Direct determination of trace concentrations of lead in fresh water samples by adsorptive cathodic stripping voltammetry of a lead-Calcein Blue complex

A very sensitive cathodic stripping voltammetric method for the determination of lead, with adsorptive collection of complexes with Calcein Blue (8-[N,N-bis(carboxymethyl)aminomethyl]-4-methylumbelliferone) on to a hanging mercury drop electrode is developed. After accumulation of the complex, the electrode potential is scanned in a negative direction with differential pulse modulation and the reduction current for the lead complex is measured at −0.5 V. Under optimum conditions (300 nM Calcein Blue, pH 6.5, adsorption at −0.15 V), a 3σ limit of detection of 0.04 nM after 1 min collection was obtained. Interference from iron can be decreased by the addition of citrate ion. The method is successfully applied to standard river water SLRS-2 and various fresh water samples.