TY - JOUR A1 - Silva, C.P. A1 - Lima, D.L.D. A1 - Schneider, Rudolf A1 - Otero, M. A1 - Esteves, V.I. T1 - Development of ELISA methodologies for the direct determination of 17beta-estradiol and 17alpha-ethinylestraydiol in complex aqueous matrices N2 - This study comprises the development of enzyme-linked immunosorbent assays (ELISAs) for the quantification of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) in complex aqueous matrices without any sample clean-up procedures. Salinity and dissolved organic matter were selected as potential interfering agents in the analysis of E2 and EE2. The optimization was performed in order to (i) overcome matrix effects, and to (ii) increase sensitivity. The addition of a sample buffer containing bovine serum albumin (BSA) prior to the sample was found to decrease the influence of matrix effects. Moreover, adjustments of this buffer's pH together with the optimization of tracer (T) dilution and incubation time were undertaken in order to lower the quantification range. The optimized methods allowed the quantification of E2 and EE2 in the ranges 0.03–200 µg L-1 and 0.02–10 µg L-1, respectively. The assays were applied to real aqueous samples. It was possible to do a first approach to the levels of E2 in Portuguese surface and waste waters; however, it was not feasible to detect EE2 in the samples tested. KW - Enzyme-linked immunosorbent assay KW - Endocrine disrupting compounds KW - 17beta-Estradiol KW - 17alpha-Ethinylestradiol KW - Surface water KW - Wastewater PY - 2013 DO - https://doi.org/10.1016/j.jenvman.2013.03.041 SN - 0301-4797 SN - 1095-8630 VL - 124 SP - 121 EP - 127 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-28516 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 DO - 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 - TY - JOUR A1 - Stebbings, R. A1 - Wang, L. A1 - Sutherland, J. A1 - Kammel, M. A1 - Gaigalas, A.K. A1 - John, M. A1 - Roemer, B. A1 - Kuhne, Maren A1 - Schneider, Rudolf A1 - Braun, M. A1 - Engel, A. A1 - Dikshit, D.K. A1 - Abbasi, F. A1 - Marti, G.E. A1 - Sassi, M.P. A1 - Revel, L. A1 - Kim, S.-K. A1 - Baradez, M.-O. A1 - Lekishvili, T. A1 - Marshall, D. A1 - Whitby, L. A1 - Jing, W. A1 - Ost, V. A1 - Vonsky, M. A1 - Neukammer, J. T1 - Quantification of cells with specific phenotypes I: Determination of CD4+ cell count per microliter in reconstituted lyophilized human PBMC prelabeled with anti-CD4 FICT antibody N2 - A surface-labeled lyophilized lymphocyte (sLL) preparation has been developed using human peripheral blood mononuclear cells prelabeled with a fluorescein isothiocyanate conjugated anti-CD4 monoclonal antibody. The sLL preparation is intended to be used as a reference material for CD4+ cell counting including the development of higher order reference measurement procedures and has been evaluated in the pilot study CCQM-P102. This study was conducted across 16 laboratories from eight countries to assess the ability of participants to quantify the CD4+ cell count of this reference material and to document cross-laboratory variability plus associated measurement uncertainties. Twelve different flow cytometer platforms were evaluated using a standard protocol that included calibration beads used to obtain quantitative measurements of CD4+ T cell counts. There was good overall cross-platform and counting method agreement with a grand mean of the laboratory calculated means of (301.7 ± 4.9) µL-1 CD4+ cells. Excluding outliers, greater than 90% of participant data agreed within ±15%. A major contribution to variation of sLL CD4+ cell counts was tube to tube variation of the calibration beads, amounting to an uncertainty of 3.6%. Variation due to preparative steps equated to an uncertainty of 2.6%. There was no reduction in variability when data files were centrally reanalyzed. Remaining variation was attributed to instrument specific differences. CD4+ cell counts obtained in CCQM-P102 are in excellent agreement and show the robustness of both the measurements and the data analysis and hence the suitability of sLL as a reference material for interlaboratory comparisons and external quality assessment. KW - CD4+ cell counting KW - Relative concentration measurement KW - Lyophilized cells KW - Flow cytometry KW - Standard measurement procedure KW - Measurement of uncertainty KW - Human immunodeficiency virus-1 KW - Acquired immunodeficiency syndrome KW - Reference material PY - 2015 DO - https://doi.org/10.1002/cyto.a.22614 SN - 0196-4763 SN - 1552-4922 SN - 1552-4930 VL - 87 IS - 3 SP - 244 EP - 253 PB - Wiley-Liss CY - Hoboken, NJ AN - OPUS4-32847 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -