Use of a carbon paste modified electrode for the determination of 2-nitrophenol in a flow system by differential pulse voltammetry

The electrochemical reduction of 2-nitrophenol at a bentonite-modified carbon paste electrode by rapid scan differential pulse voltammetry in a flow system is studied, and a method for the direct voltammetric determination in sea water is proposed. A formic acid/sodium formate buffer solution of pH 4 was used as carrier. The potential range and the scan rate were selected according to the response of the analyte. 2-Nitrophenol showed a reduction potential within the cathodic range far the carbon electrode; a well-defined single peak was obtained. It is not necessary to remove the paste from the electrode after each new injection because the surface activity of the electrode remained constant at least during the time of a single complete analysis. A linear relationship between peak height and concentration was obtained in the range 0.05-5 mg l(-1) with a detection limit of 0.02 mg l(-1) and a relative standard deviation of 3.6%. Several chloro- and nitrophenols were tested to assess their influence on 2-nitrophenol signals.