A CONTRIBUTION TO THE DERIVATIVE RATIO SPECTRUM METHOD

The performance of two graphical methods (the derivative ratio spectru m method and its variant with normalized divisor) for the determinatio n of the resolution of several binary mixtures of analytes is compared . This paper demonstrates that normalized spectra used as divisors fac ilitate optimization of the working conditions and diminishes quantita tion errors. The additional use of diode array spectrophotometers allo ws quantitation of second order derivative ratio spectra. In order to validate the proposed approach to derivative ratio spectra, two binary mixtures, acetylsalicylic acid-salicylamide and imipramine-perphenazi ne, were assayed. The results obtained by using the proposed method in its conventional and modified variants are discussed. On the other ha nd, a multi-wavelength regression method is suggested for the determin ation of several metal ions by using an organic reagent as chelating a gent. It was shown that it is possible to determine the analytes witho ut any previous knowledge of stoichiometry of the complexes involved a nd how the contribution from excess of chelating agent can be eliminat e. The method has been validated on several binary mixtures of Fe(III) , Cu(II) and Zn(II) by using -(1'H-1',2',4'-trizolyl-3'-azo)-2-methylr esorcinol (TrAMeR) as chelating agent.