VOLTAMMETRIC DETERMINATION OF A PESTICIDE, SULFOMETURON METHYL, VIA ITS N-CHLORODERIVATIVE

The reported method using differential pulse voltammetry on a platinum electrode allows selective determination of low concentrations of sul fometuron methyl (SMM, weed killer ''Oust'', DuPont). An electroactive species is obtained in an aqueous solution of SMM with NaClO at pH 9. 0. The reaction is characterized by a yellow coloration (lambda(max) = 400 nm) with maximum absorbance measured after 30 min. The reaction p roduct shows a cathodic peak in acidic medium, its current is linearly proportional to the SMM concentration. The potential range (E-pc arou nd 440 mV vs. Ag/AgCl) makes the monitoring highly selective. Oxidatio n of the iodide ion to iodine proves the presence of a 'positive' chlo rine in SMM-Cl. Solid phase extraction of more hydrophobic SMM-Cl, whe n compared with SMM, from aqueous solutions allows a ten-fold increase in sensitivity of the method (ppb range or lower). (C) 1997 Elsevier Science S.A.