Direct determination of lead by bioaccumulation at a moss-modified carbon paste electrode

Abstract

Mosses are known to accumulate metals by an ion-exchange mechanism. The present work describes the application of a carbon paste electrode modified by Sphagnum Sp. for the determination of lead(II) in natural and drinking waters by anodic stripping differential pulse voltammetry. The preconcentration step is performed under open circuit conditions and the response is evaluated with respect to electrolyte, pH, ionic strength, preconcentration time and lead concentration. The electrode composition, voltammetric waveform and other variables have also been taken into account. For the preconcentration step, the best conditions were acetate buffer of pH 5.0 and 0.01 ionic strength. The supporting electrolyte was acetate buffer of pH 6.0 and 0.7 ionic strength. The modified electrode contained 10% moss. The electrode surface can be regenerated by immersion in 0.05 M perchloric acid for 60 s. The effect of various water components on the voltammetric response was also evaluated. The detection limit was 2 ng ml−1 (15 min preconcentration time). The relative standard deviation was 4.8% for a series of ten measurements of 20 ng ml−1 samples. Direct determination of lead in natural and drinking waters is possible using the standard addition method.