Atrazine interaction with tropical humic substances by Enzyme Linked Immunosorbent AssayI. Toscano1, J. Gascón2, M.-P. Marco3, J.C. Rocha1 and D. Barceló2
1 Department of Analytical Chemistry, UNESP, R. Francisco Degni, s/n 14800-900 Araraquara, Brazil
2 Department of Environmental Chemistry, CID-CSIC, c/ Jordi Girona, 18-26, 08034 Barcelona, Spain
3 Department of Biological Organic Chemistry, CID-CSIC, c/ Jordi Girona, 18-26, 08034 Barcelona, Spain
Enzyme-Linked Immunosorbent Assay (ELISA) has been evaluated by analyzing rich-humic water samples from tropical rivers. The samples were spiked with atrazine at ppb level. Different pHs (4 to 9) and humic concentrations (2.5 to 40 mg L-1) were investigated. The assay performance showed a strong dependence on the pH values and amount of humic matter at low atrazine concentration. From all the conditions studied the low pH (pH 4) and high humic substances concentrations (40 mg L-1) showed the greatest influence. The IC50 value to control sample (no humic) diminished from 0.28 nmol L-1 to 0.64 nmol L-1 to humic acid solution. This effect is specially noted for the humic acid fractions, since fulvic acid fractions showed no significant change on the immunoassay results. Additionally, it has been demonstrated that at basic pH the matrix effect produced by the natural Brazilian water sample containing humic substances even at 40 mg L-1 disappears. Therefore, the ELISA method used to determine atrazine, can be employed to determine this pesticide in water samples containing humic substances without prior preparation.
Key words: Atrazine / aquatic humic substances / immunoassays.
© EDP Sciences, Wiley-VCH 1998