Determination of sub-nanomolar concentrations of lead in sea water by adsorptive stripping voltammetry with xylenol orange

Highly sensitive procedures are presented for the determination of sub-nanomolar concentrations of total dissolved lead and labile lead in sea water by adsorptive cathodic stripping voltammetry with ligand competition using xylenol orange (XO). Optimal analytical conditions were found to be an XO concentration of 1 × 10−5 M, a pH of 5, and an adsorption potential at −1.2 V vs. AgAgCl with stripping from −0.2 V. The limit of detection for a 180 s stirred adsorption time is 6 ng I−1, making the method amenable to the determination of lead in open ocean waters.