“…The slope 0.054 V/pH was close to the theoretical value given by the Nernst equation [ 33 ], suggesting that the reduction of phoxim involves the transfer of equal number of protons and electrons according to Scheme 2 electrode [ 12 ]. Scheme 2 Mechanism of phoxim reduction.…”
In this study, cobalt nanoparticles (CoNPs) were synthesized and cobalt nanoparticles modified glassy carbon electrode (CoNPs/GCE) was prepared by drop coating the nanoparticles on glassy carbon electrode. After preparing polypyrrole modified glassy carbon electrode (PPy/GCE) using electropolymerization of pyrrole in LiClO
4
solution, cobalt nanoparticles-polypyrrole composite modified glassy carbon electrode (CoNPs/PPy/GCE) was fabricated by drop coating the CoNPs on the PPy/GCE. Different characterization techniques such as scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, FTIR spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry were used to study the morphological structure and electrochemical behavior of the sensors. The results demonstrated that PPy chains interacted with CoNPs through donor-acceptor bonds. Among all the electrodes, CoNPs/PPy/GCE exhibited highest electroactive surface area and lowest electron transfer resistance towards phoxim. Under the optimal conditions, the sensor showed linear relationship between the reduction peak current and the concentration of phoxim in the range of 0.025 μM–12 μM with the detection limit as 4.5 nM. Besides, the composite electrode demonstrated excellent reproducibility, good stability and selectivity towards the possible interfering substances. All of these properties made CoNPs/PPy/GCE a suitable electrochemical sensor for the electrochemical determination of phoxim in water samples using square wave voltammetry.
“…The slope 0.054 V/pH was close to the theoretical value given by the Nernst equation [ 33 ], suggesting that the reduction of phoxim involves the transfer of equal number of protons and electrons according to Scheme 2 electrode [ 12 ]. Scheme 2 Mechanism of phoxim reduction.…”
In this study, cobalt nanoparticles (CoNPs) were synthesized and cobalt nanoparticles modified glassy carbon electrode (CoNPs/GCE) was prepared by drop coating the nanoparticles on glassy carbon electrode. After preparing polypyrrole modified glassy carbon electrode (PPy/GCE) using electropolymerization of pyrrole in LiClO
4
solution, cobalt nanoparticles-polypyrrole composite modified glassy carbon electrode (CoNPs/PPy/GCE) was fabricated by drop coating the CoNPs on the PPy/GCE. Different characterization techniques such as scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, FTIR spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry were used to study the morphological structure and electrochemical behavior of the sensors. The results demonstrated that PPy chains interacted with CoNPs through donor-acceptor bonds. Among all the electrodes, CoNPs/PPy/GCE exhibited highest electroactive surface area and lowest electron transfer resistance towards phoxim. Under the optimal conditions, the sensor showed linear relationship between the reduction peak current and the concentration of phoxim in the range of 0.025 μM–12 μM with the detection limit as 4.5 nM. Besides, the composite electrode demonstrated excellent reproducibility, good stability and selectivity towards the possible interfering substances. All of these properties made CoNPs/PPy/GCE a suitable electrochemical sensor for the electrochemical determination of phoxim in water samples using square wave voltammetry.
This paper describes an electroanalytical method for the determination of rapamycin using a pretreated pencil graphite electrode (P‐PGE) by differential pulse voltammetry. The electrodes were successfully characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, and Fourier transform infrared. The influences of instrumental and chemical parameters were investigated and optimized for the determination of rapamycin. Oxidation peak current obtained for rapamycin at P‐PGE was 10.5 times higher than that obtained for PGE. In pH = 3.0 H3PO4, a well‐defined irreversible anodic peak occurred at 1.07 V, which was attributed to the electro‐oxidation of rapamycin at P‐PGE. Under optimized conditions, the oxidation peak current of rapamycin was linear with its concentration in the range of 0.01–250 μmol/L, and the detection limit was 0.0075 μmol/L (S/N = 3). Also, the P‐PGE exhibited good reproducibility (relative SD [RSD] = 2.17% for 10 electrodes at different times using the same procedure), repeatability (RSD = 2.09% for 10 measurements with same electrode), and stability (95.80% for 10 days). The P‐PGE was simple to prepare and the method was successfully applied for the determination of rapamycin in spiked and real samples. In addition, for comparison, high‐performance liquid chromatographic method with ultraviolet (UV) detector was used for the determination of rapamycin.
“…BPA is a primary component of polycarbonate (PC) plastic, which is an epoxy resin monomer (Li et al, 2010;Muhamad et al, 2016;Rubin, 2011) and is used with phthalates in food and beverage containers, including bottles for drinking water (Fadillah et al, 2020).…”
To identify the factors that influence the presence and quantification of endocrine disruptors (EDs) in bottled water marketed in Bogotá, the packaging (plastic or glass), gas (sparkling or still water) and origin (international or Colombian) of the water were considered. EDs were divided into plasticizers, drugs and hormones and were quantitatively determined via gas chromatography coupled to mass spectrometry (GC-MS).Principal component and multiple correspondence analyses, the Wilcoxon and Kruskal-Wallis tests, average mutual information and tree-based models were used to identify the factors that affected the ED concentrations. Phthalates, drugs, hormones and synthetic compounds were detected, including 4-tert-octylphenol, acetaminophen, caffeine, fluoxetine, gemfibrozil, triclosan, bisphenol A, primidone, carbamazepine and progesterone. Factors such as glass packaging and sparkling water increased the detection and presence of EDs. Fourteen of the 16 identified compounds were detected if the water was bottled in glass; the exceptions were caffeine and acetaminophen. Furthermore, bottled water of international origin had higher concentrations of most EDs than Colombian bottled water. The statistical approaches used are an innovative predictive method for analysing ED concentrations and classifying factors closely correlated with the presence of these compounds.
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