Electrochemical Determination of Mercury at Trace Levels Using Modified Carbon Paste Electrode

A new carbon paste electrode modified with water hyacinth (Eichhornia Crassipes) was developed for the determination of mercury in aqueous sample using differential pulse anodic stripping voltammetry. First mercury was adsorbed on electrode surface at open circuit, following this the adsorbed mercury was determined by anodic stripping voltammetric scan from -0.5 to 0.5 V. Factors affecting sensitivity and precision of the electrodes, including amount of modifier, supporting electrolyte, accumulating solvent, pH of the accumulating solvent, accumulation time and scan rate were investigated. Optimized working conditions are defined as 5 % water hyacinth biomass of graphite powder, sodium hydroxide as supporting electrolyte, acetate buffer of pH 3 as an accumulating solvent and scan rate 50 mV/S. Linear calibration curves were obtained in the concentration range 400 μgL-1 to 800 μgL-1 of mercury for accumulation time of 10 min with limit of detection 195 μgL-1. This technique does not use mercury and therefore, has a positive environmental benefit.