Study of the voltammetric behaviour of metam and its application to an amperometric flow system |
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Authors: | M?Fátima?Barroso Paula?Paíga M?Carmo?V?F?Vaz Email author" target="_blank">Cristina?Delerue-MatosEmail author |
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Institution: | (1) REQUIMTE/Instituto Superior de Engenharia do Porto, Rua Dr. Bernardino de Almeida 431, 4200-072 Porto, Portugal |
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Abstract: | The electrochemical behaviour of the pesticide metam (MT) at a glassy carbon working electrode (GCE) and at a hanging mercury
drop electrode (HMDE) was investigated. Different voltammetric techniques, including cyclic voltammetry (CV) and square wave
voltammetry (SWV), were used. An anodic peak (independent of pH) at +1.46 V vs AgCl/Ag was observed in MT aqueous solution
using the GCE. SWV calibration curves were plotted under optimized conditions (pH 2.5 and frequency 50 Hz), which showed a
linear response for 17–29 mg L−1. Electrochemical reduction was also explored, using the HMDE. A well defined cathodic peak was recorded at −0.72 V vs AgCl/Ag,
dependent on pH. After optimizing the operating conditions (pH 10.1, frequency 150 Hz, potential deposition −0.20 V for 10 s),
calibration curves was measured in the concentration range 2.5×10−1 to 1.0 mg L−1 using SWV. The electrochemical behaviour of this compound facilitated the development of a flow injection analysis (FIA)
system with amperometric detection for the quantification of MT in commercial formulations and spiked water samples. An assessment
of the optimal FIA conditions indicated that the best analytical results were obtained at a potential of +1.30 V, an injection
volume of 207 μL and an overall flow rate of 2.4 ml min−1. Real samples were analysed via calibration curves over the concentration range 1.3×10−2 to 1.3 mg L−1. Recoveries from the real samples (spiked waters and commercial formulations) were between 97.4 and 105.5%. The precision
of the proposed method was evaluated by assessing the relative standard deviation (RSD %) of ten consecutive determinations
of one sample (1.0 mg L−1), and the value obtained was 1.5%. |
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Keywords: | Metam Glassy carbon electrode Hanging mercury drop electrode Flow injection amperometric system |
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