Determination of heavy metal ions by mercury coated polymer/graphite composite electrodes

The use of epoxy/graphite composite electrodes is a well known procedure for determination of heavy metals. Mercury film deposition at epoxy/graphite composite electrodes is a way to improve the performance of the electrodes. In this study, in situ mercury film deposition on the hand-made epoxy/graphite composite electrodes was achieved. After coating the electrode, the determination of Pb2+ and Cu2+ ions on mercury coated epoxy/graphite composite electrode was carried out in 0.1 M HCl media by square wave anodic stripping voltammetry. To improve the performance of the mercury film electrode and the method, optimum experimental conditions were investigated. The effect of the amount of mercury coating, experimental parameters such as accumulation potential and time, potential scan rate on electrode response were studied. The optimum conditions for different concentration levels were determined. At optimum conditions, the mercury film electrode was successfully used to determine ppb levels of Pb2+ in synthetic and real samples. LOD values for ten and three minutes accumulation times were 0.98 ppb and 1.51 ppb, respectively. The analytical response of the electrode against Cu2+ ion was less than that of Pb2+. However, the electrode may be optimized and used for trace determination of Cu2+ in different experimental conditions. Then the reproducibility of the electrode in different concentrations of Pb2+ and reduction times was investigated. For ten and three minutes accumulation time, the relative standard deviations were found to be 13.2% (Pb2+ = 2.1 ppb, n = 17) and 15.3% (Pb2+ = 6.2 ppb, n = 25). The reproducibility was better for more concentrated Pb2+ solutions. The relative standard deviation for three minute accumulation was 3.9% (Pb2+ = 41.4 ppb, n = 10). The method was applied to the determination of lead in real samples of certified waste water standard. The certified lead content was successfully determined in the presence of the other interfering metals.