DIFFERENTIAL-PULSE VOLTAMMETRIC DETERMINATION OF LEAD(II) WITH BENZOIN OXIME-MODIFIED CARBON-PASTE ELECTRODES

A new chemically modified electrode (CME) for determining lead(II) with high sensitivity and selectivity is reported. The electrode is constructed by adding benzoin oxime into a carbon paste mixture. The lead(II) is accumulated on the electrode surface by the formation of the complex in an open circuit, and then the resulting surface is characterized by medium exchange, potential reduction, and differential pulse anodic stripping voltammetry. In 10 deposition/measurement/regeneration cycles with a single surface, the response could be reproduced with 5.7% relative standard deviation. Quantitation of lead(II) from the peak current of the anodic wave for a 10 minute deposition time gives a detection limit of 8 x 10(-9) M (1.6 ppb). Linear calibration plots are obtained for lead(II) dconcentrations ranging from 10(-7) to 10(-8) M. The modified electrode preferentially accumulates lead from the solution, while most of the metal ions do not interfere with the determination. The mechanism of the accumulation of lead on the benzoin oxime-modified electrode has been explored. Application to the determination of lead in wastewater is illustrated.