Synthesis and Characterization of a Silicon Oxide Film Solid-Phase Extraction System for Lead Traces Determination. An All the Way Green Analytical Method.

COPELLO G; VIVOT ROCIO; VARELA FLORENCIA; L. E. DIAZ

INTERNATIONAL JOURNAL OF ENVIRONMENTAL ANALYTICAL CHEMISTRY

TAYLOR & FRANCIS LTD

Año: 2009

0306-7319

In this work an all the way green analytical procedure based on a silicon oxide film-solid phase extraction system is proposed for lead traces determination. From the synthesis of a solid phase extraction (SPE) system and throughout metal preconcentration and determination only aqueous media were employed. Characterization of the film was carried out by Scanning Electron Microscopy and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy. Preconcentration conditions, prior to Pb(II) Electrothermal Atomic Absorption Spectroscopy (ETAAS) determination, such as adsorption and desorption time, pH and temperature, were optimized. Langmuir, Freundlich and Dubinin-Radushkevich isotherm models were analyzed along with the evaluation of adsorption energy and standard free energy (ΔG0). The greatest adsorption was obtained with incubation at pH 7 at 37 ºC. By using a small volume of 0.5mol L-1 HNO3 (0.5 mL) lead was desorbed from the silicon oxide film after 2 h incubation, generating low amount of waste. The films showed better adjustment for the Langmuir model (R2=0.989). The detection limit (3.29σ) for Pb(II) was 0.228 µg L-1. The developed procedure is 10-fold more sensitive in comparison to direct ETAAS determination. Recovery values from soft tap-water and soft well-water were above 95%. When hard water was analyzed, Pb(II) adsorption was found to be interfered by Mg2+ and Ca2+. After five preconcentration cycles relative recovery was found not to decay below 90%, indicating that the silicon oxide film could be used for multiple lead determinations.