Voltammetric determination of lead (II) in medical lotion and biological samples using chitosan-carbon paste electrode

A simple method for anodic stripping voltammetric determination of lead using carbon paste electrode modified with biomolecular chitosan, is described. In this method, the electrode is activated electrochemically by 5 replicated scanning over the potential range -1000 to -400 mV in 0.5 M HCl solution. Following this step, the lead sample containing 0.1 M KCl solution as supporting electrolyte is purged by nitrogen gas for 2 min, pre-concentrated on the activated electrode at -1000 mV for 30 s. The deposited metal is then oxidized by different modes of sweep in the oxidation direction. Chemical and electrical parameters affecting the voltammetric measurements are optimized. The peak current is proportional to the Pb(II) concentration in a range 10-110 ng/ml, with detection limit 2 ng/m using differential pulse mode. The relative standard deviation is 1.96% for 10 ng/ml ( five replicates). The proposed method is applied to the determination of Pb( II) in acidified samples of tap water, pharmaceutical preparations, human blood and urine with satisfactory results. No interference due to 10 fold excess of Cd, Tl, Sn and Cu is observed. The result obtained by the modified electrode is more accurate and selective than the unmodified electrode.