signal obtained in step is analysed by using an analysis device, so as to determine specific contributions of species (i) and (ii) and thereby establishing at least one of the followings: - the content of species (i) and/or (ii) in the mixture M; and/or - the mean hydrodynamic radius of the species (ii) or the hydrodynamic radius of species (i), wherein the species (i) an (ii) have two distinct hydrodynamic radii, and species (i) is a species of a predetermined nature and wherein, in step, the respective contributions of species (i) and (ii) in the signal obtained in step are established, whereby the elution profiles of species (i) and (ii) are obtained, which allows to determine the content of species (i) and/or (ii) in the mixture M, and/or the mean hydrodynamic radius of the species (i) and/or (ii), whereby the mixture M is injected so as to make a unit step injection, and the respective contributions of species (i) and (ii) in the signal T n ( t) obtained in step are established, in step, by fitting onto the signal T n ( t) the following fit function: C n t = C 0 i 2 1 − erf t − t d, n σ i, n 2 + C 0 ii 2 1 − erf t − t d, n σ ii, n 2, resulting in the determination of the following parameters: t d,n is the time when an inflexion point is detected in the edge of the signal; σ i,n and σ ii,n, the variances for the contribution of the two species (i) and (ii); and, C 0 i and C 0 ii, the maximal absorbance of the two species (i) and (ii). (i) a first species which is monodisperse, and (ii) a second species which is polydisperse and which has a response coefficient which is distinct from the response coefficient of the first species (i) on at least one detection device, the mixture M is injected at the inlet of a capillary tube and forced to be transported in said tube by the flow of a carrier liquid induced by a positive hydrodynamic and/or hydrostatic pressure between the inlet and the outlet of the capillary tube, whereby a phenomenon of Taylor dispersion of the species of the mixture M occurs in the tube; by using a detector able to detect simultaneously both species (i) and (ii) and placed in the region of the outlet of the capillary tube, a signal reflecting the Taylor dispersion obtained in step is measured; the signal obtained in step is analysed by using an analysis device, so as to determine specific contributions of species (i) and (ii) and thereby establishing at least one of the followings: - the content of species (i) and/or (ii) in the mixture M; and/or - the mean hydrodynamic radius of the species (ii) or the hydrodynamic radius of species (i), - the content of species (i) and/or (ii) in the mixture M; and/or - the mean hydrodynamic radius of the species (ii) or the hydrodynamic radius of species (i),