Application of dispersive liquid-liquid microextraction for estrogens' quantification by enzyme-linked immunosorbent assay.
Estrogens, such as 17β-estradiol (E2) and 17α-ethinylestradiol (EE2), are the major responsible for endocrine-disrupting effects observed in aquatic environments due to their high estrogenic potency, even at concentrations ranging from pgL(-1) to ng L(-1). Thus, it is essential to develop analytical methodologies suitable for monitoring their presence in water samples. Dispersive liquid-liquid microextraction (DLLME) was used as a pre-concentration step prior to the quantification of E2 and EE2 by enzyme-linked immunosorbent assay (ELISA). First, an evaluation of the effect of DDLME on the E2 and EE2 ELISA calibration curves was performed. Since the extraction procedure itself had an influence on the ELISA optical density (OD), it became necessary to subject, not only the samples, but also all the standards to the DLLME process. Working ranges were determined, being between 1.2 and 8000 ng L(-1), for E2, and between 0.22 and 1500 ng L(-1), for EE2. The influence of organic matter, both in the extraction and quantification, was evaluated and it was observed that its presence in the solution did not affect considerably the calibration curve. Recovery rates were also determined, ranging from 77% to 106% for ultrapure water and from 104% to 115% for waste water samples, the most complex ones in what concerns matrix effects. Results obtained when applying the proposed method to real water samples can be considered quite satisfying. Moreover, the obtained working ranges encompass values generally reported in literature, confirming the practical use of the method for environmental samples.
CESAM & Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal; Department of Complementary Sciences, College of Health Technology of Coimbra, Rua 5 de Outubro S. Martinho do Bispo Apartado 7006, 3040-854 Coimbra, Portugal. Electronic address: diana.lima@ua.pt.
Diana L D
DL
Lima
CESAM & Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
Carla Patrícia
CP
Silva
BAM Federal Institute for Materials Research and Testing, Department of Analytical Chemistry, Reference Materials, Richard-Willstaetter-Str. 11, D-12489 Berlin, Germany.
Rudolf J
RJ
Schneider
CESAM & Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal; Department of Applied Chemistry and Physics, University of León, Campus de Vegazana, 24071 León, Spain.
Marta
M
Otero
CESAM & Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
Valdemar I
VI
Esteves
D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D004797:Enzyme-Linked Immunosorbent Assay; D004958:Estradiol / Q000032:analysis*; D004967:Estrogens / Q000737:chemistry*; D004997:Ethinyl Estradiol / Q000032:analysis*; D059627:Liquid Phase Microextraction; D009930:Organic Chemicals / Q000737:chemistry; D015203:Reproducibility of Results; D052616:Solid Phase Extraction; D014867:Water / Q000032:analysis / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
D004967:Estrogens; D009930:Organic Chemicals; D014867:Water; D004997:Ethinyl Estradiol; D004958:Estradiol
17α-ethinylestradiol; 17β-estradiol; DLLME; ELISA; Environment; Water samples