Characteristics of methods for the simultaneous determination of catalysts by first-order inhibition kinetics.

Abstract

Factors that affect the simultaneous kinetic determination of catalysts based on differences in rates of inhibition by a common inhibitor are investigated by computer simulation. Both derivative and integral models for the kinetic responses are studied. Nonlinear regression is used to fit data with a fixed level of noise for the combined responses due to the first-order inhibition of two catalysts. Effects of rate constants, ratios of rate constants, fitting ranges, data density, and number of replicate determinations on reliability, useful activity range, sensitivity, scatter, limits of detection, and measurement/data-processing times are considered. It is found that values for rate constants, ratios of rate constants, and fitting ranges which provide results with desired reliability are restricted. Small ratios of rate constants and short fitting ranges were observed to produce the largest useful activity ranges and shortest measurement times but also gave the worst accuracy and most dependence on initial estimates of fitting parameters. Values of the coefficients of correlation between the individual first-order responses can aid in the selection of the smallest ratio of rate constants and fitting range which will yield suitable results.