Method for quantitative analysis of an elemental composition of material from a sample having several elements able to generate plasma and emit radiation, each element containing several constituents, the method comprising: • a step of heating the material of sample so as to generate plasma emitting radiation, • a step of identifying the spectral lines of interest among spectral lines emitted by the constituents of each heated element of sample, • a step of measuring the intensities of the spectral lines of interest, • a step of estimating a temperature of plasma, • a step of estimating an electron density (n e) of plasma, • a step of estimating a width of plasma in a direction of observation, • a step of calculating a chemical composition of plasma from the values of the temperature, the electron density (n e) and the relative values of the elemental concentrations of each element of sample, • a step of calculating an absorption coefficient of plasma at the spectral lines of interest, characterized in that it also includes: • a step of calculating a spectral radiance of plasma, • a step of calculating a spectrum from the calculated chemical composition of plasma, the calculated absorption coefficient of plasma and the calculated spectral radiance of plasma, a step of comparing the intensity and the shape of the calculated spectrum with the intensity and shape of the measured spectrum, in that the steps of calculating the chemical composition, of calculating the absorption coefficient, of calculating the spectral radiance, of calculating the spectrum and of comparing are repeated iteratively, the values of temperature of plasma, electron density (n e) of plasma, width of plasma and the elemental concentrations being adjusted at each iteration, until obtaining a difference between the intensity and shape of the calculated spectrum and the intensity and shape of the measured spectrum which is less than or equal, by absolute value, to a predetermined threshold value, and in that it also comprises a step of dividing plasma into an increasing number of zones,,, in the direction of observation, each characterized by different values of temperature and electron density, said dividing step depending on obtaining a minimum of the difference between the intensity and shape of the calculated spectrum and the intensity and shape of the measured spectrum, said minimum being greater, by absolute value, than the predetermined threshold value. • a step of heating the material of sample so as to generate plasma emitting radiation, • a step of identifying the spectral lines of interest among spectral lines emitted by the constituents of each heated element of sample, • a step of measuring the intensities of the spectral lines of interest, • a step of estimating a temperature of plasma, • a step of estimating an electron density (n e) of plasma, • a step of estimating a width of plasma in a direction of observation, • a step of calculating a chemical composition of plasma from the values of the temperature, the electron density (n e) and the relative values of the elemental concentrations of each element of sample, • a step of calculating an absorption coefficient of plasma at the spectral lines of interest, • a step of calculating a spectral radiance of plasma, • a step of calculating a spectrum from the calculated chemical composition of plasma, the calculated absorption coefficient of plasma and the calculated spectral radiance of plasma,