Trace detection of mercury using boron-doped diamond electrodes

This Project was undertaken to develop electrochemical techniques using Boron-doped Diamond (BDD) electrodes for the purpose of detecting mercury in solutions in the ppb-ppt range. Differential Pulse Voltammetry (DPV) was used successfully to develop calibration curves for mercury detection in standard solutions in the ppb-ppt range, followed by using these curves for mercury measurements in unknown samples. DPV experiments were performed in nitrate, thiocyanate and chloride media. Investigation in the chloride medium is important since practical samples always contain chloride impurities. The formation of calomel in chloride medium is avoided on the BDD surface by the co-deposition of 3ppm of gold during DPV detection. Excellent linear calibration plots have been obtained in all media for ppb ranges. Mercury in the 0.1--50 ppb range has been detected in real samples (KCl impinger solutions) prepared from flue gas released by a pilot-scale coal fired combustion facility. A portable instrument has also been used for the detection of mercury efficiently. BDD mounted in rotating disk electrode (RDE) system together with gold co-deposition has been demonstrated to detect mercury with higher sensitivity and reproducibility. Standard additions method was used for the analysis of unknown samples.