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A rapid multiresidue method has been developed for the analysis of eight pesticides (triazines, triazinones and ureas) in environmental waters. A simple end-column electrochemical detector was used in combination with an available commercial capillary electrophoresis instrument with UV detection. The determination of these pesticides using micellar electrokinetic capillary chromatography (MEKC) with dual electrochemical and UV detection is the first time reported. In both detection systems, a linear range was obtained for the eight pesticides, concentrations lower than 5.0 Â 10 À5 mol L À1, in 0.020 mol L À1 boric acid at pH 8.3 and containing 0.025 mol L À1 of sodium dodecylsulfate, to obtain selectivity in the additional separation by micellar distribution process. Under these conditions a lower detection limit than 2.0 Â 10 À6 mol L À1 (0.15 pmol of pesticide) was achieved for the most of them. The eight pesticides are resolved in less than 14 min.

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A revised procedure for the preparation of bismuth film electrodes (BiFEs), adapted to improve its performance in acid media, is presented and applied for the analysis of herbicides under these conditions. Common carbon-based substrates have been studied for the preparation of ex situ BiFE as well as the influence of relevant parameters upon the bismuth film formation (plating solution, deposition potential and deposition time). A plating solution consisting of 0.60 mM Bi(NO 3 ) 3 in 0.10 M H 2 SO 4 and a careful selection of the plating potential (equal to the cathodic peak potential in this solution) applied during 360 s yields to a suitable BiFE in terms of stability and electroanalytical performance. The applicability of the BiFE was investigated for the analysis of the herbicides metamitron, metribuzin, maleic hydrazide and atrazine in nondeaerated solutions by square-wave voltammetry (SWV). In all cases the enhanced electrochemical performance of the BiFE over bare glassy carbon electrode (GCE) is evident. Herbicides signals at BiFE have improved sensitivity and a positive potential shift is observed when compared to bare GCE. The herbicide metribuzin (4-amino-6-tert-4,5-dihydro-3-methyl-thio-1,2,4-triazin-5-one) was determinated in nondeaerated solutions by square-wave voltammetry (SWV) using BiFE. Under optimal conditions, the dynamic linear range of concentrations is comprised between 10 and 200 mM and the detection limit is 6 mM.