DETERMINATION OF METHOPROTRYNE AND TERBUTRYN BY ADSORPTIVE STRIPPING VOLTAMMETRY ON THE HANGING MERCURY DROP ELECTRODE

Sensitive methods for the determination of the herbicides methoprotryn e and terbutryn at nanomolar levels, by adsorptive stripping voltammet ry at a hanging mercury drop electrode, are described. The electrocapi llary curves, and cyclic voltammograms, demonstrate the adsorption of these compounds on the mercury electrode. A systematic study of the va rious experimental parameters that affect the stripping response was c arried out by differential pulse voltammetry. The working medium chose n was 0.1 mol 1-1 perchloric acid. By using an accumulation potential of -0.70 V and a 180 s accumulation time, the limits of detection were 5.2 x 10(-10) and 2.4 x 10(-9) mol l-1 for terbutryn and methoprotryn e, respectively, and the relative standard deviations (n = 10) were 3. 1% and 5.0% at concentration levels of 5.0 x 10(-9) mol l-1 terbutryn and 1.0 x 10(-8) mol l-1 methoprotryne, respectively. The degree of in terference from some other herbicides on the differential pulse stripp ing signal for methoprotryne and terbutryn was evaluated. Finally, the methods were applied to the determination of terbutryn and methoprotr yne in spiked irrigation and tap waters.