A molecular imprinted electrochemical sensor for the determination of the residue of chlortoluron (CH) in environment was prepared with melamine (MA) as functional monomer. The electropolymerization of poly-melamine-molecularly-imprinted-polymer (PMA-MIP) on the GC electrode was conducted in a 1.0 mol/L H₂SO₄ by cyclic voltammetry (CV) at room temperature (25 ℃). Then the template molecule (CH) on the PMA-MIP film was removed by nitric acid. The experimental conditions (including electrocatalysis of the MA film, pH effects, incubation and competition times) were optimized. The incubation time chosen for the subsequent experiments was 12 min and 12-min was also recommended as the optimized competition time. The Amperometric i-t curves were recorded during the determination. The detection of CH relied on a competition reaction between CH and horseradish peroxidase labeled chlortoluron (HRP-CH) coupled with the subsequent catalytic reduction of hydrogen peroxide by the poly-MA film. Highly sensitive detection of CH was achieved by the double amplification derived from the electro-catalysis of H₂O₂ on MA film and the enzymatic effect of HRP. There was linear relationship between the current changes and CH concentration in the range of 0.01～0.8 μmol/L with a detect limit of 2.64 nmol/L by chronoamperometric method. The proposed PMA-MIP sensor displayed excellent analytical performance (e.g., high sensitivity, good selectivity, and good reproducibility). Some analogues (difenoxuron, neburon, isoproturon and fluometuron) were also used as interferences to examine the selectivity. The changes in the current response of 94-time difenoxuron, 62-time neburon, 38-time fluometuron and 20-time isoproturon are negligible compared with chlortoluron. In addition, the feasibility of its practical applications has been demonstrated in the analysis of samples of tap water and soil extract solution. Recoveries were ranged from 97.0% to 107.0%, and the RSDs were less than 2%, which can be indicators of good recovery and practicability.

Key words: chlortoluron, molecularly imprinted electrochemical sensors, double amplification, poly-melamine, horseradish peroxidase (HRP)