A limitation of the Microtox® test for toxicity measurements of nonionic surfactants

Kim B. Sherrard, Philip J. Marriott, Malcolm J. McCormick, Keith Millington

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The Microtox® test was successfully used to measure EC50 values of nonionic polyethoxylate surfactants. However, toxicity measurements of real samples that contain surfactants above a particular concentration, termed the critical toxicity concentration (CTC) are not valid. These samples require dilution before the test is performed, and because the relationship between toxicity and concentration is not linear above the CTC, the EC50 cannot be extrapolated hack to give the toxicity of the original concentrated sample and a true estimation of toxicity is therefore not possible. This phenomenon may be related to the minimum surface tension requirement of the bacteria or other physical properties of the surfactant such as the tendency to assemble at interfaces and surfaces and the tendency to form micelles.

Original languageEnglish
Pages (from-to)1034-1037
Number of pages4
JournalEnvironmental Toxicology and Chemistry
Issue number7
Publication statusPublished - 1 Jan 1996
Externally publishedYes


  • Critical micelle concentration
  • Microtox
  • Surface tension
  • Toxicity

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