Voltammetric studies of lead at a 1-(2-pyridylazo)-2-naphthol modified screen-printed carbon electrode and its trace determination in water by stripping voltammetry

A method for the trace determination of Pb2+, using a disposable 1-(2-pyridylazo)-2-naphthol (PAN) drop-coated modified screen-printed carbon electrode (PAN-SPCE), has been developed. Lead ions (Pb2+) are accumulated from ammonia buffer, on the PAN-SPCE surface by the formation of a chemical complex at open circuit. The resulting SPCE with complexed Pb2+ is then transferred to 0.1 M HCl and subjected to differential pulse anodic stripping voltammetry. Conditions were optimised with respect to the pH and concentration of the accumulation medium, preconcentration time and the mass of drop-coated PAN. A 5 min preconcentration time resulted in a limit of detection of 15 ng ml(-1). The calibration plot was found bimodal with linear ranges between 0 and 700 ng ml(-1) and 700-5000 ng ml(-1) Pb2+. The principal metal interference was copper, but this problem was successfully overcome by the addition of iodide to the ammonia buffer prior to the accumulation step. The method was evaluated by carrying out lead determinations on spiked potable water samples; the recovery of Pb2+ was 92.5% and the coefficient of variation was found to be 4.4% (n = 5) using a separate PAN-SPCE for each determination. Therefore, the performance data suggests that the method is reliable at the concentrations examined in this study; in addition, the data compared favorably with that obtained by a published method. (C) 2001 Elsevier Science B.V. All rights reserved.