Utilização de Al2O3 no preparo de amostra para a determinação de glifosato em água : desenvolvimento e validação de método

Abstract

In this paper, a method for determination of glyphosate in water by ionexchange chromatography with conductivity detection (CTI-DC) and high performance liquid chromatography with UV / Vis detection (HPLC-UV / Vis) was developed and validated. Aluminum oxide (Al2O3), whose sorption capacity of the analyte was strongly influenced by the pH of the medium, was used in the preconcentration and clean-up stages; which allowed an effective control of these steps. In the evaluation of the effect of variables such as elution flow and agitation time, a full factorial design was done. Of these, only agitation time had a significant effect (p ≤ 0,05, Student's t) on analyte recovery.. For the determination of glyphosate by CTI-DC, the linear working range was from 0,16 to 1,36 mg L-1, while for determinations by HPLC-UV / Vis this range was from 1,17 to 4,7 mg L-1 for AMPA and glyphosate. The accuracy, expressed in terms of percent recovery, was greater than 84% with lower coefficients of variation (CV) at 19% for both analytical techniques. In the determination by STI-DC, the limits of detection and quantification for glyphosate were 0,002 and 0,02 mg L-1. And in the HPLC-UV / Vis determinations these limits were 0,05 and 0,09 mg L-1 for glyphosate and 0,03 and 0,09 mg L-1 for AMPA. These limits are lower than the reference values established by the United States Environmental Protection Agency (USEPA), which is of 0,7 mg L-1. After validation, the method was applied to samples collected in triplicate in two rivers and two wells in three municipalities in the state of Mato Grosso. No glyphosate residues were detected in any of these samples. The sample preparation method provides accuracy and precision for determination of glyphosate in water samples by CTI-DC and HPLC-UV / Vis, with the advantage of using only water as solvent.