Cathodic Electrochemical Determination of Herbicides in Acid Media Using a Bismuth Film Electrode

Abstract

Abstract 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 μM and the detection limit is 6 μM.