Examinando por Materia "Chitosan"
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- PublicaciónSólo datosA new and simple electroanalytical method to detect thiomersal in vaccines on a screen-printed electrode modified with chitosan(Analytical Methods, 2018-03-02) González, Camila; García-Beltrán, Olimpo; Nagles, EdgarThe use of a screen-printed electrode modified with chitosan (Cs) to determine thiomersal (TMS) through the oxidation of thiosalicylic acid by linear sweep anodic stripping voltammetry is reported for the first time in this work. The screen-printed electrode was coated with chitosan (Cs/SPCE) and the surface was studied with cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode presented activity towards the oxidation of thiomersal (TMS) at 0.24 V. The signal is the product of the oxidation of the thiosalicylic acid or organic part and not of the mercury in the chemical structure of thiomersal. Optimal parameters for linear sweep anodic stripping voltammetry were pH 3.2 in phosphate buffer solution (PBS), accumulation time (tACC) 90 s, accumulation potential (EACC) −1.0 V and scan rate 100.0 mV s−1; the oxidation signal was proportional to the concentration of TMS between 0.99 and 10.90 μmol L−1, with a detection limit of 0.038 μmol L−1 and the relative standard deviation (RSD) was 5.0% using seven different electrodes. The sensor was used in human urine samples spiked with thiomersal and commercial cattle vaccines with consistent results.
- PublicaciónSólo datosDetection of Sunset Yellow by Adsorption Voltammetry at Glassy Carbon Electrode Modified with Chitosan(2018-04-10) García-Beltrán, Olimpo; Nagles, Edgar; Peña-Gonzalez, AndresThe simple modification of the surface of a glassy carbon electrode with chitosan (CS) allowed the development of a electroanalytical method useful for the detection and quantification of sunset yellow (SY-E110) by square wave adsorption voltammetry (SWAdV). The electrode surface was characterized with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results showed that the presence of CS on the surface of the electrode, allowed the oxidation of the SY to 1.01 V in a process controlled by adsorption. Under optimal conditions (pH 2.5, tADS 60s, EADS 0.10 V) the anodic peak current was proportional to the concentration of SY between 0.25 to 3.25 μmol L-1, with a limit of detection of 0.098 μmol L-1. The relative standard deviation (RSD) for a solution with 0.080 mmol L-1 of E110 was 2.5% for five different electrodes (n=5). The method was validated with unflavored gelatin samples spiked with known amounts of SY. The potential interferences of other synthetic dyes were studied and finally the method was tested with real samples of foods containing SY and other synthetic dyes. The results were equally acceptable compared to previous reports.
- PublicaciónSólo datosDevelopment of an Electrochemical Sensor to Detect Dopamine and Ascorbic Acid Based on Neodymium (III) Oxide and Chitosan(Electroanalysis, 2017-01-12) Nagles, Edgar; Calderón, Jorge A.; García-Beltrán, OlimpoNeodymium (III) oxide (Nd Ox ) was dispersed in chitosan dissolution and deposited on a glassy carbon electrode (chitosan-Nd Ox /GCE). The surface properties of the chitosan-Nd Ox /GCE were evaluated with FeCN 6 −3 solution using cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode was used in the determination of individual dopamine (DP) and ascorbic acid (AA) with square wave adsorptive voltammetry. Under optimal parameters (pH 4.0; accumulation time; t ACC 60s and accumulation potential; E ACC 0.10 V) for DP and (pH 3,0; t ACC 60s and; E ACC −0.20 V) for AA, anodic peak currents were proportional to the concentration of DP and AA between 0.90 and 17.0 μmolL −1 , with detection limit of 0.079 μmolL −1 for DP and 0.12 μmolL −1 for AA. The sensor was used in the determination of DP and AA in human urine samples and vitamin C tablets with consistent results. The new sensor is easy to develop. In addition, the sensitivity in particular for AA was improved compared with previous work.
- PublicaciónSólo datosNew combination between chitosan, single walled carbon nanotubes and neodymium(III) oxide found to be useful in the electrochemical determination of rutin in the presence of morin and quercetin(Analytical Methods, 2017-11-11) Calderón, Jorge A.; Cardozo-Pérez, María; Torres-Benítez, Alfredo; García-Beltrán, Olimpo; Nagles, EdgarA glassy carbon electrode surface was modified with a new combination of chitosan, single walled carbon nanotubes (SWCNT) and neodymium(III) oxide (NdOX) and was found to be effective in the detection of rutin (RU), a natural antioxidant. The modified electrode displayed high activity toward the oxidation of RU compared to other flavonoids, such as quercetin (Q) and morin (MO). The oxidation peaks of RU, MO and Q were exhibited at +0.53, +0.42 and +0.39 V, respectively. Moreover, anodic peak currents were 37.27, 10.39 and 2.27 μA, respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrode surface, and square wave voltammetry (SWV) was used to quantify RU. The detection limit (3σ/b) was 0.092 μmol L−1, and the RSD was 2.5%. A new sensor was used in the quantification of RU in roasted beans infusion of Coffea arabiga L. and extract of Zamia furfuracea L.f. ex Aiton with satisfactory results.