Abstract
Mixtures containing ether sulfate based surfactants (SLEnS) and linear alkylbenzene sulfonic acid (LAS) are relatively common in personal care and household products. When in mixture, they form mixed micelles, which act as reservoirs for the cleaning process. The increase of ethylene oxide (EO) units in the head of SLEnS lowers the critical micelle concentration, meaning that less quantity of each surfactant is needed to form the micelles. Within an eco-friendly perspective this is advantageous since less chemicals are expected to be released into the environment. But, this advantage will only be effective if variations with the higher number of EO units exhibit a lower toxicity as well. Despite its wide use in commercial products, the ecotoxicity of these micelles and the influence of the EO units on their toxicity still did not receive the necessary attention. In this context, the present study aimed at assessing the influence of the number of ethylene oxide (EO) units in the head groups of SLEnS on the toxicity of the SLEnS-LAS mixed micelles to the bacterium Vibrio fischeri (Microtox (R) assay, here used as a fast and preliminary ecotoxicological indicator). The SLEnS variants with fewer EO units showed higher toxicity relatively to those with more EO units - EC50 range (0-50 EO units): 0.56-8.59 mg L-1, thus they can be suggested as environmentally safer variants to be used in personal care and household products. Provided the consistency of Microtox (R) results as obtained here, this quick and cost-effective procedure can be an important tool towards the development of eco-friendlier surfactant-based formulations. (C) 2018 Elsevier B.V. All rights reserved.