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- Ethinylestradiol (3) (entfernen)
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The synthetic estrogen ethinylestradiol (EE2) is an active component of oral contraceptives (OCs), considered as an endocrine disrupting compound (EDC). It is excreted from humans and released via sewage treatment plant effluents into aquatic environments. EDCs are any environmental pollutant chemical that, once incorporated into an organism, affects the hormonal balance of various species including humans. Its presence in the environment is becoming of great importance in water quality. This paper describes the development of an accurate, sensitive and selective method for capture, preconcentration and determination of EE2 present in water samples using: magnetic particles (MPs) as bioaffinity support for the capture and preconcentration of EE2 and a glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNTs/GCE) as detection system. The capture procedure was based on the principle of immunoaffinity, the EE2 being extracted from the sample using the anti-EE2 antibodies (anti-EE2 Ab) which were previously immobilized on MPs. Subsequently the analyte desorption was done employing a sulfuric acid solution and the determination of the EE2 in the pre-concentrated solution was carried out by square wave voltammetry (SWV).
This method can be used to determine EE2 in the range of 0.03570 ng L-1 with a detection limit (LOD) of 0.01 ng L-1 and R.S.D. < 4.20%. The proposed method has been successfully applied to the determination of EE2 in water samples and it has promising analytical applications for the direct determination of EE2 at trace levels.
In this work, we report an electrochemical immunosensor to detect ethinylestradiol in water samples, using electrochemical impedance spectroscopy (EIS) as a detection technique. For the development of this immunosensor, the direct modification of the working electrode of a screen-printed carbon electrode was carried out. First, to reduce the resistance of the electrode, electroreduced graphene was incorporated on the surface.
Second, a porous gold structure was electrodeposited on reduced graphene by electrodeposition and the dynamic hydrogen bubble template assisted method. Thus, a marked increase in surface area was obtained for anti-EE2 antibodies immobilization. Subsequently, the specific anti-EE2 antibodies were covalently immobilized using α-lipoic acid for attaching them to the gold surface.
The electrode modified with the antibodies was incubated for 30 min in the samples containing EE2, producing the specific Antigen antibody binding. As the charge transfer resistance of a redox probe in the electrode surface is governed by the surface blocking effects, the charge transfer resistance was related to the amount of EE2 captured to realize a quantitative determination. For this, the EIS measurements were performed in a 4 mM [Fe(CN)6]4−/3− solution in 0.1 M KCl. The obtained Nyquist diagrams were adjusted using the Randles circuit as an equivalent circuit to obtain the corresponding resistances. The developed methodology showed good selectivity, precision, and sensitivity; although the LOD obtained was higher than those presented in other published articles, it turned out to be an alternative that allows the determination of ethinylestradiol using a simple disposable electrode.
In this work, we have developed and characterized a novel microfluidic immunoassay methodology for rapid and sensitive quantification of ethinylestradiol (EE2) in river water samples. The detection of EE2 was carried out using a competitive direct immunoassay method based on the use of anti-EE2 polyclonal antibodies immobilized on magnetic microspheres 3-aminopropyl-modified manipulated for an external removable magnet. The EE2 present in the water sample was allowed to compete with EE2-horseradish peroxidase (HPR) conjugated for the immobilized anti-EE2 antibody. The HPR, in the presence of hydrogen peroxide (H2O2) catalyzes the oxidation of catechol (Q) whose back electrochemical reduction was detected on gold electrode at 0.0 V. The response current obtained from the product of enzymatic reaction is inversely proportional to the amount of EE2 in the water sample. The electrochemical detection can be done within 1 min and total assay time was 30 min. The calculated detection limits for electrochemical detection and the ELISA procedure are 0.09 and 0.32 ng L-1 respectively and the intra- and inter-assay coefficients of variation were below 5.8%. Our electrochemical immunosensor showed higher sensitivity and lower time consumed than the standard spectrophotometric detection ELISA method, which shows the potential for assessment of EE2 in river water samples.