title: Application of ring study: water toxicity determinations by bioluminescence assay with Vibrio fischeri.
abstract: Acceptance of toxicity bioassays as effective analytical tools in environmental areas needs guarantees of standardization but also validation. Ten European laboratories took part in an inter-laboratory study using different commercial devices based on bioluminescence inhibition of bacteria Vibrio fischeri. Reproducibility and stability by short toxicity endpoints, effective concentration that gives 10%, 50% and 80% of inhibition (EC(10), EC(50) and EC(80)) is evaluated. Parametric and non-parametric statistic is applied and performance of participant laboratories is addressed by z-scores calculated by non-parametric statistic. z-Score classification was based on harmonised protocol for proficiency testing of analytical laboratories (satisfactory |z|< or =2; questionable 2<|z|< or =3; unsatisfactory |z|>3). Tested samples were phenol, 3,5-dichlorophenol and influent wastewater. Based on z-score classification, more than 70% of the laboratories showed a satisfactory performance for phenol, 3,5-dichlorophenol and influent wastewater (86%, 90% and 70%, respectively). Reproducibility and stability was observed in toxicant references and in wastewater samples. EC(80) determination appears to be more robust that EC(10) and EC(50). EC determinations can be considered favorable at 5 and 15 min of exposition, in particular for EC(80). The use of different commercial devices can not be considered an additional source of variation.
authors.affiliation: Department of Analytical Chemistry, University of Almería, Almería, Spain. dhernan@ual.es
authors.forename: M D
authors.initials: MD
authors.lastname: Hernando
authors.forename: O
authors.initials: O
authors.lastname: Malato
authors.forename: M
authors.initials: M
authors.lastname: Farré
authors.forename: A R
authors.initials: AR
authors.lastname: Fernandez-Alba
authors.forename: D
authors.initials: D
authors.lastname: Barceló