Anodic characterization of mercury microelectrodes for determinations of anions in real samples

The anodization of mercury microelectrodes was investigated in synthetic samples containing several strong and weak electrolytes at different concentrations. In particular, the effects on mercury anodization due to the presence of NaOH, HClO4, NaCl, NaI, NaF, Na2SO4, NaHCO3, Na2CO3, tartaric and citric acids, were studied in solutions containing either each species or mixtures of them, and without addition of supporting electrolyte. Some of the electrode processes studied led to linear calibration plots e.g. 1x10(-5)-1x10(-4) M Cl-, 1x10(-6)-1x10(-5) M I-, 5x10(-4)-3x10(-3) M SO42-, 5x10(-4)-2x10(-2) M HCO3-, with typical correlation coefficients of 0.998-0.999. The anodization of mercury microelectrodes was also investigated directly in wine, rain, tap and mineral water, without pretreatment and without addition of supporting electrolyte. In the real samples only the ions Cl- and HCO3- could be quantified, and the values found were in agreement, within 3-5%, with the reference values obtained by using Italian standard methods for food.