ADSORPTIVE STRIPPING VOLTAMMETRY IN DISPERSED MEDIA - APPLICATION TO THE DETERMINATION OF THE HERBICIDE TERBUTRYN

The possibility of applying adsorptive stripping voltammetry (AdSV) in dispersed media has been evaluated. Sensitive methods for the determination of the herbicide terbutryn at nanomolar levels by AdSV at the hanging mercury drop electrode in micellar and emulsified media are proposed. The anionic surfactant sodium pentanesulfonate was chosen as the most suitable agent for micellar solutions and oil-water emulsions. On the other hand, ethyl acetate was used as the organic solvent to form terbutryn emulsions, a systematic study of the various experimental parameters that affect the stripping response was carried out by differential pulse voltammetry. When working in a 0.1 molL(-1) perchloric acid medium with an accumulation potential of -0.60V, terbutryn could be determined over the 6.0 x 10(-9) -4.0 x 10(-7) and 6.0 x 10(-9) -2.0 x 10(-7) molL(-1) ranges in micellar (50s accumulation time) and emulsified (70s accumulation time) media, respectively. The limits of detection were 2.2 x 10(-9) and 1.1 x 10(-9) molL(-1),and the relative standard deviations (n = 10) were 6.3 and 4.3% in micellar and emulsified media, respectively. The effect of other coexisting herbicides on the terbutryn stripping peak was evaluated. Finally, the developed method in emulsified medium was applied to the determination of terbutryn in spiked tap waters.