Examinando por Autor "Calderón, Jorge A."
Mostrando1 - 10 de 10
Resultados por página
Opciones de clasificación
- PublicaciónSólo datosCarbon Paste Composite with Co3O4 as a New Electrochemical Sensor for the Detection of Allura Red by Reduction(Electroanalysis, 2019-04-15) Penagos Llanos, Johisner; García-Beltrán, Olimpo; Calderón, Jorge A.; Nagles, Edgar; Hurtado, JhonThe detection of Allura red (AR) by electrochemical reduction using a different electrode from the conventional mercury electrode is presented. A carbon paste with cobalt (II, III) oxide composite electrode (CoOx/CPE) is reported for the first time for the detection of AR. Moreover, others dyes such as tartrazine (TZ), sunset yellow (SY), amaranth (AM), Ponceaut 4‐R (P‐4R), and Sudan (SD) as well as pharmaceutical agents such as paracetamol (PMC) that are present in samples that contained AR did not show a reduced signal between 0.0 and −0.3 V, which is the potential range where AR reduction was observed. The surface electroactivity was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The presence of CoOX increased the cathodic peak current for AR by more than 50 % and 65 % via CV and square wave voltammetry (SWV), respectively, compared with an unmodified carbon paste electrode. Under the optimal parameters, (pH=3.0, accumulation time (tACC)=60 s and accumulation potential (EACC)=0.50 V), the detection limit for AR was 0.05 μmol L−1. The new sensor was sensitive and stable for the detection of AR. Moreover, it was easily manufactured and very convenient for food samples such as soft and isotonic drinks as well as chili sauce.
- 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 datosElectochemical detection of imidacloprid using a screen printed single walled carbon nanotubes coated with and ionic liquids(International Journal of Electrochemical Sciences, 2018-05-10) River-Guzman, Karla; Franco, Lida Marcela; García-Beltrán, Olimpo; Calderón, Jorge A.; Nagles, EdgarThe simple modification of a screen printed single walled carbon nanotubes with ionic liquid 1-butyl-3-metilimidazolium tetrafluorborate allowed the development of a fast and selective methodology to determine imidacloprid (IMI). The morphological and conductive characteristics of the modified surface were analyzed with scanning electron microscopy and electrochemical impedance spectroscopy. The modified surface showed great activity towards the reduction of IMI to -1.2 V. The analytical variables were optimized using linear sweep voltammetry at 0.1 V for 60s, obtaining a limit of detection of 0.21 mg L-1(0.82 μmol L-1). Relative standard deviation with six different electrodes was of 2.6 % (n = 5). Finally, the potential interferers were studied and the sensor was applied in the determination of IMI using samples of commercial honey with recovery between 88.0 and 105.0 % for IMI.
- PublicaciónSólo datosEvaluation of the usefulness of a novel electrochemical sensor in detecting uric acid and dopamine in the presence of ascorbic acid using a screen-printed carbon electrode modified with single walled carbon nanotubes and ionic liquids(Electrochimica Acta, 2017-11-18) Nagles, Edgar; García-Beltrán, Olimpo; Calderón, Jorge A.A novel sensor was developed in order to determine dopamine (DP) and uric acid (UA) by adsorptive voltammetry, using optimal amounts of single walled carbon nanotubes (SWCNT) dispersed in chitosan solution (cs) and deposited on a screen-printed carbon electrode (SPCE). The electrode surface (cs-SWCNT/SPCE) was treated with the ionic liquid (IL) 1 butyl-3-metilimidazolium tetrafluorborate (BMIMBP4). The electro-catalytic properties of the cs-SWCNT-IL/SPCE were studied with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrode surface was studied using scanning electron microscopy (SEM). Anodic peak currents for DP and UA with BMIMBP4 in the presence of ascorbic acid (AA) increased by 17.0 and 70.0% respectively. Optimal parameters were (pH 2.4; adsorption time; tADS 100s and adsorption potential; EADS -0.10 V). Anodic peak currents were proportional to the concentration between 0.5 and 5.0 μmol L−1 using standard solutions of PD and UA respectively, and 0.50–30.0 μmol L−1 for DP and 0.50–1000 μmol L−1 for UA with real samples. Detection limits were 0.16 μmol L−1 for DP and 0.17 μmol L−1 for UA. The sensor was used in the determination of AU and DP in human urine samples spiked with quantities of DP with recovery between 85 and 102% for DA and UA respectively.
- 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.
- PublicaciónSólo datosSensitive and Profitable Electrochemical Detection of Uric Acid in the Presence of Dopamine with a Novel Carbon Paste Electrode Decorated with a Copper(II) Complex(Electroanalysis, 2019-08-07) Tamayo, Lenka V.; Torres, Juan F.; Llanos‐Penagos, Johisner; Calderón, Jorge A.; Nagles, Edgar; García‐Beltrán, Olimpo; Hurtado, John J.A new microcomposite with copper(II) complex and carbon paste (CuC/CPE) was developed to determine the uric acid (UA) content in the presence of dopamine (DP) and was characterized via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and energy dispersive spectroscopy (EDS). The results showed high selectivity for UA compared with DP because the anodic peak currents for DP were near those of a CPE without Cuc and were considerably increased for UA. The UA and DP increases were 86.9 % and 14.3 %, respectively, according to CV and 96.6 % and 25.5 %, respectively, according to square wave voltammetry (SWV) with the CuC/CPE. Moreover, the anodic peak separation for UA and DP was 0.17 V. With optimal parameters (pH, 3.3; adsorption time(tADS), 30 s;adsorption potential (EADS), 0.10 V), the anodic peak currents for UA were proportional to concentrations between 1.6 and 14.4 μmol L−1 using standard solutions with UA concentrations ranging from 8.0–40.5 μmol L−1 and real samples. The UA detection limit was 0.13 μmol L−1. The new sensor was used to determine the UA contentin human urine samples, and the method was checked with a urine chemistry control from Bio‐Rad based on human urine spiked with quantities of UA and showed a recovery between 84 % and 106 % at concentrations below 10.0 μmol L−1.
- PublicaciónSólo datosSensitive and profitable Electrochemical Detenction of Uric Acid in the Presence of Dopamine with a Novel Carbon Paste Electrode Decorated with a Copper (II) Complex(Electroanalysis, 2019-07-07) Tamayo, Lenka V.; Torres, Juan F.; Llanos‐Penagos, Johisner; Calderón, Jorge A.; Nagles, Edgar; García‐Beltrán, Olimpo; Hurtado, John J.A new microcomposite with copper(II) complex and carbon paste (CuC/CPE) was developed to determine the uric acid (UA) content in the presence of dopamine (DP) and was characterized via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and energy dispersive spectroscopy (EDS). The results showed high selectivity for UA compared with DP because the anodic peak currents for DP were near those of a CPE without Cuc and were considerably increased for UA. The UA and DP increases were 86.9 % and 14.3 %, respectively, according to CV and 96.6 % and 25.5 %, respectively, according to square wave voltammetry (SWV) with the CuC/CPE. Moreover, the anodic peak separation for UA and DP was 0.17 V. With optimal parameters (pH, 3.3; adsorption time(tADS), 30 s;adsorption potential (EADS), 0.10 V), the anodic peak currents for UA were proportional to concentrations between 1.6 and 14.4 μmol L−1 using standard solutions with UA concentrations ranging from 8.0–40.5 μmol L−1 and real samples. The UA detection limit was 0.13 μmol L−1. The new sensor was used to determine the UA contentin human urine samples, and the method was checked with a urine chemistry control from Bio‐Rad based on human urine spiked with quantities of UA and showed a recovery between 84 % and 106 % at concentrations below 10.0 μmol L−1.
- PublicaciónSólo datosSimultaneous determination of tartrazine, sunset yellow and allura red in foods using a new cobalt-decorated carbon paste electrode(Journal of Electroanalytical Chemistry, 2019-10-06) Penagos-Llanos, Johisner; García-Beltrán, Olimpo; Calderón, Jorge A.; Hurtado-Murillo, John A.; Nagles, EdgarA simple, sensitive and economical sensor based on carbon paste decorated with a cobalt complex (CoC/CPE) was developed and applied to the simultaneous detection of pairs of synthetic dyes most commonly used in foods, which are tartrazine-sunset yellow (TZ-SY) and tartrazine-allurared (TZ-AR). Micro composite surfaces were characterized by electrochemical impedance spectroscopy (EIS). Anodic peak currents for TZ-SY and TZ-AR as a function of pH, CoC concentration, time and adsorption potential were observed at 1.0–0.79 V and 1.0–0.81 V, respectively, by CV. In addition, the increase in the anodic peak currents was greater than 100% for TZ-SY and TZ-AR using the carbon paste decorated with the Co(II) complex. The detection limits were 0.30 × 10−6 - 0.90 × 10−6 mol L−1 for the TZ-SY pair and 0.8 × 10−7-0.37 × 10−6 mol L−1 for the TZ-AR pair. The new method was validated with a standard of unflavored gelatin spiked with small amounts of TZ-SY and TZ-AR and showed a recovery percentage greater than 90%. Finally, the versatility of the sensor was applied in foods such as orange and strawberry flavored gelatin, powdered, soft drinks and pharmaceutical dosages. The statistical study showed that this method is equally reproducible, stable and accurate compared to other previously reported methods.
- PublicaciónSólo datosVoltammetric determination of amaranth and tartrazine with a new double-stranded copper(I) helicate-single-walled carbon nanotube modified screen printed electrode(Journal of Electroanalytical Chemistry, 2018-05-26) Nuñez-Dallos, Nelson; Macías, Mario; García-Beltrán, Olimpo; Calderón, Jorge A.; Nagles, Edgar; Hurtado, JohnIn this work, we report the synthesis of a new double-stranded copper(I) helicate (H) and its use for the first time in a single-walled carbon nanotube-modified screen printed electrode (SWCNT/SPCE) for the voltammetric determination of amaranth (AM) and tartrazine (TZ). H was synthesized through a self-assembly process between Cu(I) iodide and 1,3-bis(1H-benzotriazol-1-ylcarbonyl)benzene (L). The compound was structurally characterized by infrared, photoluminescence spectroscopy, elemental and thermogravimetric analyses as well as single-crystal and powder X-ray diffraction. The SWCNT/SPCE was coated with H by simple drop casting, and the surface (H-SWCNT/SPCE) was characterized using cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and Raman spectroscopy. The presence of H on the surface of the modified electrode reduces the charge transfer resistance of the redox couple and improves the sensitivity toward the oxidation of AM and TZ with oxidation current increases of almost 80% and 60%, respectively, thus allowing their determination using square-wave adsorptive stripping voltammetry (SWAdSV). The detection limits (3σ/b) were 30.0 and 60.0 nmol L−1 for AM and TZ, respectively. The relative standard derivation was 3.5% (n = 7) with three different electrodes. Furthermore, the new sensor was applied in the detection of these dyes in commercial samples such as synthetic orange juice and a soft drink.
- PublicaciónSólo datosVoltammetric determination of thiomersal with a new modified electrode based on a carbon paste electrode decorated with La2O3(Journal of Electroanalytical Chemistry, 2019-01-15) Penagos Llanos, Johisner; Calderón, Jorge A.; Nagles, Edgar; Hurtado, Jhon J.A carbon-paste modified electrode decorated with La2O3 (LaOx/CPE) is reported for the first time for the voltammetric determination of thiomersal (THM) content. The LaOx/CPE surface was characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The presence of La2O3 on the surface of the carbon paste reduces the charge transfer resistance and improves the sensitivity toward the oxidation of THM, with an oxidation current increase of almost 60% and allows its determination by square-wave stripping voltammetry (SWSV). The detection limit (3σ/b) was 0.09 μmol L−1 and the relative standard deviation was 2.5% (n = 7) with three different electrodes. Furthermore, the new sensor was applied in the detection of THM in vaccines and pharmaceutical dosages.