Qualification of EYTEX data: a user's guide

By Martin, C.G.

The EYTEX system has been shown to be a very useful tool in the in vitro testing of toiletry raw materials. However, the interpretation of the results is not always simple. It requires an understanding of the physicochemical characteristics of the samples and of their interactions with components of the EYTEX system. The results of 364 assays using the EYTEX standard assay, membrane partition assay, rapid membrane assay and upright membrane assay protocols have been collated against the problem areas for each method. These assays were performed on a collection of 18 pure surfactant raw materials and also on blends of surfactants. The results for 18 surfactants are reviewed according to surfactant type and interpreted with reference to the concentration-response curve for each material. This paper describes the problem areas of inhibition, interference and negative optical densities associated with the non-qualification of EYTEX assays, and shows how they have been overcome. In conclusion, some guidelines for using a concentration-response assay are given, so that the optimum concentration for a dose-response assay for a new sample can be obtained with the minimum waste of time or reagents.