Abstract

A collection of data on the Draize rabbit eye test has been analysed using a set of physicochemical descriptors that we have previously put forward. These descriptors are compound parameters as follows: R2 is an excess molar refraction, p2 H is the polarizability/dipolarity, ∑aH 2 and ∑b2 H are the effective hydrogen bond acidity and basicity, and logL16 is a descriptor where L16 is the vapour-hexadecane solubility at 25°C. When applied to Draize eye scores for 38 pure bulk liquids, a very poor equation was obtained. However, when the DES values were correlated as log, where Po is the liquid vapour pressure, an excellent equation was found. On transforming the calculated log values back to calculated DES values, there was good agreement with the original DES values. It is suggested that the DES/Po values refer to transfer of the irritant from the vapour phase to the biophase, and that the success of the present treatment demonstrates that for the pure liquids studied, a major factor in the Draize eye test is simply the transfer of the liquid to the biological system.