CONICET | Buscador de Institutos y Recursos Humanos

Simposio; 16 Latin American Symposium on Biotechnology, Biomedical, Biopharmaceutical and Industrial Applications of Capillary Electrophoresis and Microchip Technology; 2010

Resumen:

OPEN-TUBE CAPILLARY ELECTROCHROMATOGRAPHY WITH C-MWNTS FOR THE DETECTION OF HEAVY METALS USING INDIRECT DETECTION Patricia W. Stege, Luis D. Martínez, José A. Gasquez, Lorena L. Sombra. INQUISAL, Chemical Institute of San Luis , National University of San Luis-CONICET. Chacabuco y Pedernera. D5700BWS. San Luis, Argentina. E-mail: pwstege@unsl.edu.ar A wide variety of heavy metals, pesticides, and chlorinated solvents have been detected in soil, water, and air. Since heavy metals are mobile and easily absorbed by plants in the environment, they could be transferred to the human body through nourishment. The bioaccumulation of high concentrations of heavy metals in plants tissues, such as Triticum spp. and Helianthus annuus L. species, can be detected in both leaves and roots [1]. Capillary electrochromatography (CEC) is a relatively new miniaturized separation technique that combines the advantages of the high speed and efficiency of CE with the high selectivity and increased sample loading of HPLC [2]. Because of their highly porous and hollow structure, large specific surface area, and light mass density, carboxylic multi-walled carbon nanotubes (c-MWNTs) have been investigated for the removal of organic pollutions, metal ions and some radionuclides as superior adsorbents. The incorporation of c-MWNTs as stationary phase resulted in the addition of nanoscale interactions that enhanced both resolution and sensibility of the separation. The c-MWNTs were successfully attached after the silanization of the inner surface of the capillary and were applied for the determination of Cu and Cd in leaves and roots of wheat and sunflower using UV indirect detection. This technique require the extraction of the metal from the biological samples, with this aim three digestion procedures were applied. The digestion procedures tested were: 1- batch using a mixture of HNO3+HCl, 2- microwave (MW)-assisted acid treatment with an acid mixture of HNO3+HCl, and 3- microwave (MW)-assisted acid treatment with H2O2. The samples obtained by the different procedures were injected into the CE for the following separation and detection of the metals. The detection was performed at 214 nm, and the applied voltage was 25 kV. The samples were pressure-injected at the cathodic side at 0.5 psi for 10 seconds and the background electrolyte (BGE) used consisted of 6 mM imidazole, pH 4.0. The best results were obtained with the digestion 3 of the plant material. The method showed linear response in the ranges of 0.02-5.00 ng/L (Cu) and 0.155.00 ng/L (Cd). The limits of detection were 12 pg/L for Cu and 53 pg/L for Cd. The proposed method allows the rapid determination of heavy metals in from both studied plants. It was recently demonstrated that MW-assisted acid treatment with H2O2 could be used satisfactorily for sample clean-up technique prior to CEC determination of various metals species. This is the first report of the draw on of c-MWNTs as a stationary phase in an open tube capillary electrochromatography for the separation of heavy metals. The resolution and sensibility was improved compared with the fused-silica capillary. [1]R.L. Chaney, Natl. Assoc. State Univ. Land Grant COIL, Washington DC, (1973), pp. 129-141. [2] Y. Huo,W.T. Kok, Electrophoresis 29 (2008) 80-93.