An approach to the calibrationless determination of copper and lead by anodic stripping voltammetry at thin mercury film microelectrodes. Application to well water and rain

A method, not demanding calibration with standard solutions of the analysed ions, is proposed for the determination of lead and copper in synthetic and real samples, by employing thin mercury film electrodes formed onto carbon disc microelectrodes. The method is based on an equation derived by exploiting the characteristics of the in situ thin mercury film formation and steady state currents achievable at microelectrodes. The conditions under which this equation is applicable are examined. In particular the effects of the nature of the electrolyte, with particular concern towards chloride ions, ionic strength and pH of the medium are investigated. The validity of the proposed method is verified on synthetic aqueous solutions. It is shown that the method can be applied to samples characterised either by a low or high ionic strength, while the solutions must be acidic (pH < 6 is recommended) and should not contain more than 1 mM of chloride ions. Real samples, as well water and rain, under conditions fulfilling the above prescriptions, are also investigated. The comparison of data obtained employing the proposed method with those taken, or evaluated by using classical calibration procedures with standard solutions, shows that agreement within 11% is found for 2 and 0.6 μg l−1 levels for lead and copper, respectively, with a relative standard deviation of about 6%. For 10 and 3 μg l−1 levels of lead and copper, respectively, which are the average values in the real samples investigated, both accuracy and RSD are around 5%.