Computer‐controlled system designed to measure photodegradation of photochromic compounds

In this paper, we describe a new, entirely computer‐controlled apparatus designed for degradation studies of photochromic compounds. Photodegradation can be performed in three different ways using, in addition to the usual flash mode, the cyclic and continuous modes which more closely simulate daylight exposure conditions. In each mode, the ‘‘fatigue resistance’’ parameter is computed. Moreover, the spectrokinetic parameters of photomerocyanine species can be obtained from the kinetic mode. Due particularly to the fully computer‐controlled experimental setup, the between‐day reproducibility of the initial absorbance and fatigue resistance determinations are better than 4% and 6%, respectively. Owing to the modular design of the menu‐driven software, written in C language, the apparatus is very flexible and easy to use.