Fast drug stability determination by LC variable-parameter kinetic experiments.

Variable-parameter kinetic experiments were carried out using HPLC as analytical instrument. The hydrolysis of aspirin was followed both at variable-temperature and at variable-pH conditions. The peak areas relative to salicylic acid were processed by direct fit to a mathematical model and/or by differential method obtaining, by single experiments, the values of the apparent rate constant in the whole range of temperature and pH studied.

Variable-ionic strength kinetic experiments in drug stability studies.

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.

Temperature-rate profiles by polarimetric variable-temperature kinetic experiments to study racemization reactions.

The racemization of (-)-adrenaline was followed by polarimetric variable-temperature kinetic experiments obtaining activation parameters and k(obs)(T) profile in one tenth of the time usually spent for traditional kinetic runs. A polarimeter connected to a computer for the acquisition and processing of the analytical data was used. The kinetic profiles were processed by both an integral method and a differential method.