Variable‐ionic strength kinetic experiments in drug stability studies

ABSTRACT: The dependence of the pseudo-first-order rate constant on the ionic strength for the alkaline hydrolysis of indomethacin has been obtained, for the first time, in a single kinetic experiment carried out by varying with time the salt concentration inside the reaction vessel. The kinetic profile obtained was processed using as a mathematical model the variable-parameter kinetic equation containing the Bronsted–Bjerrum equation as the dependence function. The results are in good agreement with those obtained by the traditional method but the experimental time is reduced to about one-tenth. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association