TY - JOUR A1 - Silva, C.P. A1 - Lima, D.L.D. A1 - Schneider, Rudolf A1 - Otero, M. A1 - Esteves, V.I. T1 - Evaluation of the anthropogenic input of caffeine in surface waters of the north and center of Portugal by ELISA N2 - This study comprises the development of an enzyme-linked immunosorbent assay (ELISA) for the quantification of caffeine in complex aqueous matrices without any sample clean-up procedure. Salinity and dissolved organic matter were selected as potential interfering agents. The addition of a sample buffer containing bovine serum albumin (BSA) prior to the sample was found to decrease the influence of those interfering agents. The working range of the developed method was 0.1–100 µg L- 1. Quantification of caffeine was possible in 43 out of 51 real aqueous samples, at values between < LOD and 15 µg L- 1. Results correlate well with those obtained by LC–MS/MS. To the best of our knowledge this is the first study dealing with the quantification of caffeine in Portugal's surface waters. KW - Caffeine KW - Surface water KW - ELISA KW - Anthropogenic markers KW - Koffein KW - Eintrag KW - Oberflächenwasser KW - Gewässer KW - Abwasser KW - Antikörper KW - Immunoassay PY - 2014 U6 - https://doi.org/10.1016/j.scitotenv.2014.01.120 SN - 0048-9697 VL - 479-480 SP - 227 EP - 232 PB - Elsevier CY - Amsterdam AN - OPUS4-30450 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lima, D.L.D. A1 - Silva, C.P. A1 - Schneider, Rudolf A1 - Otero, M. A1 - Esteves, V.I. T1 - Application of dispersive liquid-liquid microextraction for estrogens' quantification by enzyme-linked immunosorbent assay N2 - 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 pg L-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. KW - DLLME KW - ELISA KW - Water samples KW - Environment KW - 17beta-estradiol KW - 17alpha-ethinylestradiol PY - 2014 U6 - https://doi.org/10.1016/j.talanta.2014.02.069 SN - 0039-9140 VL - 125 SP - 102 EP - 106 PB - Elsevier CY - Amsterdam AN - OPUS4-30614 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lima, D.L.D. A1 - Silva, C.P. A1 - Schneider, Rudolf A1 - Esteves, V.I. T1 - Development of an ELISA procedure to study sorption of atrazine onto a sewage sludge-amended luvisol soil N2 - Pesticides may contaminate ground and surface waters and one of the major factors governing this property is soil sorption. Sorption can be assessed by batch equilibrium technique which produces lots of extracts with high dissolved organic carbon concentration in which the pesticide concentration has to be determined. We developed an ELISA procedure to analyse atrazine based on polyclonal antibodies (C193) for which tracer structure and dilutions of immunochemical reagents were adapted to fit the purpose. After a 1000-fold dilution (or after an SPE clean-up procedure) extracts of a sewage-sludge amended luvisol (used as an example application of the methodology developed) could be reliably analysed. The Freundlich model is able to describe adsorption for this system (r² = 0.977) delivering a distribution coefficient KF of 1.6 ± 0.2 (mg kg-1) (mg L-1)-N and an isotherm nonlinearity factor N of 0.70 ± 0.09. KW - ELISA KW - Atrazine KW - Sorption PY - 2011 U6 - https://doi.org/10.1016/j.talanta.2011.06.024 SN - 0039-9140 VL - 85 IS - 3 SP - 1494 EP - 1499 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-24305 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -