Quality Assurance is a wide ranging concept covering all matters that individually or collectively influence the quality of product.Ultraviolet Spectroscopy is an absorption spectroscopy in which the excitation of electrons is accompanied by changes in the vibrational and rotational quantum numbers.Simultaneous equation method is having special advantages over other methods because of its simplicity and rapidity in performing. Simultaneous equation is based on simple principle, that the absorbance of mixture at particular wavelength is additive of absorbances of individual component in sample mixture at that wavelength. Это и многое другое вы найдете в книге RP-HPLC Method: A Simultaneous Estimation (Prachi Pawar,Vidhyadhar Bankar and Preeti Gaikwad)