Determination of trace endocrine disruptors in ultrapure water for laboratory use by the yeast estrogen screen (YES) and chemical analysis (GC/MS)

High purity water for endocrine disruptors (EDs) analysis in experimental tests is an indispensable requirement for the preparation of reagents and solutions employed in biological laboratories. Commercial ultrapure water may contain traces of organic compounds, which can interfere with in vitro bioassays carried out to detect the potential estrogen-like activity of pure compounds and complex mixtures. This paper shows that solid-phase extracts of different types of ultrapure water (UPW) purchased or produced in situ for laboratory analysis (mQ-UPW) may contain organic molecules able to antagonize the binding of E₂ to the human estrogen receptor α in the yeast estrogen screen (YES) assay. GC/MS analysis detected the presence of bis(2-ethylhexyl) phthalate (DEHP) (0.033 ppm ± 0.006) in mQ-UPW extracts. The dose–response curve of DEHP in the YES assay showed a relevant antagonist effect of this phthalate. Agreement between content of DEHP chemically detected in UPW extract and the magnitude of biological effects induced was pointed out. It would be appropriate that chemical analyses were complemented by biological tests to establish concentration limits for chemical contaminants in UPW that do not induce biological effects detectable in vitro. The yeast assay used in this study has previously proved to be a sensitive tool in assessing the presence of agonistic/antagonistic chemicals at the ng/l level in complex mixtures and may be successfully used to identify trace amounts of estrogenic/antiestrogenic chemicals, which can represent critical issues influencing the experimental results in environmental testing laboratories.