Electrochemical behavior of simetryn herbicide at water|1,2-dichloroethane interface

Herein, the electrochemical behavior of the simetryn herbicide at the water|1,2-dichloroethane interface was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Parameters such as transfer Gibbs energy, ionic partition coefficient, and the apparent rate constants across the interface were evaluated. According to the results, the ionic form of this herbicide is highly hydrophobic because Δw o G0 SIMH w→o + is 3.57 kJ mol−1 and logPSIMH 0 + is −0.622. In addition, the ionic partition diagram for this compound shows dual behavior as a function of pH: when pH pKa, simetryn serves as a mobile proton carrier across the interface. The present study offers some important insights that help in understanding the partitioning and kinetic processes of environmentally important molecules across biological membranes.Fil: Velázquez-Manzanares, Miguel. Universidad Autonoma de Coahuila; MéxicoFil: García Martínez, Humberto. Universidad Autonoma de Coahuila; MéxicoFil: Yudi, Lidia Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Amador-Hernández, Judith. Universidad Autonoma de Coahuila; MéxicoFil: de la Garza Rodríguez, Iliana M.. Universidad Autonoma de Coahuila; MéxicoFil: Colunga Urbina, Edith M.. Universidad Autonoma de Coahuila; Méxic

Immobilization of Aspergillus niger lipase on chitosan-coated magnetic nanoparticles using two covalent-binding methods

Aspergillus niger lipase immobilization by covalent binding on chitosan-coated magnetic nanoparticles (CMNP), obtained by one-step co-precipitation, was studied. Hydroxyl and amino groups of support were activated using glycidol and glutaraldehyde, respectively. Fourier transform infrared spectrometry, high-resolution transmission electron microscopy and thermogravimetric analysis confirmed reaction of these coupling agents with the enzyme and achievement of a successful immobilization. The derivatives showed activities of 309.5 ± 2.0 and 266.2 ± 2.8 U (g support)(-1) for the CMNP treated with glutaraldehyde and with glycidol, respectively. Immobilization enhanced the enzyme stability against changes of pH and temperature, compared to free lipase. Furthermore, the kinetic parameters K m and V max were determined for the free and immobilized enzyme. K m value quantified for enzyme immobilized by means of glutaraldehyde was 1.7 times lowers than for free lipase. High storage stability during 50 days was observed in the immobilized derivatives. Finally, immobilized derivatives retained above 80% of their initial activity after 15 hydrolytic cycles. The immobilized enzyme can be applied in various biotechnological processes involving magnetic separation.Fil: Osuna, Yolanda. Universidad Autónoma de Coahuila; MéxicoFil: Sandoval, José. Universidad Autónoma de Coahuila; MéxicoFil: Saade, Hened. Centro de Investigación en Química Aplicada; MéxicoFil: López, Raúl G.. Centro de Investigación en Química Aplicada; MéxicoFil: Martinez, José L.. Universidad Autónoma de Coahuila; MéxicoFil: Colunga, Edith M.. Universidad Autónoma de Coahuila; MéxicoFil: de la Cruz, Gabriela. Universidad Autónoma de Coahuila; MéxicoFil: Segura, Elda P.. Universidad Autónoma de Coahuila; MéxicoFil: Arevalo, Fernando Javier. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zon, María Alicia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fernandez, Hector. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ilyina, Anna. Universidad Autónoma de Coahuila; Méxic

SEMI-CONTINUOUS DETERMINATION OF NO2 IN PASSIVE DIFFUSERS BY FLOW INJECTION/UV-VIS SPECTROPHOTOMETRY

In this work the development of a semi-automated method by flow injection for spectrophotometric indirect determination of NO2, is described. The gas of environmental importance is captured through passive diffusers built in the laboratory, where it undergoes a reaction with triethanolamine to form nitrite ions in relation 1:1, which are determined after the derivatization with sulfanilamide and N-(1-naphthyl) ethylenediamine. It’s concluded that the proposal method is quick and easy, as well as sensitive and selective to determine the chemical specie of interest. The estimated NO2 concentration in the air of Saltillo in Coahuila was 2.6 ± 0.3 mg m-3, which was above the maximum recommended by NOM-023-SSA1-1993 norm