Search

espanolEn este trabajo, se estudio la transferencia de los herbicidas ametrina, atrazina y prometrina a traves de la interfase de dos soluciones electroliticas inmiscibles (agual 1,2-dicloroetano) mediante las tecnicas de voltamperometria ciclica y cronoamperometria en una celda electroquimica de vidrio de cuatro electrodos. Los experimentos se llevaron a cabo en condiciones acidas para asegurar la protonacion de la molecula, a traves de los voltamperogramas ciclicos se determino el potencial de transferencia para cada una de las triazinas estudiadas, mismo que sirvio para realizar los estudios cronoamperometricos. Estos ultimos mostraron valores de coeficientes de difusion del orden de 10-6 cm2 s-1, los cuales estan dentro de los parametros obtenidos por voltamperometria ciclica. Los resultados sugieren que las triazinas se mueven mas rapido en la fase acuosa que en la fase organica. Asi, desde un punto de vista ambiental, estos resultados ayudan a comprender el transporte de este tipo de compuestos a traves de un sistema bifasico, como lo es la membrana-agua de una celula biologica. EnglishIn this work, the transfer of ametryn, prometryn and atrazine herbicides was studied through the interface of two immiscible electrolyte solutions (water 1,2-dichloroethane) using cyclic voltammetry and chronoamperometry techniques in a four electrode configuration cell. The experiments were carried out under acidic conditions to ensure protonation of the molecule and the formal transfer potential for the three herbicides was measured. The chronoamperometric results showed that diffusion coefficients values are in order of 10-6 cm2 s-1, which are within the parameters obtained by cyclic voltammetry. The results suggest that the triazines move faster in the aqueous phase than in the organic phase. Thus, from an environmental point of view, these results could help to understand the transport of these compounds through a two-phase system, such as the membrane water from a biological cell.

The quantification of lead in water samples is presented at the sub-ppb level through preconcentration with cloud point extraction (using Triton x-100 and eriochrome black T) and atomic absorption spectrometry with electrothermal atomization. In order to study the influence of several variables, experimental design analyses were carried out. Linearity was observed between 0.15 to 1.20 ng mL−1 (r = 0.98), with a detection limit of 0.04 ng mL−1 and a quantification limit of 0.15 ng mL−1. A mean recovery of 90 ± 9% (n = 6, P = 0.05) was found; at the precision was 9% expressed as the coefficient of variation. Anions and cations that were studied did not affect the recovery of lead. Water samples of different sources were analyzed directly as well as by the standard addition method; no statistical differences were found between the two procedures. Finally, the present methodology was compared with liquid–liquid extraction of the lead-ditizone complex, using green analytical indicators proposed for this purpose.