Voltammetric determination of ethinylestradiol at a carbon paste electrode in the presence of cetyl pyridine bromine

Core-Shell Nanocables Decorated with Carbon Spherical Shells and Silver Nanoparticles for Sensing Ethinylestradiol Hormone in Water Sources and Pills

The selective, rapid detection of low levels of hormones in drinking water and foodstuffs requires materials suitable for inexpensive sensing platforms. We report on core-shell Ag@C nanocables (NCs) decorated with carbon spherical shells (CSSs) and silver nanoparticles (AgNPs) by using a hydrothermal green approach. Sensors were fabricated with homogeneous, porous films on screen-printed electrodes, which comprised a 115 nm silver core covered by a 122 nm thick carbon layer and CSSs with 168 nm in diameter. NCs and CSSs were also decorated with 10-25 nm AgNPs. The NC/CSS/AgNP sensor was used to detect ethinylestradiol using square wave voltammetry in 0.1 M phosphate buffer (pH 7.0) over the 1.0-10.0 μM linear range with a detection limit of 0.76 μM. The sensor was then applied to detect ethinylestradiol in tap water samples and a contraceptive pill with recovery percentages between 93 and 101%. The high performance in terms of sensitivity and selectivity for hormones is attributed to the synergy between the carbon nanomaterials and AgNPs, which not only increased the sensor surface area and provided sites for electron exchange but also imparted an increased surface area.

Characterization of laccases from Trametes hirsuta in the context of bioremediation of wastewater treatment plant effluent

The bioremediation of pharmaceutical compounds contained in wastewater, in an ecological and sustainable way, is possible via the oxidative action of fungal laccases. The discovery of new fungal laccases with unique physico-chemical characteristics pushes researchers to identify suitable laccases for specific applications. The aim of this study is to purify and characterize laccase isoenzymes produced from the Trametes hirsuta IBB450 strain for the bioremediation of pharmaceutical compounds. Two main laccases mixtures were observed and purified in the extracts and were called Yn and Yg. Peptide fingerprinting analysis suggested that Yn was constituted mainly of laccase Q02497 and Yg of laccase A0A6M5CX58, respectively. Robustness tests, based on tolerance and stability, showed that both laccases were affected in a relatively similar way by salts (KCl, NaCl), organic solvents (ACN, MeOH), denaturing compounds (urea, trypsin, copper) and were virtually unaffected and stable in wastewater. Determination of kinetic constants (Michaelis (KM), catalytic constant (kcat) and kinetic efficiency (K=kcat/KM)) for the transformation of synthetic hormone 17α-ethynylestradiol and the anti-inflammatory agent diclofenac indicates a lower KM and kcat for laccase Yn but relative similar K constant compared to Yg. Synergistic effects were observed for the transformation of diclofenac, unlike 17α-ethynylestradiol. Transformation studies of 17α-ethynylestradiol at different temperatures (4 and 21 °C) indicate a transformation rate reduction of approximately 75-80% at 4 °C against 25% for diclofenac in less than an hour. Finally, the classification of laccases Yg and Yn into one of eight groups (group A-H) suggests that laccase Yg belongs to group A (constitutive laccase) and laccase Yn belongs to group B (inducible laccase).

Advances on Hormones and Steroids Determination: A Review of Voltammetric Methods since 2000

This article presents advances in the electrochemical determination of hormones and steroids since 2000. A wide spectrum of techniques and working electrodes have been involved in the reported measurements in order to obtain the lowest possible limits of detection. The voltammetric and polarographic techniques, due to their sensitivity and easiness, could be used as alternatives to other, more complicated, analytical assays. Still, growing interest in designing a new construction of the working electrodes enables us to prepare new measurement procedures and obtain lower limits of detection. A brief description of the measured compounds has been presented, along with a comparison of the obtained results.

Multi sensor compatible 3D-printed electrochemical cell for voltammetric drug screening

3D printing is a hot topic in electroanalytical chemistry, allowing the construction of custom cells and sensors at affordable prices. In this work, we describe a novel small and practical 3D-printed electrochemical cell. The cell's body, manufactured in ABS on a 3D printer, is composed by three parts easily screwed: solution vessel, stick and cover with two embedded 3D-pen-printed carbon black-polylactic acid (CB-PLA) electrodes (counter and pseudo-reference). The cell is compatible with any planar working electrode, in which boron-doped diamond, graphite sheet (GS) and 3D-printed CB-PLA were shown as examples. A new alternative protocol to quickly produce 3D-printed sensors using a 3D pen and other low-cost apparatus is also proposed. The voltammetric performance of each evaluated sensor was carried out in the presence of redox probe ferricyanide and paracetamol as model analyte, and the surfaces were characterized by electrochemical impedance spectroscopy and scanning electrochemical microscopy. To present an analytical application of the 3D-printed cell, low-cost flexible sensors (GS and CB-PLA) were used as integrated platforms for sampling and detection of solid drugs. As a proof-of-concept, traces of drugs with a historic of counterfeit or adulteration (sildenafil citrate, tadalafil, losartan and 17α-ethinylestradiol) were abrasively sampled over the sensor and assembled on 3D-printed cell to perform a fast voltammetric scan in the presence of only 500 μL of electrolyte. This protocol is attractive for pharmaceutical and forensic sciences as a simple preliminary screening method which could identify the presence or absence of the suspicious drug as well as impurities or adulterants. The 3D-printed cell was also used for the determination of 17α-ethinylestradiol in a contraceptive pill to demonstrate a quantitative analysis. The cell is quickly printed (90 min), cheap (US$ 0.30) and requires low electrolyte volumes (0.5-3.0 mL), being suitable to be used in several other electroanalyses, especially for on-site applications.

Development of a portable electroanalytical method using nickel modified screen-printed carbon electrode for ethinylestradiol determination in organic fertilizers

Urine and struvite are organic fertilizers that have all nutritional requirements for the growth of a plant. However, these fertilizers may contain some emerging organic contaminants, such as ethinylestradiol, which is one of the most common hormones found in aquatic environments and can cause several changes in living organisms. Thus, the present study developed a fast, sensitive, inexpensive, and portable method for determining ethinylestradiol in urine and struvite, using square wave voltammetry (SWV) and screen-printed carbon electrodes modified with electrodeposited nickel film (SPCE-Ni). The electrodeposition of the nickel film on the screen-printed electrode was performed by cyclic voltammetry and optimized using complete factorial design 2³ and central composite design. The parameters optimized for SPCE-Ni were: number of cycles (1000); scan rate (5 V s^-1) and Ni²⁺ concentration (9.4 mmol L^-1). The operational parameters of the SWV for ethinylestradiol analysis were also optimized by experimental designs and obtained the following optimal values: step potential (10 mV), modulation amplitude (40 mV), and frequency (20 Hz). The method used 0.1 mol L^-1 BR buffer (pH 8.0) as support electrolyte and presented a limit of detection of 0.052 µmol L^-1 (R² = 0.996). Ethinylestradiol recovery test in struvite, human urine, synthetic urine, and pharmaceutical tablets ranged from 93.9% to 107.5%, indicating that there is no matrix effect. Furthermore, an interference test was performed with several drugs did not show any significant changes in the ethinylestradiol analytical signal, guaranteeing a greater precision of the method. These results reinforce the possibility of applying the proposed method in loco with a practical and fast way, without the need to use significant amounts of sample.

Voltammetric determination of ethinylestradiol using screen-printed electrode modified with functionalized graphene, graphene quantum dots and magnetic nanoparticles coated with molecularly imprinted polymers

The present work reports the development of a sensitive and selective method for ethinylestradiol detection using screen-printed electrode (SPE) modified with functionalized graphene (FG), graphene quantum dots (GQDs) and magnetic nanoparticles coated with molecularly imprinted polymers (mag@MIP). The performance of the mag@MIP sensor was compared with that of a non-molecularly imprinted sensor (mag@NIP). Chemical and physical characterizations of the mag@NIP and mag@MIP sensors were performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) techniques. The electrochemical behavior of the electrodes investigated, which included (mag@MIP)-GQDs-FG-NF/SPE, (mag@NIP)-GQDs-FG-NF/SPE, GQDs-FG-NF/SPE and FG-NF/SPE, was evaluated by cyclic voltammetry. The results obtained show a significant increase in peak current magnitude for (mag@MIP)-GQDs-FG-NF/SPE. Using square wave voltammetry experiments, the efficiency of the (mag@MIP)-GQDs-FG-NF/SPE sensor was also tested under optimized conditions. The linear response range obtained for ethinylestradiol concentration was 10 nmol L^-1 to 2.5 μmol L^-1, with limit of detection of 2.6 nmol L^-1. The analytical signal of the (mag@MIP)-GQDs-FG-NF/SPE sensor suffered no interference from different compounds and the sensor exhibited good repeatability. The proposed sensor was successfully applied for ethynilestradiol detection in river water, serum and urine samples, where recovery rates between 96 to 105% and 97-104% were obtained for environmental and biological samples, respectively.

Electrochemical study and simultaneous voltammetric determination of contraceptives ethinylestradiol and cyproterone acetate using silver nanoparticles solid amalgam electrode and cationic surfactant

In this work we propose the voltammetric analysis of contraceptive hormones ethinylestradiol (EE) and cyproterone acetate (CPA) using solid amalgam electrode fabricated with silver nanoparticles. To the best of our knowledge, this is the first report describing the simultaneous determination of these two compounds and also the first report of the use of amalgam electrode for analysis of EE and CPA. The voltammetric behavior of both substances was investigated by their reduction. An irreversible electrochemical process involving two protons and two electrons was found for each compound. The analytical assays were carried out using staircase voltammetry (SCV). Due to this, aiming to improve the analytical sensitivity, the cationic surfactant cetyltrimethylammonium bromide was also used. The instrumental and experimental parameters were studied and optimized to achieve the best conditions for the analysis. Under the optimum conditions, the voltammetric signals of EE and CPA showed dependence on the concentration range from 6.4 × 10^-7 to 7.8 × 10^-6 mol L^-1 and from 1.0 × 10^-6 to 1.0 × 10^-5 mol L^-1, respectively. The limits of detection obtained were 1.03 × 10^-7 mol L^-1 for EE and 2.99 × 10^-7 mol L^-1 for CPA. The analytical usefulness of the method was evaluated through its application on the simultaneous determination of EE and CPA in pharmaceutical formulations and urine samples. The two analytes were successfully quantified in these samples with good precision and the values found presented satisfactory concordance with the reference values, suggesting acceptable analytical efficiency for the approach described here.

Palladium Nanoparticles/Graphitic Carbon Nitride Nanosheets-Carbon Nanotubes as a Catalytic Amplification Platform for the Selective Determination of 17α-ethinylestradiol in Feedstuffs

A new kind of nanocomposite, graphitic carbon nitride (g-C₃N₄)-carbon nanotubes (CNTs), has been synthesized via solid grinding, and followed by thermal polymerization process of melamine and CNTs. Pd nanoparticles were loaded on the as-prepared nanocomposite by the self-assembly method. The Pd/g-C₃N₄-CNTs nanocomposite exhibited excellent electrocatalytic activity toward the oxidation of 17α-ethinylestradiol (EE2), and compared with other detection methods of EE2, such as HPLC, this detection platform does not need the samples for further purification processing. And this detection platform was compared with HPLC, there is no significant difference between two methods, and the accuracy and precision of the determination of EE2 in feedstuff sample by differential pulse voltammetry (DPV) to a satisfactory level. Thus, the Pd/g-C₃N₄-CNTs nanocomposite can be used as a signal amplification platform for the detection of EE2 in feedstuffs samples. Under the optimum condition, the current response increased linearly with EE2 concentration from 2.0 × 10⁻⁶ ~ 1.5 × 10⁻⁴ M with a detection limit of 5.0 × 10⁻⁷ M (S/N = 3) by DPV. The Pd/g-C₃N₄-CNTs showed good reproducibility and excellent anti-interference ability that the relative standard deviation was 3.3% (n = 5). This strategy may find widespread and promising applications in other sensing systems involving EE2.

Development of Electrochemical Sensor Based on Carbonaceal and Metal Phthalocyanines Materials for Determination of Ethinyl Estradiol

This work describes the development of an electrochemical sensor that was used in the determination of ethinyl estradiol (EE) in pharmaceutical formulations, river water, and milk using the square wave voltammetry technique. Studies were carried out using different carbonaceous materials (multiwalled carbon nanotubes, reduced graphene oxide Reduced graphene oxide, graphite) and different metallic phthalocyanines (cobalt, iron and manganese). Based on these studies it was possible to obtain the best system for the construction of the sensor. The device was obtained by the chemical modification of a glassy carbon electrode (GCE) with multiwalled carbon nanotubes (MWCNTs) and cobalt phthalocyanine (CoPc). The materials were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Under conditions previously optimized for the proposed method, an analytical curve was constructed, presenting linearity in a range of 2.50–90.0 μmol L−1 (R = 0.990), with detection limit of 2.20 μmol L−1 and quantification of 2.50 μmol L−1. The validation of the methodology for the determination of EE using GCE-MWCNTs-CoPc was performed, being accurate, precise, stable and sensitive. The recovery of ethinyl estradiol in the sample of pharmaceutical formulation was 103.93%, in the samples of river water ranged from 92.75% to 96.47%, and in the milk sample was from 88.00% to 96.20%. Thus, the proposed method presented a viable alternative for the determination of ethinyl estradiol in the quality control of pharmaceutical and food formulations as well as in environmental control.

Rapid Screening Method for Detecting Ethinyl Estradiol in Natural Water Employing Voltammetry

17α-Ethinyl estradiol (EE2), which is used worldwide in the treatment of some cancers and as a contraceptive, is often found in aquatic systems and is considered a pharmaceutically active compound (PhACs) in the environment. Current methods for the determination of this compound, such as chromatography, are expensive and lengthy and require large amounts of toxic organic solvents. In this work, a voltammetric procedure is developed and validated as a screening tool for detecting EE2 in water samples without prior extraction, clean-up, or derivatization steps. Application of the method we elaborate here to EE2 analysis is unprecedented. EE2 detection was carried out using differential pulse adsorptive cathodic stripping voltammetry (DP AdCSV) with a hanging mercury drop electrode (HMDE) in pH 7.0 Britton-Robinson buffer. The electrochemical process of EE2 reduction was investigated by cyclic voltammetry at different scan rates. Electroreduction of the hormone on a mercury electrode exhibited a peak at -1.16 ± 0.02 V versus Ag/AgCl. The experimental parameters were as follows: -0.7 V accumulation potential, 150 s accumulation time, and 60 mV s^-1 scan rate. The limit of detection was 0.49 μg L^-1 for a preconcentration time of 150 s. Relative standard deviations were less than 13%. The method was applied to the detection of EE2 in water samples with recoveries ranging from 93.7 to 102.5%.

Analysis for estrogens as environmental pollutants--a review

The approaches to the analysis for estrogen compounds as environmental pollutants are critically reviewed and evaluated on the basis of significant, recent original publications. The importance of sample pretreatment and analyte preconcentration techniques is pointed out, with an emphasis on SPE and on the use of highly selective interactions such as molecular recognition. The hyphenated systems of high-performance gas or liquid chromatography and mass spectrometric techniques are discussed as the basic methods of determination of estrogens in environmental samples. Immunochemical procedures are shown to be useful in semiquantitative screening of estrogen pollutants (e.g. ELISA kits). Classical HPLC and GC with common UV/Vis, fluorescence and electrochemical detection are useful in routine checking on higher pollutant concentrations.