DETERMINATION OF INITIAL CONCENTRATION OF AN ANALYTE BY KINETIC DETECTION OF THE INTERMEDIATE PRODUCT IN CONSECUTIVE FIRST-ORDER REACTIONS USING AN EXTENDED KALMAN FILTER

Many analytical reagents react with analytes according to a rate law described by a consecutive first-order reaction mechanism, A-->B-k1 -->C-k2, where a product formation step is followed by a product degradation step. In many cases, consecutive first-order reactions are used to determine the initial concentration of analyte A by kinetic detection of the intermediate product B. In this work, the factors that affect the determination of the initial concentration of analyte-and the kinetic parameters for this class of reactions have been investigated by computer simulations using an extended Kalman filter. The flip-flop phenomenon exhibited by this kinetic model is discussed, and a unique approach for the determination of the initial concentration of analyte is proposed. Empirical and residual methods for obtaining initial estimates for the rate constants and the initial concentration from the kinetic data, based on the model for consecutive first-order reactions, have been developed. The effects of changing the rate constants, the initial concentration of analyte, the mismatch between the measured time and the real time, the data density, the fitting range, and the initial estimate for the background signal have been evaluated by using synthetic data with Gaussian-distributed mise. The percent errors in the estimated values for the parameters that are proportional to the initial concentration of analyte have been evaluated for each of the different variables under consideration. Plots of these errors as a function of the various effects mentioned above permit the methods to be completely characterized.