Determination of the herbicide desmetryne in organised media by adsorptivestripping voltammetry

An electroanalytical method for the determination of the herbicide desmetry ne at nanomolar levels in dispersed media, based on adsorptive stripping vo ltammetry, is reported. The adsorption of desmetryne at the hanging mercury drop electrode was checked both in micellar solutions, where the anionic s urfactant sodium pentanesulphonate was chosen as the most suitable surfacta nt agent, and in oil-in-water emulsions prepared with ethyl acetate as the organic solvent. In a micellar medium formed with 0.02% sodium pentanesulph onate and with 0.1 mol l(-1) Britton-Robinson buffer (pH 1.5), the herbicid e could be determined over the 1.0 x 10(-8)-4.0 x 10(-7) mol l(-1) concentr ation range, when an accumulation potential of -0.70 V was applied for 50 s . On the other hand, in an oil-in-water emulsion formed with 2% ethyl aceta te and 0.04% sodium pentanesulphonate as emulsifying agent in 0.1 mol l(-1) HClO4, desmetryne could be determined over the 2.0 x 10(-9)-1.0 x 10(-7) m ol l(-1) concentration range. The limits of detection were 2.4 x 10(-9) and 4.2 x 10(-10) mol l(-1) in micellar and emulsified media, respectively, wi th R.S.D.s (n = 10) 3.6 and 3.7%. The degree of interference from some othe r s-triazines on the desmetryne differential pulse response was also evalua ted. Finally, the method developed in emulsified medium was applied to the determination of desmetryne in spiked apple juice. (C) 2001 Elsevier Scienc e B.V. All rights reserved.