Mercury-free PSA of heavy metals using graphite-epoxy composite electrodes

A potentiometric stripping analysis (PSA) of heavy metals based on a graphite-epoxy composite electrode without surface modification and also without the traditional use of mercury is presented. The graphite-epoxy electrode was used as working electrode in the determination of lead, copper and cadmium in a concentration range from 250 to 2000 ppb. Results for lead determination show the advantages offered by a graphite-epoxy composite as an alternative to mercury-modified carbon electrodes. Advantages include the elimination of the use of environmental harmful mercury or other kind of modifiers while offering a similar sensitivity and repeatability. The limit of detection (LoD) for lead is approximately 200 ppb, with an accumulation time of 60 s. The use of longer deposition times show an increase of peak height and hence a greater sensitivity and a lower LoD. For practical application however it is essential to reach a compromise between sensitivity, LoD and length of analysis time.