Development and Validation of a HPLC‐DAD Method for Determination of Several Endocrine Disrupting Compounds in Estuarine Water

Abstract

This paper presents the development and validation of an analytical procedure, which allows the simultaneous quantification of nine endocrine disrupters (EDCs) in polluted surface waters. The compounds selected for this study were the natural hormones (17β‐estradiol and estrone), the synthetic hormone (17α‐ethynylestradiol), the bisphenol A, the alkylphenols (4‐octylphenol and 4‐nonylphenol), and the phytoestrogens (daidzein, genistein, and biochanin A). Briefly, this method consisted of the preconcentration of water samples (2 L) in 500 mg Oasis HLB cartridges, followed by a cleanup step in 1 g silica cartridges, and analysis of all EDCs by High Performance Liquid Chromatography with Diode Array Detection (HPLC‐DAD). The chromatographic separation occurred in a RP‐18 analytical column in a gradient mode of CH₃CN:H₂O (pH 2) at a flow rate of 1 mL/min. The validation parameters revealed that this method was highly specific for all assayed EDCs (>99%), the linearity of the calibration curves, obtained either by external patronization or by fortified matrix calibration techniques, always showed a correlation higher than 0.99 and their intermediate precision and repeatability, evaluated in terms of intra and inter assays, were optimal for all EDCs (RSD<3%). The precision and accuracy, estimated as the recovery rates that occurred during the preconcentration and the cleanup processes showed, for all EDCs, excellent results (RSD<3% and recoveries up to 116%), and preconcentration factors (enrichment) up to 10000. The limits of detection (LOD) and quantification (LOQ) were mathematically estimated from the calibration curves. As expected, these values were different for each of the nine assayed EDCs and were higher when calculated from the addition standard calibration curves. Here, 4‐octylphenol was the compound with the lowest LOD and LOQ (3.8 ng/L and 12.0 ng/L) and 17α‐ethynylestradiol the one with the highest levels for both cited parameters (18.0 ng/L and 54.5 ng/L). Finally, the performance of the method was checked with water samples from a highly polluted area in the Douro river estuary (Portugal). The field results revealed high levels of estrogens (up to 176 ng/L), bisphenol A (up to 5.1 µg/L), alkylphenols (up to 449 ng/L), and phytoestrogens (up to 74 ng/L), in accordance with the high local pollution load, and suggested that this method can be easily and successfully used in water monitoring surveys of, at least, highly polluted estuarine areas.

Keywords:

• Method validation
• HPLC-DAD
• Water analysis
• Environmental estrogenic compounds

Acknowledgments

This study was financially supported by the Fundação para a Ciência e Tecnologia, (PhD Grant SFRH/BD/18231/2004/SLU) and by Cooperativa de Ensino Superior, Politécnico e Universitário, CRL (CESPU)/ISCS‐N (Research Projects 1F/13/2005/CESPU and 2F/02/2006/CESPU).