Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10560960 | Talanta | 2005 | 6 Pages |
Abstract
Square wave voltammetry automated by sequential injection analysis was applied to determine the Freundlich adsorption coefficients for the adsorption of atrazine onto a clay rich soil. The detection limit in soil extracts was between 0.18 and 0.48 μmol Lâ1, depending on the medium used to prepare the extracts (0.010 mol Lâ1 KCl, CaCl2 or HNO3 and 0.0050 mol Lâ1 H2SO4), all of them conditioned in 40 mmol Lâ1 Britton-Robinson buffer at pH 2.0 in presence of 0.25 mol Lâ1 NaNO3. Also in soil extracts the linear dynamic range was between 1.16 and 18.5 μmol Lâ1 (0.25-4.0 μg mLâ1), with a sampling frequency of 190 hâ1. The Kf Freundlich adsorption coefficient was 3.8 ± 0.2 μmol1â1/n Ln kgâ1 in medium of 0.010 mol Lâ1 KCl or CaCl2, but increased to 7.7 ± 0.1 and 9.0 ± 0.3 μmol1â1/n Ln kgâ1 in 0.010 mol Lâ1 HNO3 and 0.0050 mol Lâ1 H2SO4, respectively. The increase of Kf was related to the decrease of pH from 6.4-6.7 in KCl and CaCl2 to 3.7-4.0 in presence of HNO3 or H2SO4, which favors protonation of atrazine, facilitating electrostatic attractions with negative charges of the clay components of the soil. The 1/n parameters were between 0.76 and 0.86, indicating that the isotherms are not linear, suggesting the occurrence of chemisorption at specific adsorption sites. No statistically significant differences were observed in comparison to the adsorption coefficients obtained by HPLC. The advantage of the proposed SI-SWV method is the great saving of reagent because it does not use organic solvent as in the case of HPLC (50% (v/v) acetonitrile in the mobile phase). Additionally the start up of SI-SWV is immediate (no column conditioning necessary) and the analysis time is only 19 s.
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Luciana B.O. dos Santos, Gilberto Abate, Jorge C. Masini,