Comparison of Two Estrogen CALUX Cell Bioassays to Liquid Chromatography-Mass Spectrometry for Quantifying Estrone in Water Samples.

Chemically activated luciferase expression (CALUX) cell bioassays are popular tools for assessing endocrine activity of chemicals such as certain environmental contaminants. Although activity equivalents can be obtained from CALUX analysis, directly comparing these equivalents to those obtained from analytical chemistry methods can be problematic due to the complexity of endocrine active pathways. We explored the suitability of two estrogen CALUX bioassays (the OECD-approved VM7Luc4E2 cell bioassay and the VM7LucERβc9 cell bioassay) for quantitation of estrogen. Quadrupole-time of flight ultraperformance liquid chromatography/mass spectrometry (LC/MS) was selected as a comparative method. Regression analysis of measured estrone (E1) calibration samples showed all three methods as highly predictive of nominal concentrations (p ≤ 7.5 x 10 -51 ). Extracts of water sampled from laboratory dilutor tanks containing estrone (E1) at 0, 20, and 200 ng/L alone, and in combination with atrazine (ATZ) were selected to test the quantitative capabilities of the CALUX assays. Process controls (0 and 100 ng E1/L) and a separate E1 standard (10 ng/mL, used to prepare the E1 process control) were also tested. E1 levels determined by LC/MS analysis and bioanalytical equivalents (BEQ, ng E1/L) determined by CALUX analyses were comparable except in certain instances where the samples required dilution prior to CALUX analyses (e.g., the E1 process control and E1 standard). In those instances, measurements by CALUX were slightly but significantly decreased relative to LC/MS. ATZ had no effect on the ability of either LC/MS or the CALUX bioassays to quantify E1. This study illustrates the CALUX bioassays as successful in quantifying an estrogen in simple water samples and further characterizes their utility for screening. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2022;00:0-0. © 2022 SETAC.