Method for determining the size distribution of a mixture of molecule or particle species including the following steps: - injecting a sample of the mixture to be analysed inside a capillary in which an eluent is flowing; - transporting the sample injected along the capillary from an injection section to a detection section thereof, in experimental conditions suitable to generate a Taylor dispersion phenomenon that is measurable at the level of the detection section; - generating, by means of a suitable sensor included in the detection section, a signal characteristic of the Taylor dispersion of the transported sample; - processing the detection signal in order to obtain an experimental Taylor signal Ŝ ( t); and - analysing the experimental Taylor signal Ŝ ( t), characterised in that the step of analysing an experimental Taylor signal Ŝ ( t) of a sample of the mixture consists of searching an amplitude distribution P ( G ( c)) that allows the experimental Taylor signal Ŝ ( t) to be broken down into a sum of Gaussian functions by means of the equation: S ^ t ≡ ∫ 0 ∞ P G c G c c / 2 exp − t − t 0 2 G c c d G c where - t is a variable upon which the experimental Taylor signal depends and t 0 is a value of the variable t common to the various Gaussian functions and corresponding to the peak of the experimental Taylor signal Ŝ ( t); - G ( c) is a characteristic parameter of a Gaussian amplitude function P ( G ( c)) and is associated: - where c = 1, with the diffusion coefficient D of a species according to the relation G 1 = 12 D / R c 2 t 0 - for c = -1, to the hydrodynamic radius R h of a species according to the relation G − 1 = 2 k B T πη R c 2 t 0 R h − 1; and - for c= -1/ d f = -(1+a)/3, to the molar mass M of a species according to the relation G = 2 k B T πη R c 2 t 0 10 π N a 3 K 1 / 3 M − 1 + a 3, Where d f =3/(1+a) is the fractal dimension of the object and k B is the Boltzmann constant, T is the absolute temperature expressed in Kelvin at which the experiment is conducted, η is the viscosity of the eluent used, R c is the internal radius of the capillary used, N a is Avogadro's number, and K and a are Mark Houwink coefficients, by implementing a constrained regularisation algorithm consisting of minimising a cost function H α including at least one constraint term associated with a constraint that must observe the amplitude distribution P ( G (c)) that is the solution of the foregoing equation, whereby the minimisation is carried out on an interval of interest of the values of the parameter G (c). - injecting a sample of the mixture to be analysed inside a capillary in which an eluent is flowing; - transporting the sample injected along the capillary from an injection section to a detection section thereof, in experimental conditions suitable to generate a Taylor dispersion phenomenon that is measurable at the level of the detection section; - generating, by means of a suitable sensor included in the detection section, a signal characteristic of the Taylor dispersion of the transported sample; - processing the detection signal in order to obtain an experimental Taylor signal Ŝ ( t); and - analysing the experimental Taylor signal Ŝ ( t), - t is a variable upon which the experimental Taylor signal depends and t 0 is a value of the variable t common to the various Gaussian functions and corresponding to the peak of the experimental Taylor signal Ŝ ( t); - G ( c) is a characteristic parameter of a Gaussian amplitude function P ( G ( c)) and is associated: - where c = 1, with the diffusion coefficient D of a species according to the relation G 1 = 12 D / R c 2 t 0 - for c = -1, to the hydrodynamic radius R h of a species according to the relation G − 1 = 2 k B T πη R c 2 t 0 R h − 1; and - for c= -1/ d f = -(1+a)/3, to the molar mass M of a species according to the relation G = 2 k B T πη R c 2 t 0 10 π N a 3 K 1 / 3 M − 1 + a 3, Where d f =3/(1+a) is the fractal dimension of the object and k B is the Boltzmann constant, T is the absolute temperature expressed in Kelvin at which the experiment is conducted, η is the viscosity of the eluent used, R c is the internal radius of the capillary used, N a is Avogadro's number, and K and a are Mark Houwink coefficients, by implementing a constrained regularisation algorithm consisting of minimising a cost function H α including at least one constraint term associated with a constraint that must observe the amplitude distribution P ( G (c)) that is the solution of the foregoing equation, whereby the minimisation is carried out on an interval of interest of the values of the parameter G (c). - where c = 1, with the diffusion coefficient D of a species according to the relation G 1 = 12 D / R c 2 t 0 - for c = -1, to the hydrodynamic radius R h of a species according to the relation G − 1 = 2 k B T πη R c 2 t 0 R h − 1; and - for c= -1/ d f = -(1+a)/3, to the molar mass M of a species according to the relation G = 2 k B T πη R c 2 t 0 10 π N a 3 K 1 / 3 M − 1 + a 3,