Kinetic Spectrum Method for Analysis of Simultaneous, First-Order Reactions and Application to Copper(II) Dissociation from Aquatic Macromolecules

A nonlinear differential rate method that requires no prior knowledge of rate constants, Initial concentrations, or number of components Is developed to analyze multicomponent, first-order or pseudo-first-order reactions. The method gives a kinetic spectrum with peak maxima corresponding to rate constants and peak areas equal to initial concentrations of components. Complete resolution of two components requires a rate constant ratio greater than about 40. The method was applied to a study of Cu(II) dissociation from estuarine humic material In which a Cu(II)-humic mixture was reacted with a colorimetric reagent and absorbance followed from 50 ms to 1835 s. The kinetic spectrum showed bound Cu(II) distributed In two regions over a wide range of rate constants. About 43% of the total Cu(II) dissociated in times greater than 50 ms corresponding to rate constants ≤40 s⁻¹.