Determination of methoprotryne and terbutryn by adsorptive stripping voltammetry on the hanging mercury drop electrode

Abstract

Sensitive methods for the determination of the herbicides methoprotryne and terbutryn at nanomolar levels, by adsorptive stripping voltammetry at a hanging mercury drop electrode, are described. The electrocapillary curves, and cyclic voltammograms, demonstrate the adsorption of these compounds on the mercury electrode. A systematic study of the various experimental parameters that affect the stripping response was carried out by differential pulse voltammetry. The working medium chosen was 0.1 mol l^–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 × 10^–10 and 2.4 × 10^–9 mol l^–1 for terbutryn and methoprotryne, respectively, and the relative standard deviations (n= 10) were 3.1% and 5.0% at concentration levels of 5.0 × 10^–9 mol l^–1 terbutryn and 1.0 × 10^–8 mol l^–1 methoprotryne, respectively. The degree of interference from some other herbicides on the differential pulse stripping signal for methoprotryne and terbutryn was evaluated. Finally, the methods were applied to the determination of terbutryn and methoprotryne in spiked irrigation and tap waters.