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 i n a flow system is studied, and a method for the direct voltammetric d etermination in sea water is proposed. A formic acid/sodium formate bu ffer 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-N itrophenol showed a reduction potential within the cathodic range far the carbon electrode; a well-defined single peak was obtained. It is n ot necessary to remove the paste from the electrode after each new inj ection because the surface activity of the electrode remained constant at least during the time of a single complete analysis. A linear rela tionship between peak height and concentration was obtained in the ran ge 0.05-5 mg l(-1) with a detection limit of 0.02 mg l(-1) and a relat ive standard deviation of 3.6%. Several chloro- and nitrophenols were tested to assess their influence on 2-nitrophenol signals.