Examinando por Autor "Hurtado, John"
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- PublicaciónSólo datosAdsorptive stripping voltammetric determination of lead and cadmium in natural waters in the presence of rutin using a Nafion-mercury coated film electrode(International Journal of Electrochemical Science, 2018-05-08) Arancibia, Verónica; Nagles, Edgar; García-Beltrán, Olimpo; Hurtado, JohnA sensitive method for the simultaneous determination of Pb(II) and Cd(II) based on the formation of their complexes with rutin (RUT) and subsequent adsorptive deposition on a Nafion-mercury coated glassy carbon electrode (GC-NHgFE) is presented. The effects of various operational parameters such as pH, ligand concentration, accumulation potential, and time were optimized. The best experimental conditions found were: pH 3.5; CRUT: 0.10 mmol L-1; tads: 100 s, and Eads: 0.15 V. Under these conditions, the reductions signals of Pb-RUT and Cd-RUT complexes are found at -0.29 V and -0.46 V, respectively, while no signal of free RUT was seen. The relationship between peak current and Pb(II), Cd(II) concentrations are linear in the 1.0-62.0 μg L-1 range. The detection limits (DLs) were found to be 0.16 and 0.06 μg L-1 for Pb(II) and Cd(II), respectively. Finally, the method was applied to the determination of Pb(II) and Cd(II) in water from the Ambala river (Colombia) and in commercial mineral water with satisfactory results.
- PublicaciónSólo datosAdsorptive Stripping Voltammetric Determination of Lead and Cadmium in Natural Waters in the Presence of Rutin Using a Nafion–Mercury Coated Film Electrode(ESG, 2018-08-05) Arancibia, Verónica; Nagles, Edgar; García-Beltrán, Olimpo; Hurtado, JohnA sensitive method for the simultaneous determination of Pb(II) and Cd(II) based on the formation of their complexes with rutin (RUT) and subsequent adsorptive deposition on a Nafion–mercury coated glassy carbon electrode (GC-NHgFE) is presented. The effects of various operational parameters such as pH, ligand concentration, accumulation potential, and time were optimized. The best experimental conditions found were: pH 3.5; CRUT: 0.10 mmol L–1; tads: 100 s, and Eads: 0.15 V. Under these conditions, the reductions signals of Pb–RUT and Cd–RUT complexes are found at –0.29 V and –0.46 V, respectively, while no signal of free RUT was seen. The relationship between peak current and Pb(II), Cd(II) concentrations are linear in the 1.0–62.0 µg L–1 range. The detection limits (DLs) were found to be 0.16 and 0.06 μg L−1 for Pb(II) and Cd(II), respectively. Finally, the method was applied to the determination of Pb(II) and Cd(II) in water from the Ambala river (Colombia) and in commercial mineral water with satisfactory results.
- PublicaciónSólo datosAdsorptive Stripping Voltammetric Determination of Morin in Tea Infusions and Chocolate Drinks on a Gold Electrode. Effect of Cetylpyridinium Bromide on the Sensitivity of the Method(International Journal of Electrochemical Sciences, 2017-09-12) Arancibia, Verónica; García-Beltrán, Olimpo; Hurtado, John; Nagles, EdgarThe use of a gold electrode to determine Morin (MO) in the presence of two polyphenolic compounds as Quercetin (Q) and Rutin (RU) by cyclic and adsorptive stripping voltammetry is reported. The effects of various operational parameters such as pH, supporting electrolyte, adsorptive potential and time (Eads, tads) were optimized. The optimum experimental conditions chosen were: pH 3.0 (phosphate buffer 0,001 mol L-1 ), Eads:−0.20 V and tads: 60s. Under these conditions MO was oxidized at +0.49 V and the linear calibration curves ranged from 0.5 and 5.6 μmol L–1 . When cetylpyridinium bromide (CPB) was added to the electrochemical cell, a Morin/CPB aggregate was formed, increasing the peak current of MO for at least 30 % than in the absence of this cationic surfactant, and the detection limit changed from 0.40 to 0.083 μmol L-1 with 15.0 mol L-1 of CPB. The method was validated determining MO in two water samples spiked with MO, Q and RU and finally, was successfully applied to the determination of MO in tea infusions and chocolate drinks samples.
- PublicaciónSólo datosDetermination of Rutin in Drinks Using an Electrode Modified with Carbon Nanotubes-Prussian Blue(Journal of Analytical Chemistry, 2018-05-02) Nagles, Edgar; Penagos-Llanos, Johisner; García-Beltrán, Olimpo; Hurtado, JohnA new sensor was developed using a screen-printed carbon electrode modified with single-walled carbon nanotubes (SWCNTs) and Prussian blue (PB) coated with chitosan. The modified electrode allowed the oxidation and reduction of rutin at 0.25 and 0.096 V, respectively, with a ΔE of 0.154 V. Furthermore, the peak currents increase nearly 100% compared with the electrode without modification. The process was more reversible compared with the electrode modified with only SWCNTs or PB. Cyclic voltammetry was used to characterize the modified electrode surface. The quantification of rutin was more sensitive with adsorptive stripping voltammetry than with anodic stripping voltammetry. Adsorption potential, adsorption time and pH were optimized based on the oxidation of rutin: Eads =–0.10 V, tads = 60 s, pH 3.0. The detection limit (3σ/b) was 0.01 μM and the relative standard derivation was 3%. The new sensor was used in the quantification of rutin in black tea, coffee and synthetic drink of tea with satisfactory results.
- PublicaciónSólo datosDevelopment of a microcomposite with single-walled carbon nanotubes and Nd2O3 for determination of paracetamol in pharmaceutical dosage by adsorptive voltammetry(Journal of Pharmaceutical Analysis, 2018-11-22) García-Beltrán, Olimpo; Nagles, Edgar; Penagos-Llanos, Johisner; Arancibia, Verónica; Hurtado, JohnThis study presents for the first time a new composite of carbon paste (CP), single-walled carbon nanotubes (SWCNTs) and Nd2O3 (NdOX). This versatile composite (NdOX-SWCNT/CPE) was applied to the oxidation of paracetamol (PCM). The newly formed surface was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results showed greater conductivity and a higher surface area for the composite than those of the carbon paste alone. Moreover, the anodic peak currents for PCM increased from 1.6 to 3.6 µA with CPE and NdOX-SWCNT/CPE, indicating an increase of nearly 51.0% for the anodic peak current. On the other hand, the anodic peak potentials shifted from 0.67 to 0.57 V. The detection limits were 0.05 µmol/L with NdOX-SWCNT/CPE and 0.50 µmol/L with SWCNT/CPE. The relative standard deviations (RSDs) were 1.5% (n = 7). The accuracy and interference of the methods were evaluated with a urine chemistry control spiked with known quantities of PCM, uric acid, dopamine, ascorbic acid, caffeine, acetylsalicylic acid, tartrazine, sunset yellow, allure red, rutin, morin and metal ions. Finally, the novelty and usefulness of the composite were evaluated to quantify PCM in pharmaceutical dosage forms such as tablets, powders and syrups for children.
- PublicaciónSólo datosDevelopment of a Novel Electrochemical Sensor Based on a Carbon Paste Electrode Decorated with Nd2O3 for the Simultaneous Detection of Tartrazine and Sunset Yellow(Electroanalysis, 2018-09-21) Marquez‐Mariño, Karen; Penagos-Llanos, Johisner; García-Beltrán, Olimpo; Nagles, Edgar; Hurtado, JohnThe simultaneous detection of tartrazine (TZ) and sunset yellow (SY) using a carbon paste‐decorated neodymium (III) oxide electrode (NdOx/CPE) is reported for the first time in this work. The surface properties of the NdOx/CPE were studied by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. The anodic peak currents for TZ and SY increased by more than 60 %, and the anodic peak potentials for TZ and SY were observed at potential values less positive than those of the carbon paste without NdOX. Under the optimal parameters (pH 3.0; accumulation time tACC 30 s; and accumulation potential EACC 0.10 V), the detection limits for TZ and SY observation were 0.02 μmol L−1 (10.6 μg L−1) and 0.09 μmol L−1 (40.6 μg L−1), respectively. The new sensor was sensitive, stable, easily manufactured, and very convenient for the detection of TZ and SY in food samples and pharmaceutical materials and provided consistent results.
- PublicaciónSólo datosDevelopment of a novel electrochemical sensor based on cobalt(II) complex useful in the detection of dopamine in presence of ascorbic acid and uric acid(Journal of Electroanalytical Chemistry, 2017-02-01) Nagles, Edgar; Ibarra, Laura; Penagos-Llanos, Johisner; Hurtado, John; García-Beltrán, Olimpo[(Co(bdmpzm)2(NCS)2] (bdmpzm = bis(3,5-dimethylpyrazol-1-yl)methane) was synthesized and combined with single walled carbon nanotubes (SWCNT) and nafion on a screen printed carbon electrode (SPCE). The electrocatalytic activity of modified electrode (Nafion-SWCNT-[Co(bdmpzm)2(NCS)2]/SPCE) was evaluated for dopamine (DA) oxidation. Anodic and cathodic peak were seen to 0.42 V.and0.29 V respectively, showed a much more quasi-reversible process, (∆ V 0.128) compared with the electrode without cobalt complex. The detection limit (3σ/b) for dopamine was 0.095 μmol L− 1. The studies of reproducibility determined as relative standard deviation (RSD) was 2.5%.(n = 5) with four different electrodes. The repeatability were 1.5% (n = 5) The new sensor was used in the quantify DA in human urine with an average recovery between 83.0 and 93.0%.
- PublicaciónSólo datosDevelopment of Antibacterial and Antifungal Triazole Chromium(III) and Cobalt(II) Complexes: Synthesis and Biological Activity Evaluations(NCBI, 2018-08-13) Nagles, Edgar; Murcia, Ricardo A.; Leal, Sandra M.; Roa, Martha V.; Muñoz-Castro, Alvaro; Hurtado, JohnIn this work, six complexes (2⁻7) of Cr(III) and Co(II) transition metals with triazole ligands were synthesized and characterized. In addition, a new ligand, 3,5-bis(1,2,4-triazol-1-ylmethyl)toluene (1), was synthesized and full characterized. The complexes were obtained as air-stable solids and characterized by melting point, electrical conductivity, thermogravimetric analysis, and Raman, infrared and ultraviolet/visible spectroscopy. The analyses and spectral data showed that complexes 3⁻7 had 1:1 (M:L) stoichiometries and octahedral geometries, while 2 had a 1:2 (M:L) ratio, which was supported by DFT calculations. The complexes and their respective ligands were evaluated against bacterial and fungal strains with clinical relevance. All the complexes showed higher antibacterial and antifungal activities than the free ligands. The complexes were more active against fungi than against bacteria. The activities of the chromium complexes against Candida tropicalis are of great interest, as they showed minimum inhibitory concentration 50 (MIC50) values between 7.8 and 15.6 μg mL-1. Complexes 5 and 6 showed little effect on Vero cells, indicating that they are not cytotoxic. These results can provide an important platform for the design of new compounds with antibacterial and antifungal activities.
- PublicaciónSólo datosElectrochemical sensors for dopamine using graphene-cobalt(II) complex modified glassy carbon electrode by adsorptive voltammetry(Analytical and Bioanalytical Electrochemistry, 2016-11-15) Cuadrado, Carol; Ibarra, Laura; Hurtado, John; García-Beltrán, Olimpo; Nagles, Edgar[Co(bdmpzm)2(NCS)2] (bdmpzm=bis(3,5-dimethylpyrazol-1-yl)methane) was dispersed in graphene oxide (GOx). Composite GOx-[Co(bdmpzm)2(NCS)2] was deposited on a glassy carbon electrode (GCE) and reduced at -1.0 by 60 s. The modified electrode rGOx-[Co(bdmpzm)2(NCS)2]/GCE allowed the oxidation for dopamine (DA) at 0.41 V Our results showed reversible and sensitive process, (∆V 0.09 V) compared with the electrode without modified in buffer phosphate solution pH 3.0. The detection limit (3σ/b) for dopamine was 0.11 µmol L-1 and the RSD was 3.0%. The presence of uric acid and ascorbic acid did not interfere with the signal for dopamine.
- PublicaciónSólo datosElectrocomposite developed with chitosan and ionic liquids using screen-printed carbon electrodes useful to detect rutin in tropical fruits(Sensors, 2018-08-30) Muñoz, Lili; Arancibia, Verónica; García-Beltrán, Olimpo; Nagles, Edgar; Hurtado, JohnThis work reports the development of a composite of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BP4) and chitosan (CS) described in previous reports through a new method using cyclic voltammetry with 10 cycles at a scan rate of 50.0 mV s−1. This method is different from usual methods such as casting, deposition, and constant potential, and it allows the development of an electroactive surface toward the oxidation of rutin by stripping voltammetry applied to the detection in tropical fruits such as orange, lemon, and agraz (Vaccinium meridionale Swartz), with results similar to those reported in previous studies. In addition, the surface was characterized by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and Raman spectroscopy. The limit of detection was 0.07 µmol L−1 and the relative standard deviation (RSD) of 10 measurements using the same modified electrode was 0.86%. Moreover, the stability of the sensor was studied for six days using the same modified electrode, where the variation of the signal using a known concentration of rutin (RT) was found to be less than 5.0%. The method was validated using a urine chemistry control spiked with known amounts of RT and possible interference was studied using ten substances including organic and biological compounds, metal ions, and dyes. The results obtained in this study demonstrated that this electrodeveloped composite was sensitive, selective, and stable. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.
- PublicaciónSólo datosEx situ poly(3,4-ethylenedioxythiophene)-sodium dodecyl sulfate-antimony film electrode for anodic stripping voltammetry determination of lead and cadmium(International Journal of Electrochemical Sciences, 2016-08-15) Nagles, Edgar; García-Beltrán, Olimpo; Hurtado, JohnA poly(3,4-ethylenedioxythiophene)-sodium dodecyl sulfate coated antimony film electrode PEDOTSDS-SbFE was prepared ex situ and applied to determine Pb(II) and Cd(II) by anodic stripping voltammetry (ASV). The PEDOT-SDS-SbFE exhibited well developed signals for the oxidation of Pb and Cd at -0.12 and -0.40 V respectively, with higher current compared to unmodified electrodes. The optimum parameters for PEDOT-SDS-SbFE preparation consisted in an EDOT 0.01 mol L -1 in KCl 0.1 mol L -1 with SDS 1.0 x 10 -3 mol L -1 solution at scanning rate of 50 mVs -1 (10 cycles -0.1 a 1.6 V), 200 mg L -1 Sb(III) in 0.5 mol L -1 HCl at -1.2 V (150 s) and for the determination of Pb(II) and Cd(II) were pH = 4.0 (acetate buffer); Eacc = -1.0 V and tacc = 60 s. The electrode showed good linear behavior in concentration range from 4.5 to 140.0 μg L -1 for both metal ions. The limit of detection (3s) was 0.50 and 0.80 μg L -1 for Pb(II) and Cd(II) respectively. The RSD for a Pb(II) a Cd(II) 47.0 μg L -1 was 1.5% for seven successive assays. The method was validated using model solutions with satisfactory results. The method was applied to the determination of Pb(II) and Cd(II) in commercial mineral water and river water samples.
- PublicaciónSólo datosIn situ-Mercury Film Electrode for Simultaneous Determination of Lead and Cadmium Using Nafion Coated New Coumarin Schiff Base as Chelating-Adsorbent(International Journal of Electrochemical Sciences, 2016-11-10) Nuñez-Dallos, Nelson; Cuadrado, Carol; Hurtado, John; Nagles, Edgar; García-Beltrán, OlimpoReaction of o-phenylenediamine and 8-formyl-7-hydroxycoumarin yield a new coumarin salen ligand, (CSB) which was isolated as orange air-stable solid and characterized by melting point, thermogravimetric analysis (TGA), mass spectra, infrared and NMR (1H, 13C) spectroscopy. New CSB was dispersed in nafion and nafion-CSB composite was deposited on a glassy carbon electrode. The modified electrode nafion-CSB/GCE allowed the formation in-situ of mercury film for detection of Pb (II) and Cd(II) by anodic stripping voltammetry (ASV) in buffer phosphate solution pH 3.0 and 4.0. Optimal conditions were studied (mercury concentration: CHg 40.0 mg L-1 ; CSB concentración; CCSB; 20.0 µmol L-1 ; pH 3.0 and pH 4.0; EACC:-1.1 V and tACC: 80).The detection limit (3σ/b) for Pb (II) Cd (II) were of 0.15 µg L–1 for Pb(II) and Cd(II) at pH 3.0. Moreover, 0.071 and 0.080 µg L–1 for Pb(II) and Cd(II), respectively at pH 4.0, The method was validated using ICP multi-element standard solution IX (Merck) containing As, Be, Cd, Cr(VI), Hg, Ni, Pb, Se and Tl 100 mg L-1 . Finally, river, tap and mineral waters were analyzed.
- PublicaciónSólo datosSimultaneous Determination of Lead and Cadmium by Stripping Voltammetry Using in-situ Mercury Film Glassy Carbon Electrode Coated with Nafion-Macrocyclic Ester(International Journal of Electrochemical Sciences, 2017-07-12) Lara, Jesid; Torres, Juan F.; García-Beltrán, Olimpo; Nagles, Edgar; Hurtado, JohnThis work report a sensitive and selective anodic stripping method for the simultaneous determination of Pb(II) and Cd(II) using (3,10,18,25-tetraoxapentacyclo [25.3.1.112,16.04,9.0 19,24] dotriaconta1(31),4(9),5,7,12(32),13,15,19,21,23,27,29-dodecaene-2,11,17,26-tetrone) macrocyclic ester (L). Anodic peak currents were increased from 1.16 to 31.48 µA for Pb(II) and 0.22 to 6.68 µA for Cd(II) when the in-situ mercury film electrode was modified with nafion and (L). Moreover, potentials separation values for Cd-Pb shift from 150 to 190 mV. Optimal parameters such as: pH; L concentration (CL), mercury concentration (CHg), accumulation potential (EACC) and accumulation time (tACC) were pH 4.0 for Pb(II) and 5.0 for Cd(II) using phosphate buffer solution (PBS), CL 12.0 mmol L -1 , CHg 28.0 mg L-1 , EACC -1.0 V and tACC 60. Detection limits (DoL) were 0.085 and 0.80 µg L-1 for Pb(II) and Cd(II) respectively. The relative standard deviation (RSD) for seven measurements of Pb(II) and Cd(II) 9.0 µg L-1 were of 2.5 and 2.0% respectively. The method was validated by ICP multielement standard solution IX (Merck) containing As, Be, Cd, Cr(VI), Hg, Ni, Pb, Se and Tl 100 mg L1 . Finally, useful of the modified electrode was developed in the analysis of Pb(II) and Cd(II) using tap water samples
- PublicaciónSólo datosSpeciation of morin and rutin in black tea, Cymbopogon citratus and fruit infusions by adsorption voltammetry using screen-printed carbon electrodes coated with chitosan: effect of pH on speciation(Analytical Methods, 2018-07-26) Nagles, Edgar; García-Beltrán, Olimpo; Hurtado, JohnThis paper presents the versatility of chitosan in the preparation of modified electrodes without the use of other substances. We present a sensitive and selective method of speciation for the determination of rutin (RT) and morin (MR) in natural products on a screen-printed carbon electrode coated with chitosan (CS-SPC). MR and RT may be adsorbed onto the surface of the SPC electrode coated with CS, increasing the intensity of the current by more than 60 and 45% for RT and MR, respectively, compared to that of the unmodified SPC. On the other hand, anodic peak currents were observed at the same potential value. This effect can impede the speciation for the detection of RT and MR in real samples. By evaluating the concentration of CS deposited on the electrode surface, a separation of 100 mV between RT and MR was achieved. Moreover, anodic peak currents for RT and MR as a function of the pH using a phosphate buffer solution (PBS) were evaluated, and the results clearly showed that in an acid medium, the MR signal is only 8.0% compared to that of the RT signal. These two parameters make speciation possible for the detection and quantification of RT and MR. Detection limits were 0.090 and 0.90 μmol L-1 for RT and MR, respectively. The relative standard derivations (RSD) were 3.5 and 4.0%, respectively. The accuracy was evaluated using a urine chemistry control spiked with known quantities of RT and MR. Finally, the usefulness of the modified electrode was evaluated to quantify RT and MR in commercial samples of black tea, as well as infusions of Cymbopogon citratus and fruits, which provided consistent results compared to previous reports.
- PublicaciónSólo datosSynthesis and structural characterization of new macrocyclic ester. study as an immobilization agent for determination of lead by anodic stripping voltammetry(International Journal of Electrochemical Science, 2017-03-12) Torres, Juan F.; Reiber, Andreas; Macías, Mario; García-Beltrán, Olimpo; Nagles, Edgar; Hurtado, JohnNew macrocyclic ester (L) was yielded through reaction of catechol with isophthaloylchloride and isolated as white solid, air stable at room temperature. L was characterized by melting point, mass spectra, FTIR and NMR ( 1 H, 13 C) spectroscopy. The molecular structure was determined by single-crystal X-ray diffraction. The macrocyclic compound was evaluated to determine ultra-trace concentrations of Pb (II) by anodic stripping voltammetry in the presence of Cd(II). The method is based on the formation of a complex between lead and the macrocyclic ester, immobilized on a vitreous carbon electrode, allowing the oxidation of lead by voltammetric scan, using square wave modulation method. Anodic peak current was observed at -0.20 V for Pb(II). Under the best experimental conditions (pH 4.0; L concentration 10.0 mmol L -1 ; accumulative potential (Eacc) -0.8 V and accumulative time (tacc) of 60 s) anodic peak current was proportional to the Pb (II) concentration up to 80.0 μg L -1 , with a detection limit (3σ) of 0.33 μg L -1 . The proposed method was validated by determining Pb(II) in model solution with ultra-pure water with satisfactory results.
- PublicaciónSólo datosSynthesis, crystal structure, catalytic and anti-Trypanosoma cruzi activity of a new chromium(III) complex containing bis(3,5-dimethylpyrazol-1-yl)methane(Journal of Molecular Structure, 2017-06-01) Hurtado, John; Ibarra, Laura; Yepes, David; García-Huertas, Paola; Macías, Mario; Triana-Chavez, Omar; Nagles, Edgar; Suescun, Leopoldo; Muñoz-Castro, AlvaroThe reaction of CrCl36H2O with the ligand bis(3,5-dimethylpyrazol-1-yl)methane (L) yielded the cationic complex [(Cr(L)(H2O)2Cl2]+, which crystallized as the chloride trihydrate [(Cr(L)(H2O)2Cl2]Cl·3H2O. The chromium complex was characterized by elemental analysis, electrical conductivity, Infrared and Ultraviolet/Visible spectroscopy. The crystal structure determination using single-crystal X-ray diffraction showed a chromium center in a distorted octahedral coordination sphere. In the crystal, the packing was directed by OH⋯(O,Cl) hydrogen bonds and weak CH⋯O interactions to build a monoclinic P21/c supramolecular structure. The complex showed excellent properties as an initiator for the ring opening polymerization of є-caprolactone (CL) under solvent-free conditions. The obtained polymer showed high crystallinity (89.9%) and a decomposition temperature above 475 °C. In addition, the new complex was evaluated against epimastigotes from Trypanosoma cruzi (T. cruzi) strains. The results indicated that this complex has a high activity against this parasite with a minimum inhibitory concentration 50 (MIC50) of 1.08 μg/mL. Interestingly, this compound showed little effect on erythrocytes, indicating that it is not cytotoxic. These results provide interesting contributions to the design of metal complexes by using simple and accessible ligands with activity against T. cruzi and with potential applications in the polymerization of CL.
- PublicaciónSólo datosSynthesis, crystal structure, catalytic and anti-Trypanosoma cruzi activity of a new chromium(III) complex containing bis(3,5-dimethylpyrazol-1-yl)methane(Journal of Molecular Structure, 2017-06-01) Hurtado, John; Ibarra, Laura; Yepes, David; García-Huertas, Paola; Macías, Mario A.; Triana-Chavez, Omar; Nagles, Edgar; Suescun, Leopoldo; Muñoz-Castro, AlvaroThe reaction of CrCl36H2O with the ligand bis(3,5-dimethylpyrazol-1-yl)methane (L) yielded the cationic complex [(Cr(L)(H2O)2Cl2]+, which crystallized as the chloride trihydrate [(Cr(L)(H2O)2Cl2]Cl·3H2O. The chromium complex was characterized by elemental analysis, electrical conductivity, Infrared and Ultraviolet/Visible spectroscopy. The crystal structure determination using single-crystal X-ray diffraction showed a chromium center in a distorted octahedral coordination sphere. In the crystal, the packing was directed by Osingle bondH⋯(O,Cl) hydrogen bonds and weak Csingle bondH⋯O interactions to build a monoclinic P21/c supramolecular structure. The complex showed excellent properties as an initiator for the ring opening polymerization of є-caprolactone (CL) under solvent-free conditions. The obtained polymer showed high crystallinity (89.9%) and a decomposition temperature above 475 °C. In addition, the new complex was evaluated against epimastigotes from Trypanosoma cruzi (T. cruzi) strains. The results indicated that this complex has a high activity against this parasite with a minimum inhibitory concentration 50 (MIC50) of 1.08 μg/mL. Interestingly, this compound showed little effect on erythrocytes, indicating that it is not cytotoxic. These results provide interesting contributions to the design of metal complexes by using simple and accessible ligands with activity against T. cruzi and with potential applications in the polymerization of CL.
- 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.