Synthesis and characterisation of a silicon oxide film solid-phase extraction system for lead traces determination: An all the way green analytical method

G. J. COPELLO; R. MARTÍNEZ VIVOT; F. VARELA; L. E. DÍAZ

INTERNATIONAL JOURNAL OF ENVIRONMENTAL ANALYTICAL CHEMISTRY

TAYLOR & FRANCIS LTD

Año: 2010 p. 1 - 16

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 the metal preconcentration and determination only aqueous media were employed. Characterisation 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 AbsorptionSpectrometry (ETAAS) determination, such as adsorption and desorption time, pH and temperature, were optimised. Langmuir, Freundlich 20 and Dubinin-Radushkevich isotherm models were analyzed along with the evaluation of adsorption energy and standard free energy (DG0). The greatest adsorption was obtained with incubation at pH 7 and 37C. By using a small volume of 0.5 mol L1 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 (R2¼0.989). The detection limit (3.29) for Pb(II) was 0.228 mgL1. 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 30 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.