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Abstract: We report the development of a simple analytical method that offers reagentless sensing capabilities by using a copper sensor for monitoring melamine. In this method, the anodic dissolution of the copper electrode is initiated electrochemically to release copper ions, which form the melamine chloride copper ionic pair at the electrode surface. After this process, the melamine chloride copper ionic pair can be reduced electrochemically at the surface of the electrode and quantified under the optimized conditions. This protocol eliminates the necessity to contaminate the sample with a copper salt, making the method proposed herein more environmentally benign than other techniques. The elucidation of the electrochemical reduction process of the melamine copper ionic pair was investigated with an electrochemical quartz crystal microbalance (EQCM). The quantification of melamine in milk was performed using differential pulse voltammetry, where the peak current response was found to increase linearly with melamine concentration over the range 5–90μmolL−1. The repeatability of the electrode response was evaluated as 1% (n=20), and the detection limit of the proposed method was estimated to be 0.85μmolL−1 (3σ/slope). The accuracy of the proposed method was evaluated using milk samples and an addition and recovery protocol. [Copyright &y& Elsevier]

Abstract: Nitrate determination plays a very important role in the analysis of environmental samples. In this paper, an activation procedure for nitrate sensing using a modified copper electrode made from flat flexible cables in presence of a low amount of chloride is reported. The proposed method exhibits enhanced electrocatalytic behaviour in the reduction of nitrate compared to a bare copper electrode. The proposed method showed linear response for nitrate in the concentration range 10–1070μmolL−1, with a regression coefficient R 2 =0.999 (n =12) and a limit of detection of 1.8μmolL−1. According to the procedure based on the standard addition technique, the recovery values obtained were 93–103%, showing the accuracy of the proposed method. In addition, the proposed sensor was applied to the determination of nitrate in mineral water samples and the results are in good agreement (for a 95% confidence level according to the Student's t-test) with those obtained using the capillary electrophoresis procedure. [Copyright &y& Elsevier]

Abstract: A simple and fast electrochemical method for quantitative analysis of picric acid explosive (nitro-explosive) based on its electrochemical reduction at copper surfaces is reported. To achieve a higher sample throughput, the electrochemical sensor was adapted in a flow injection system. Under optimal experimental conditions, the peak current response increases linearly with picric acid concentration over the range of 20–300μmolL−1. The repeatability of the electrode response in the flow injection analysis (FIA) configuration was evaluated as 3% (n=10), and the detection limit of the method was estimated to be 6.0μmolL−1 (S/N=3). The sample throughput under optimised conditions was estimated to be 550 samplesh−1. Peroxide explosives like triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) were tested as potential interfering substances for the proposed method, and no significant interference by these explosives was noticed. The proposed method has interesting analytical parameters, environmental applications, and low cost compared with other electroanalytical methods that have been reported for the quantification of picric acid. Additionally, the possibility to develop an in situ device for the detection of picric acid using a disposable sensor was evaluated. [Copyright &y& Elsevier]