A contribution to the derivative ratio spectrum method

The performance of two graphical methods (the derivative ratio spectrum method and its variant with normalised divisor) for the determination of the resolution of several binary mixtures of analytes is compared. This paper demonstrates that normalized spectra used as divisors facilitate optimization of the working conditions and diminishes quantitation errors. The additional use of diode array spectrophotometers allows 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-perphenazine, were assayed. The results obtained by using the proposed method in its conventional and modified variants are discussed. On the other hand, a multi-wavelength regression method is suggested for the determination of several metal ions by using an organic reagent as chelating agent. It was shown that it is possible to determine the analytes without any previous knowledge of stoichiometry of the complexes involved and how the contribution from excess of chelating agent can be eliminate. The method has been validated on several binary mixtures of Fe(III), Cu(II) and Zn(II) by using 4-(1′H-1′,2′,4′-trizolyl-3′-azo)-2-methylresorcinol (TrAMeR) as chelating agent.