QSAR modelling of the toxicity of some technical non-ionic surfactants towards fairy shrimps

The toxicity of a number of non-ionic surfactants towards Thamnocephalus platyurus (sweet water fairy shrimp) has been examined. The measurements have been performed with the use of so-called Toxkits, and the results have been expressed both as a mean LC(50) value for each of the surfactants, and with a relative scale estimated using of multi dimensional scaling (MDS). An algorithm is shown in matlab code, with which it is possible to per form MDS on a difference matrix with a lot of systematically missing values. The thus obtained results have been combined with the physico-chemical data for the surfactants, and QSAR models have been estimated for the toxicity (log(LC(50))) of the surfactants. The physico-chemical properties with the main influence on the models were the hydrophilic-lipophilic-balance (HLB), the hydrophobicity (log P), the critical micellar concentration (CMC) and the number of carbon atoms in the hydrophobic part (C) of the surfactant.