In this work, a review of different methods used for the simultaneous determination of several components through spectrophotometric and fluorimetric measurements is carried out including derivative methods. Several methods are described, like multilinear regression analysis and partial least squares, as well as some other for non-linear systems, like the Gauss-Newton, simplex and neural network methods. The effect of the contribution of unknown species has been considered. A novel approach related with the simultaneous determination of a catalyst and an activator or inhibitor has been included. Several manual and automated methods using flow techniques are described, including the resolution of overlapped HPLC peaks. Resolution of compound mixtures with highly overlapped spectra • Different methods for the simultaneous determination of several components are considered • Spectrophotometric and fluorimetric measurements, as well as their derivative methods are taken into account. • Multilinear regression analysis and partial least squares are described • Also some other for non-linear systems like the Gauss-Newton, simplex and neural network methods are described • A novel approach for the simultaneous determination of a catalyst and an activator has been included